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2C How does the environment change based on different areas of the eclipse?

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2C How does the environment change based on different areas of the eclipse?

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This is what plants and animals do during the eclipse. Some animals don’t act normally during the eclipse. For example some run around and others climb trees. Some plants shut down, while others go into night form.

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This article is for students grades 5-8.

An eclipse occurs when one heavenly body such as a moon or planet moves into the shadow of another heavenly body. Let's learn about the two types of eclipses on Earth.

What is a Lunar Eclipse?

The Moon moves in an orbit around Earth. At the same time, Earth orbits the Sun. Sometimes Earth moves between the Sun and the Moon. When this happens, Earth blocks the sunlight that normally is reflected by the Moon. (This sunlight is what causes the Moon to shine.) Instead of light hitting the Moon's surface, Earth's shadow falls on the Moon. This is an eclipse of the Moon, or a lunar eclipse. A lunar eclipse can occur only when the Moon is full.

A lunar eclipse can be seen from Earth at night. There are two types of lunar eclipses:

1. Total lunar eclipse.

2. Partial lunar eclipse.

A total lunar eclipse occurs when the Moon and the Sun are on exact opposite sides of Earth. Although the Moon is in Earth's shadow, some sunlight reaches the Moon. The sunlight passes through Earth's atmosphere, which filters out most of the blue light. This makes the Moon appear red to people on Earth.

A partial lunar eclipse happens when part of the Moon enters Earth's shadow. In a partial eclipse, Earth's shadow appears very dark on the side of the Moon facing Earth. What people see from Earth during a partial lunar eclipse depends on how the Sun, Earth and Moon align.

A lunar eclipse usually lasts for a few hours. At least two partial lunar eclipses happen every year, but total lunar eclipses are rare. It is safe to look at a lunar eclipse.

What is a Solar Eclipse?

Sometimes when the Moon orbits Earth, the Moon moves between the Sun and Earth. When this happens, the Moon blocks the light of the Sun from reaching Earth. This causes an eclipse of the Sun, or a solar eclipse. During a solar eclipse, the Moon casts a shadow onto Earth.

There are three main types of solar eclipses:

1. Total solar eclipse: A total solar eclipse is visible from a small area on Earth. The people who see the total eclipse are in the center of the Moon's shadow when it hits Earth. The sky becomes very dark, as if it were night. For a total eclipse to occur, the Sun, Moon and Earth must be in a direct line.

2. Partial solar eclipse: This happens when the Sun, Moon and Earth are not exactly aligned. The Sun appears to have a dark shadow on a small part of its surface.

3. Annular (an-yə-lər) solar eclipse: An annular eclipse happens when the Moon is farthest from Earth. Because the Moon is farther away, it seems smaller. It does not block the entire view of the Sun. The Moon in front of the Sun looks like a dark disk on top of a larger Sun-colored disk. This creates what looks like a ring around the Moon.

During a solar eclipse, the Moon casts two shadows on Earth.

1. The umbra (əm-brə): This shadow gets smaller as it reaches Earth. It is the dark center of the Moon's shadow. People standing in the umbra will see a total eclipse.

2. The penumbra (pə-ˈnəm-brə): The penumbra gets larger as it reaches Earth. People standing in the penumbra will see a partial eclipse.

Solar eclipses happen every 18 months somewhere on Earth. Unlike lunar eclipses, solar eclipses last only a few minutes.

Never look directly at the Sun: Doing so can permanently damage your eyes! You must use proper safety equipment to look at any type of solar eclipse.

Why Does NASA Study Eclipses?

Hundreds of years ago, when people observed the Moon during an eclipse, they saw Earth's shadow on the Moon and discovered that the Earth is round. Even after all these years, scientists are still learning about the Moon from lunar eclipses. In December 2011, NASA's Lunar Reconnaissance Orbiter gathered data about how quickly the Moon's day side (the side that always faces Earth) cools during a lunar eclipse. NASA can learn what the Moon's surface is made of from this data. If an area of the Moon's surface is flat, it will cool quickly. Scientists use this data to know which areas of the Moon are rough with boulders and which are flat.

Scientists use solar eclipses as an opportunity to study the Sun's corona. The corona is the Sun's top layer. During an annular eclipse, NASA uses ground and space instruments to view the corona when the Moon blocks the Sun's glare.
Remember, never look directly at the Sun: Doing so can permanently damage your eyes!
More about Eclipses
Lunar Eclipses and Solar Eclipses @ NASA Space Place
How Does a Lunar Eclipse Work? Video
What Is an Orbit? Grades 5-8
Read What Is an Eclipse? (Grades K-4)

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An eclipse occurs when one heavenly body such as a moon or planet moves into the shadow of another heavenly body.

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4A How did scientists figure out how to watch the solar eclipse without getting blind?

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4A How did scientists figure out how to watch the solar eclipse without getting blind?

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Scientists figured out how to watch the solar eclipses without going blind.  They did this by studying the damage or burn on people's eyes that did go blind by watching the solar eclipses without the glasses.

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national aeronautics and space administration

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Total Solar Eclipse 2017 - On Monday, August 21, 2017, all of North America will be treated to an eclipse of the sun. Anyone within the path of totality can see one of nature's most awe inspiring sights - a total solar eclipse.

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4B  How many time a solar eclipse occur-and why is this?

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4B  How many time a solar eclipse occur-and why is this?

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A solar eclipse comes 1 time every 18 month. Scientist think they know when the next  solar eclipse is going to be when because of the previous solar eclipse. Scientist say that eclipses occur faster than usual.

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Seeds Foundations of Astronomy, 9th edition

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You should think about eclipse prediction for three reasons. First, it is an important part of the history of science. Second, it illustrates how apparently complex phenomena can be analyzed in terms of cycles. Third, eclipse prediction will exercise your mental muscles and force you to see Earth, the moon, and the sun as objects moving through space.

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4C How do solar eclipses look from other planets?

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4C How do solar eclipses look from other planets?

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Solar eclipses look the same way on other planets as they do on Earth. However, Mars' moons look like there is a hole in the sun. Venus and Mercury do not have moons, so they can not have solar eclipses.

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(Intermediate) >" onclick="window.open(this.href,'win2','status=no,toolbar=no,scrollbars=yes,titlebar=no,menubar=no,resizable=yes,width=640,height=480,directories=no,location=no'); return false;" rel="nofollow">

To have an eclipse the planet has to have a moon. The eclipses vary in nature (total or not) and length depending on how big the satellite and the Sun appear in the sky of a particular planet.

Mercury and Venus cannot have eclipses because they have no moons.

When we have a lunar eclipse, the Moon experiences a solar eclipse. Unlike the solar eclipses on earth, those on the Moon can last for hours. Since one side of the Moon is permanently facing Earth, eclipses can be seen only on that side. Somebody living on the other side wouldn't know that Earth exists at all! This also applies to almost all the moons in the Solar System.

The moons of Mars are very small so you cannot have total eclipses on Mars, just partial ones. The view from those little moons is more interesting: they see Mars eclipsing the Sun very frequently, and during some seasons it happens every day.

All four giant planets (Jupiter, Saturn, Uranus and Neptune) can experience eclipses, since they all have substantial moons and the Sun appears small from them. Eclipses are most common on Jupiter, because its moons orbit in the same plane with the Sun. There are many nice spacecraft photos that show dark shadows of the moons on Jupiter's disk. Unfortunately, since none of the giant planets have solid surfaces (all of their outer parts are composed of gas), one cannot stand on them and watch the eclipses. But their moons have solid surfaces and offer spectacular view. Moons of Jupiter experience eclipses once per each orbit, and those around Saturn can regularly see the Sun being eclipsed by Saturn's rings before and after the regular eclipse.

Pluto has large and close moon Charon that can eclipse its tiny Sun for more than an hour. Due to the large tilt of Charon's orbit and long year of Pluto, eclipses happen only for a couple of years per each century. Pluto and Charon spend several years eclipsing each other every Pluto's day (6.4 Earth days), then there are no eclipses for next 120 years. Since Pluto also turns only one side to Charon (just like all the moons do), only one side of both Pluto and Charon will ever experience eclipses.
This page was last updated June 28, 2015.

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Are there eclipses on other planets? (Intermediate)

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(Intermediate) >" onclick="window.open(this.href,'win2','status=no,toolbar=no,scrollbars=yes,titlebar=no,menubar=no,resizable=yes,width=640,height=480,directories=no,location=no'); return false;" rel="nofollow"> To have an eclipse the planet has to have a moon. The eclipses vary in nature (total or not) and length depending on how big the satellite and the Sun appear in the sky of a particular planet. Mercury and Venus cannot have eclipses because they have no moons.

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4D Does the Solar Eclipse change temperature?

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4D Does the Solar Eclipse change temperature?

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The solar eclipse does change the Earth's temperature because the moon cast a shadow over the earth Changing the temperature. The temperature can drop about 10 degrees or less.   During the eclipses the moon can change the temperature very quickly.

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Eclipse History

The earliest writings we have showing that people paid attention to eclipses in any official way are around 5,000 years old.

In 1999, Irish Archeoastronomer Paul Griffin investigated the Loughcrew Cairn L Megalithic Monument in Ireland, and discovered that a set of spiral-shaped petroglyphs that might correspond to a solar eclipse which occurred on November 30, 3340 BCE. The symbols display a consistent coding of the sun, moon and horizon, and of the 92 tracks of total solar eclipses, only the one for 3340 BCE visible at this site displayed the same geometric relationships.

Ancient Chinese Records - in particular, the Shu Ching-of the solar eclipse that occurred (most likely) on 22
Sun Earth Day 2009 Banner showing path of total solar eclipse across China.
October 2134 B.C.E. include a passage that translates in English to "the Sun and Moon did not meet harmoniously.

In Ancient China, solar and lunar eclipses were regarded as heavenly signs that foretold the future of the Emperor. The ancient Chinese believed that solar eclipses occur when a celestial dragon devours the sun. They also believed that this dragon attacks the Moon during lunar eclipses. In the Chinese language, the term for eclipse was "shi" which also means "to eat".

One ancient Chinese solar eclipse record describes a solar eclipse as "the sun has been eaten". It was a tradition in ancient China to bang drums and pots and make loud noise during eclipses to frighten the dragon away. The Chinese Imperial Emperor Chung K'ang (B.C.E. 2159 - 2146) learned of an eclipse when he heard much noise in the streets as his subjects tried to drive away the dragon that was eating the sun. They were successful, but the Emperor's two court astronomers, Hsi and Ho, were reportedly beheaded for failing to predict the event.

Babylonian Clay Tablets such as the one below, provide physical records of ancient eclipses viewed by humans, in this instance between 518 and 465 BCE. Babylonian astrologers kept careful records of celestial events including the motions of Mercury, Venus, the sun, and the moon on tablets dating from 1700 to 1681 BCE. Later records identified a total solar eclipse on July 31, 1063 BCE, that "turned day into night," and the famous eclipse of June 15, 763 BCE, recorded by Assyrian observers in Nineveh. By carefully noting local lunar and solar eclipses, Babylonian astronomers were able to predict lunar eclipses and later, solar eclipses, with a fair accuracy. Their tool was the so-called Saros-cycle: this is the period of 223 synodic months (or 18 years and 11.3 days) after which lunar and solar eclipses repeat themselves. Ref: http://sunearthday.nasa.gov/2006/locations/babylon.php

There are many stories of how eclipses have been used to foretell important political events, and for nearly all human civilizations with a recorded history, total solar eclipses were regarded with fear and dread prior to the advent of mathematical schemes for predicting when they would occur.

The Ancient Greeks also recorded eclipse events. The poet Archilochus spoke of the total solar eclipse of 6 April 647 B.C.E. in mythic terms:
"There is nothing beyond hope, nothing that can be sworn impossible, nothing wonderful, since Zeus, father of the Olympians, made night from mid-day, hiding the light of the shining Sun, and sore fear came upon men."

Around 460 BCE, the Greek historian, Herodotus wrote that Thales was able to predict the year when a total solar eclipse would occur. Details of how this prediction was made did not survive. The eclipse occurred in either 610 BCE or 585 BCE. Apparently the method used worked only once because what is known of Greek scientific history does not suggest that the method was ever reliably used again. Thales is said to have visited Egypt, and from the empirical rules in use there for land surveying, brought back to Greece the ideas of deductive geometry later codified by Euclid. Before 450 BCE, Meton realized that a single period of 235 lunar months (19 years) would cause the popular lunar calendar to return to synchrony with the solar, seasonal calendar.

At this time, the same lunar phase would be recorded at the same time of the solar calendar year. This period also gives a rough guide to when a lunar eclipse will recur at the same geographic location.

The famous Greek astronomer, Ptolemy (ca 150 CE) recorded his observations of eclipses in the Almagest and showed he had a sophisticated scheme for predicting both lunar and solar eclipses. Ptolemy knew, for example, the details of the orbit of the Moon including its nodal points.

He also knew that the sun must be within 20 degrees 41' of the node point for an eclipse to occur. From this information, Ptolemy figured that up to two solar eclipses could occur within seven months in the same part of the world. Lunar eclipses were especially easy to calculate because of the vast area covered by Earth's shadow on the Moon. Solar eclipses however required much greater knowledge.

So by the Second Century CE, total solar eclipses could be predicted with some reasonable accuracy. For a growing segment of the human population they were no longer messages from hostile gods or supernatural forces, but simply an interesting regularity of the orbits of the Moon and Earth about the Sun.

More Recent Accounts come to us, as well, through numerous writings about eclipses through the ages. The British poet John Milton writes in Paradise Lost;

"As when the Sun, new risen, Looks through the horizontal misty air, Shorn of his beams, or from behind the Moon, In dim eclipse, disastrous twilight sheds On half the nations and with fear of change Perplexes monarchs."

Solar eclipses were by all accounts events of wondrous and magical proportions. Today, of course, we understand eclipses very well. We know how and why they happen, and when and where they happen. We have seen eclipses from space. We have even used eclipses to probe the laws of physics and to discover new worlds outside the Solar System. Still, eclipses of the sun hold their ancient magic and are fascinating to watch.

Many Scientific Discoveries have been made during solar eclipses. The moon's unique ability to cover the sun's disk has allowed investigations of the corona and chromosphere as well as verification of the theory of General Relativity. The following table lists some of these important scientific discoveries. A more complete listing of important solar eclipses in history can be found at https://eclipse.gsfc.nasa.gov/SEhistory/SEhistory.html

Albert Einstein with Sir Arthur Eddington.
Image Credit: Smithsonian.com

The Solar Corona

NASA's SDO Witnesses a Double Eclipse

Historical Eclipse Image Archive

Newspaper Archive

History Along the Track

Eclipses and Music

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national aeronautics and space administration

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Eclipse History | Total Solar Eclipse 2017

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Total Solar Eclipse 2017 - On Monday, August 21, 2017, all of North America will be treated to an eclipse of the sun. Anyone within the path of totality can see one of nature's most awe inspiring sights - a total solar eclipse.

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4E How do animals react to the solar eclipse?

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4E How do animals react to the solar eclipse?

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Animals will act strange during the eclipse. Whales will begin to breach during the eclipse. Birds will return to their nests. Dairy cows will return to their barn. Bees will go to their hives.

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For a few precious minutes on August 21, darkness will descend across the United States as a historic total solar eclipse crosses the continent from coast to coast.

Millions of people already live under the path of totality, and tens of millions more will make the trek to see the moon blot out the sun. Astronomers already expect that this eclipse will be the most witnessed sky-watching event in human history. (See our map of the best places to watch the solar eclipse.)

But according to biologists and long-time eclipse chasers, humans won't be the only ones reacting to the dramatic changes in the sky.

During a total eclipse, the sky darkens to twilight levels and air temperatures drop. Over the centuries, people who have witnessed these effects have also noted that a variety of animals seem to change their behaviors in response.

Reports of unusual animal reactions to solar eclipses date back centuries. One of the earliest stories comes from Italian monk Ristoro d'Arezzo, who described what happened during a total eclipse on June 3, 1239.

As the sun disappeared and the sky turned dark, "all the animals and birds were terrified; and the wild beasts could easily be caught," he wrote.

During an eclipse seen in Portugal on August 21, 1560, astronomer Christoph Clavius wrote that during totality, "stars appeared in the sky and (marvellous to behold) the birds fell down from the sky to the ground in terror of such horrid darkness."

While it's hard to confirm such colorful anecdotes from history, modern astronomers and eclipse chasers have also reported wild and domestic animals noticeably reacting to eclipses: Dairy cows return to the barn, crickets begin chirping, birds either go to roost or become more active, and whales breach in the seas. ( Take our solar eclipse quiz.)

Veteran eclipse-chaser Peter den Hartog traveled to Hungary in 1999 to experience totality, and he remembers seeing various species of birds and bats suddenly appear during totality.

"[Was it because of] the light intensity, or the flies and mosquitoes that came out ... I'm not sure, but I've definitely experienced more activity during eclipses," Hartog says.

Eclipse-chaser and author Dave Balch was in Kona, Hawaii, for the 1991 total eclipse and noticed excited activity among the birds along the pier during the partial phases before and after totality.

"We could hardly hear each other talk! Then came totality - not a sound. It was deathly quiet. The difference between the noise levels before and during totality was stunning."

And eclipse-chaser Tora Greve was on an expedition to Zambia in 2001 when she noticed that, just as the sun disappeared, frogs began making sounds and raptors stopped circling, possibly due to the change in thermals as the air cooled.

Around the water hole where she was standing, she says, giraffes "started running about during the whole totality. When the sun came back, they stopped and began grazing the trees again."

However, collecting scientifically meaningful data on animal reactions to total solar eclipses is tough business. The paths of eclipses are scattered around the world, and many are visible only from remote regions. That makes it hard to obtain anything more than a few data points per event.

"If you really want to study behavior in a comprehensive way, you have to spend a lot of time in the field observing and have rigorous protocols in place," says ecologist Rebecca Johnson at the California Academy of Sciences.

"If you are an animal behavior ecologist setting up to just study effects of solar eclipses, it can be near impossible."

To improve the scientific record, Johnson helped create the Life Responds project, which runs on a dedicated smartphone app called iNaturalist. Her team of biologists and astronomers will use the app to collect data from the millions of people who will witness the eclipse on August 21.

"We created this project that very simply asks people wherever they are-whether they are under totality or partial eclipse-to spend some time outside looking at animals and observing their behavior before, during, and after the eclipse," she says.

The Life Responds team recommends that people who want to take part scout out in advance where they will be watching the eclipse and think about which animals will be around them. For instance, if you happen to be in a suburban backyard or city park, you may be best able to report on urban invertebrates such as ants and spiders.

Anecdotal evidence suggests that orb-weaving spiders destroy their webs during an eclipse, so Johnson recommends finding a web to watch.

"That might be something particularly easy for people to observe," she says, "because [spiders] don't move very far like flying birds, and so there is a higher likelihood of recording slower invertebrate behavior."

The hope is that the Life Responds app will create a meaningful clearinghouse for animal behavior during eclipses that scientists can use to advance their research.

"The collection of observations and looking for patterns is where science begins, and we hope to bring scientists to the data to spur their research moving forward," Johnson says.

"Hopefully we'll end up documenting something that no one has ever seen before."

Andrew Fazekas, the Night Sky Guy, is the author of Star Trek: The Official Guide to Our Universe and host of NG Live! Mankind to Mars presentations. Follow him on Twitter, Facebook, and his website.

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Surprising Ways Animals React to Solar Eclipses

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For a few precious minutes on August 21, darkness will descend across the United States as a historic total solar eclipse crosses the continent from coast to coast. Millions of people already live under the path of totality, and tens of millions more will make the trek to see the moon blot out the sun.

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4F What is the most efficient to watch the Solar Eclipse?

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4F What is the most efficient to watch the Solar Eclipse?

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The most efficient way to watch the solar eclipse is in North Carolina because it's in the Eclipse imaginary line. Always watch the solar eclipse with Eclipse glasses. North Carolina has a lot of events going on in Eclipse dates.

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national aeronautics and space administration

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Total Solar Eclipse 2017 - On Monday, August 21, 2017, all of North America will be treated to an eclipse of the sun. Anyone within the path of totality can see one of nature's most awe inspiring sights - a total solar eclipse.

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3H If your eyes have been damaged by the eclipse, what can you do to fix them?

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3H If your eyes have been damaged by the eclipse, what can you do to fix them?

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The eclipse can damage your eyes. It can damage your retina and cause blurred vision and permanent blindness. To keep eyes protected from the eclipse, wear glasses made for the eclipse. See optometrist if your eyes are damaged by the eclipse.

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3D Why was this eclipse in America and the next eclipse will be in a different country?

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3D Why was this eclipse in America and the next eclipse will be in a different country?

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This eclipse was in America because when the moon blocked the sun the USA was angled towards the sun. The next eclipse will be depending on what angle the Earth is facing the sun.

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(Image: © Miloslav Druckmüller, Peter Aniol, Martin Dietzel, Vojtech Rusin)

Millions of people intend to watch the 2017 total solar eclipse, which will cross the continental U.S. on Aug. 21. Here's how NASA scientists figure out exactly where the moon's shadow will fall on the surface of the Earth, down to the city block.

Space.com talked with NASA's Ernie Wright, who has been producing NASA's visualizations of the celestial event, to learn how satellites mapping the surface of the moon and advances in computing power have made it possible for scientists to predict precisely where on Earth the eclipse will be visible and for exactly how long - with a precision of about 100 meters (330 feet, or about the length of a city block).

Knowing where to watch the eclipse means the difference between seeing totality - when the sun is fully concealed by the moon - and just a partial eclipse, where the moon covers part of the sun but the sky doesn't fully darken. If you're outside the path of totality, the moon's crossing will be just a glancing blow. [ Total Solar Eclipse 2017: When, Where and How to See It (Safely)]

A 19th century technique for predicting the eclipse has scientists using a coordinate system aligned with the shadow of the moon on the Earth, making it easy to determine whether a given observer on the ground was inside or outside the shadow's circle. But that method simplifies the sun-moon-Earth system, and so is accurate to only within a few miles, depending on the location, Wright said.

"That all assumes that the moon is perfectly smooth and that all the observers on the Earth are at sea level," Wright told Space.com. "These are simplifying assumptions; when you have to make these calculations with pencil and paper you need to simplify them a little bit."

"In the space age, we now have really excellent elevation maps of both the moon and the Earth," he said, "and elevations on the moon affect the limb of the moon - this is the edge of the moon's disc as we see it from Earth - so it's kind of bumpy, it's jagged."

The moon's craters and valleys can let glimmers of sunlight by when a simplified model would expect the sun to be completely covered. Maps of the moon weren't precise enough to factor those irregularities in until less than 10 years ago, after NASA's Lunar Reconnaissance Orbiter and Japan's Kayuga probe mapped the moon's surface, Wright said - and the computational power to calculate the strange, polygonal shape the moon's shadow takes because of the way the sun projects through each of its edge's tiny dips.

Similarly, Earth's elevation can have a surprisingly large effect on the visibility of the eclipse - if you're near the edge of the shadow, the elevation can lift you out of it or into it based on the angle of the sun and moon.

"For the Aug. 2017 eclipse, that's going to pass over the Cascades and the Rockies, and lots of observers that are at elevations that are several kilometers," Wright said. "And so the entire umbra, this is the central shadow, will shift to the southeast by several kilometers when you take into account that elevation."

Wright uses elevation data from NASA's Shuttle Radar Topography Mission, which measures the elevation at 1,200 points between each line of latitude or longitude. He also takes into account the precise locations of the Earth, moon and sun at each time, and the time the sunlight takes to travel to the moon and then down to Earth. [ How Long Will the 2017 Solar Eclipse Last? Depends Where You Are]

To factor all of that in, eclipse modelers like Wright use the 19 th-century coordinate system as a starting point, but then calculate the view for millions of simulated observers by working in the profile of the moon, size and angle of the sun in the sky, as well as elevation at each of the points on the ground. That lets them plot out the swath of land that will see an eclipse, and how long it will last at each point. The number of calculations would seem very strange to early eclipse modelers, but isn't unusual for fields like computer graphics.

"We're able to do modern calculations now just because of this confluence of computing power and large datasets describing the shape of the moon and the Earth," Wright said.

"It's just been this confluence of large datasets from remote sensing and computing power that have allowed us to do this in the last 10 years," Wright said. "The animation that I did, that shows the shape of the umbra and all of that stuff, calculated the observer circumstances at half a trillion points - nobody's going to do that by hand. They'd be happy if they could do 10 of them. But computers love to do things over and over again; they never get tired."

But does it make a difference?

Most eclipse viewers head for the center of the path of totality, where the dark sky will last the longest, but some researchers and particularly adventurous spectators aim for the edge, where more interesting effects around the sun's circumference can manifest for longer periods of time: like a "diamond ring" effect or spots of light that look like beads on a necklace. (Space.com columnist Joe Rao discussed the advantages to heading for the eclipse's edge in a recent column.)

"Rather than chasing duration, they're chasing all of these really beautiful effects that happen near the edge, but you need to know where that edge is," Wright said. "If you haven't accounted for elevation, you could be a couple of kilometers away. Or if you haven't accounted for the polygonal shape of the umbra - that polygon shape becomes more extreme near sunrise and sunset - that can also radically affect where that limit line is that you want to be close to."

But just to get near the center line, Wright said, the simplified calculations should suffice. And maps targeted to the 2017 eclipse, like those appearing in eclipse books that show the entire length of the path, would have less than a pixel of difference in their depiction from borders drawn with the 19th century approach.

This eclipse in particular, he said, is pretty head-on - heading slightly inward of the lines on a map is a safe bet. But if you're chasing the edge, you're going to want something more precise.
Email Sarah Lewin at slewin@space.com or follow her @SarahExplains. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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How Scientists Predict the Path of the 2017 Total Solar Eclipse

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(Image: © Miloslav Druckmüller, Peter Aniol, Martin Dietzel, Vojtech Rusin) Millions of people intend to watch the 2017 total solar eclipse, which will cross the continental U.S. on Aug. 21. Here's how NASA scientists figure out exactly where the moon's shadow will fall on the surface of the Earth, down to the city block.

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3C:Why do we have to wear eclipse glasses during the eclipse rather than every day?

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3C:Why do we have to wear eclipse glasses during the eclipse rather than every day?

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We don't have to wear the eclipse glasses every day because the Solar eclipse sends more UV rays. They are very bright and dangerous to look at. Since the glasses are 100,000 times stronger than regular sunglasses it's strong enough to let us look at the Solar Eclipse.

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[/caption]Radiation from the Sun, which is more popularly known as sunlight, is a mixture of electromagnetic waves ranging from infrared (IR) to ultraviolet rays (UV). It of course includes visible light, which is in between IR and UV in the electromagnetic spectrum.

All electromagnetic waves (EM) travel at a speed of approximately 3.0 x 10 ⁸ m/s in vacuum. Although space is not a perfect vacuum, as it is really composed of low-density particles, EM waves, neutrinos, and magnetic fields, it can certainly be approximated as such.

Now, since the average distance between the Earth and the Sun over one Earth orbit is one AU (about 150,000,000,000 m), then it will take about 8 minutes for radiation from the Sun to get to Earth.

Actually, the Sun does not only produce IR, visible light, and UV. Fusion in the core actually gives off high energy gamma rays. However, as the gamma ray photons make their arduous journey to the surface of the Sun, they are continuously absorbed by the solar plasma and re-emitted to lower frequencies. By the time they get to the surface, their frequencies are mostly only within the IR/visible light/UV spectrum.

During solar flares, the Sun also emits X-rays. X-ray radiation from the Sun was first observed by T. Burnight during a V-2 rocket flight. This was later confirmed by Japan's Yohkoh, a satellite launched in 1991.

When electromagnetic radiation from the Sun strikes the Earth's atmosphere, some of it is absorbed while the rest proceed to the Earth's surface. In particular, UV is absorbed by the ozone layer and re-emitted as heat, eventually heating up the stratosphere. Some of this heat is re-radiated to outer space while some is sent to the Earth's surface.

In the meantime, the electromagnetic radiation that wasn't absorbed by the atmosphere proceeds to the Earth's surface and heats it up. Some of this heat stays there while the rest is re-emitted. Upon reaching the atmosphere, part of it gets absorbed and part of it passes through. Naturally, the ones that get absorbed add to the heat already there.

The presence of greenhouse gases make the atmosphere absorb more heat, reducing the fraction of outbound EM waves that pass through. Known as the greenhouse effect, this is the reason why heat can build up some more.

The Earth is not the only planet that experiences the greenhouse effect. Read about the greenhouse effect taking place in Venus here in Universe Today. We've also got an interesting article that talks about a real greenhouse on the Moon by 2014.

Here's a simplified explanation of the greenhouse effect on the EPA's website. There's also NASA's Climate Change page.

Relax and listen to some interesting episodes at Astronomy Cast. Want to know more about Ultraviolet Astronomy? How different is it from Optical Astronomy?

References:
NASA Science: The Electromagnetic Spectrum
NASA Earth Observatory

electromagnetic waves, infrared, radiation from the Sun, ultraviolet, visible light

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caption]Radiation from the Sun, which is more popularly known as sunlight, is a mixture of electromagnetic waves ranging from infrared (IR) to ultraviolet rays (UV). It of course includes visible light, which is in between IR and UV in the electromagnetic spectrum. All electromagnetic waves (EM) travel at a speed of approximately 3.0 x 10 ...

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The solar eclipse is when the earth, moon, and sun are aligned. It happens about every 18 months.This happens because the moon is going slowly in front of the sun, casting a shadow on earth, until the it totally covered.

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On August 21, 2017 an eclipse will take place across the United States. If you could watch the celestial event from space, what would it look like?

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3B How does the solar eclipse affect animals?

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3B How does the solar eclipse affect animals?

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Some of the ways that a solar eclipse affects animal is by making them think that it is turning into night. Since animals have never seen a solar eclipse, some stare and point at it.

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A team of researchers with the Wildlife and Environment Zimbabwe group kept tabs on a variety of species in Mana Pools National Park during a total solar eclipse in June 2001.

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3G How do they make the strongest solar eclipse protection?

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3G How do they make the strongest solar eclipse protection?

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The strongest solar eclipse filters are made using a strong flexible resin infused with carbon particles. The resin is 100,000 times darker than regular sunglasses that blocks out all UV (ultraviolet) rays which dangerous to the eyes.

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People across the United States get the chance to watch a solar eclipse on Monday, Aug. 21. However, it is not safe to view the eclipse without using special, filtered glasses or a solar telescope.

Related: Want to watch the solar eclipse at a viewing party? Here is where you can go in Orange County

Looking at the sun with substandard glasses may cause permanent damage to your eyes. If you haven't purchased eclipse viewers yet, we suggest you purchase from manufacturers or vendors that have been approved by the American Astronomical Society or International Organization for Standardization.

Here's how the rays of the sun might damage your eyes:

(1) Visible light is the portion of the electromagnetic spectrum that we can see.

(2) UVB rays can destroy the outer cells of the cornea - the eye's protective surface - causing pain and blurred vision.

(3) UVA rays damage the eye's lens and can harm the sensitive retina at the back of the eye and the macula, causing macular degeneration and permanent blindness.
HOW SOLAR ECLIPSE LENSES WORK
Typical sunglasses: Are made of glass, plastic or polycarbonate material that blocks out only 10 percent to 20 percent of daylight and most UV rays. Visible light can still pass though.

Solar eclipse glasses: Are typically 100,000 times darker than sunglasses and are made of black polymer, a flexible resin infused with carbon particles. This blocks out all UV rays and nearly all visible light.

Source: Dr. Baruch Kuppermann, UCI; Space.com; NASA and National Park Service

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How the lenses in solar eclipse glasses protect your eyes from the sun

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People across the United States get the chance to watch a solar eclipse on Monday, Aug. 21. However, it is not safe to view the eclipse without using special, filtered glasses or a solar telescope. Related: Want to watch the solar eclipse at a viewing party?

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3A What states have the best view of the solar eclipse and why?

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3A What states have the best view of the solar eclipse and why?

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The best states that have the best view of the solar eclipse is people who are on the path of totality. Because you can see the effects of the solar eclipse in real life.

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On August 21, 2017 an eclipse will take place across the United States. If you could watch the celestial event from space, what would it look like?

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2B What is with the brightness of the sun that makes us need to wear eclipse glasses?

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2B What is with the brightness of the sun that makes us need to wear eclipse glasses?

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The sun is so bright that eclipse glasses are about 100,000 times darker than normal eclipse glasses. Looking at the sun directly can burn up the retina. If the retina burns, it will never heal.

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We know intuitively that staring at the sun is a bad idea, because every time we do it, our eyes water and start to burn. "Solar retinopathy," the formal name for the damage, occurs when ultraviolet light floods the retina, scarring your eyes with something akin to sunburn. As little as two minutes of sun staring can cause permanent damage to the eye.

Usually, the pain of staring at the sun is enough to turn our gaze before we inflict permanent damage on our eyes. And this is why eclipses are uniquely dangerous-when the sun is partially covered, our natural response to look away is dulled, though the risk of injury is not. The eclipse glasses you have been hearing about fix this problem by blocking out almost all violet light, and all ultraviolet light, protecting our eyes from the danger of the sun while allowing us to stare sunward, enjoying the beauty of the eclipse.

Of course, we haven't always known the ins and outs of solar retinopathy. While there aren't well-documented stories of large groups of people sustaining eye damage, one imagines that sort of thing must have happened centuries ago when both knowledge and literacy were in short supply. And even more recently, there is no shortage of people who have suffered injuries because of eclipses.

During the 1976 eclipse, for example, a total of 58 people in Turkey were taken to the doctor and treated for eclipse-related eye damage. While their vision mostly recovered, some patients sustained damage that would stay with them for up to 15 years. Oregon resident Lou Tomososki recently told the Today Show about the vision damage he sustained during a 1962 partial eclipse that affects him to this day. There's even a legend that Isaac Newton himself attempted to watch an eclipse through a mirror and ended up blinding himself for three days. He suffered months of after-images, but eventually his vision recovered.

We haven't always known the ins and outs of solar retinopathy.

Newton perhaps should have known better-scientists who lived before he did figured out how to safely view an eclipse-and it wasn't through a mirror.

In the fourth century, Aristotle revealed how he watched the eclipse in his writings, contemplating how light bends during the events-"Why is it that an eclipse of the sun, if one looks at it through a sieve or through leaves ... the rays are crescent-shaped where they reach the earth?"-outing leaves and pasta colanders as his preferred methods for eclipse viewing. While watching the shadows of an eclipse pass through another object would have protected his eyes, it wouldn't necessarily have been the best show. A better version of this idea came 600 years later when Ibn al-Haytham, an Egyptian scientist, used the first pinhole camera, also known as a "camera obscura," to view the eclipse as safely as we do today. These cameras project the image of the eclipse onto a viewing screen so people don't have to stare directly at the sun to see the show.

But as Aristotle's teacher taught every freshman philosophy class, seeing the shadow of a thing isn't seeing the thing itself. And thus more direct means of viewing were born. In what was the first telescopic viewing of a full solar eclipse, King Louis XIV of France covered his telescope's objective lens with a piece of smoked glass to dilute the harmful light. This method remained popular through the early 19th century. By 1932, smoked glass had started falling out of favor. Steve Ruskin, Ph.D. from Notre Dame and author of America's First Great Eclipse, told me it was then that products like the "Eclipse-o-scope," eyeglasses with protective film covering the eyeholes, came to market, claiming to provide enough protection to look directly into the sun.

Neither smoked glass nor the Eclipse-o-scope were actually fail-proof though. An article published in 1947 in the Journal of School Health by Paul Tower, M.D. , describes vision issues suffered by 32 children who used smoked glass to view the eclipse as it passed over Los Angeles. He concluded that smoked glass, film, and dark sunglasses don't provide sufficient eye protection from the sun. Instead, current eclipse lenses are made from black polymer, a resin containing carbon particles, which is used for all sorts of solar filters.

Smoked glass, film, and dark sunglasses don't provide sufficient eye protection from the sun.

Even more important than containing black polymer, however, is that glasses be ISO 12312-2 certified. This designation, whose requirements are set by the International Organization of Standards, is the one NASA recommends for eclipse glasses. As Rick Fienberg of the American Astronomical Society told , these glasses reduce the sun's brightness by about 500,000 times-compare that to regular sunglasses, which only reduce sunlight by a factor of five.

NASA also recommends purchasing glasses that come with the manufacturer's name and address printed on them. This ISO standard is especially important given the number of "fake" or otherwise ineffective glasses that have been sold on retailers like Amazon. The exact number of fake glasses sold is still unclear, but consider that Elijah Wolfson from Quartz investigated the first 140 eclipse glasses listings on Amazon and found that 21 of them did not claim to have ISO certification. Only 33 of them identified the name of the manufacturer. Worse, some of the glasses that did claim to have ISO certification or were stamped with their company's name were complete fabrications made of substandard material less protective than is necessary.

Just found out the solar eclipse glasses I ordered months ago are likely counterfeit. People have been posing as NASA-approved manufacturers pic.twitter.com/Jw5DVRvQmU
- Ferris Jabr (@ferrisjabr) August 18, 2017

To combat this issue, the AAS has released a list of approved vendors, and, while it recognizes the list is not exhaustive, it recommends buying glasses from a company off of the list. (Amazon has also issued blanket refunds for eclipse glasses, which do not require customers to actually return the glasses.)

Huge demand and unscrupulous sellers have affected the price of eclipse glasses as well. Over the last three weeks, their average price has more than tripled. Which might mean that at this point, your best bet is making your own pinhole camera for safe viewing. Luckily, NASA's got us covered on that front, too.

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A Brief History of Eclipse Glasses and the People Who Forgot to Wear Them

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We know intuitively that staring at the sun is a bad idea, because every time we do it, our eyes water and start to burn. "Solar retinopathy," the formal name for the damage, occurs when ultraviolet light floods the retina, scarring your eyes with something akin to sunburn.

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2H What is the most efficient way for scientists to predict the eclipse? 

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2H What is the most efficient way for scientists to predict the eclipse? 

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The most efficient way for scientists to predict the eclipse is using cycles, algebra, and geometry. They also use the shadow of the moon, coordinates that are accurate within a few miles, and computers with the right software.

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Seeds Foundations of Astronomy, 9th edition

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You should think about eclipse prediction for three reasons. First, it is an important part of the history of science. Second, it illustrates how apparently complex phenomena can be analyzed in terms of cycles. Third, eclipse prediction will exercise your mental muscles and force you to see Earth, the moon, and the sun as objects moving through space.

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2F How can you take a safe picture of the Solar Eclipse.

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2F How can you take a safe picture of the Solar Eclipse.

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The first thing you need to do before you take a picture of the Solar Eclipse is put a filter or lens on your camera (zoom or solar filters). If 99% of the sun is covered and 1% of the sun is still showing you could still be blinded by the limb, the little red light from the sun.

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Wherever you are in the United States, you're going to want to look up, and that's OK. Every astronomer in the country will tell you to enjoy this rare opportunity. No matter what superstitions you've heard, there is no risk to your health due to simply being outside during a total solar eclipse.

But there's one thing you shouldn't do, and that's look at the sun with your naked eye.

The only time you can look at the sun with your naked eye is A) if you're in the path of totality, where the sun will be completely covered by the moon, and B) during those two minutes or less when the sun is completely covered.

During those brief and geographically constrained moments, the brightness of the sun is reduced to that of a full moon, which can be viewed safely without anything over your eyes.

Otherwise, any glimpse of the sun's brightness is not only uncomfortable, it's dangerous.

What happens if you ignore the warnings?

Your face won't melt off, "Raiders of the Lost Ark"-style, but your eyes could be severely damaged. And, yes, you could go blind.

Looking directly at the powerful brightness of the sun can cause damage to the retina, the light-sensitive part of the eye.

"When you look directly at the sun, the intensity of the light and the focus of the light is so great on the retina that it can cook it," said Dr. Christopher Quinn, president of the American Optometric Association. "If the exposure is great enough, that can and will lead to permanent reduction in vision and even blindness."

The retina may translate light into an electrical impulse that the brain understands, but one thing it can't translate to your brain is pain. So even if you're excited about the eclipse and think one brief glimpse at the sun before it completely hides behind the moon is worth it -- it's not. There's no internal trigger that is going to let you know that you've looked at the sun for too long. Any amount of looking at it is too long.

Even the smallest amount of exposure can cause blurry vision or temporary blindness. The problem is, you won't know whether it's temporary.

"It's really impossible for people, when they're in the moment, to make a judgment over brief versus prolonged exposure," Quinn said. "It's never a good idea to view the eclipse without the protection."

Why you need eclipse glasses

No matter how cute or fancy they may be, wearing your favorite pair of sunglasses -- or a whole stack of sunglasses, for any MacGyver wannabes out there -- won't help. You'll need eclipse glasses, which are regulated by an international safety standard. They're cheap and widely available, and some libraries are even providing them free.

Whether you use the cardboard eclipse glasses or a handheld card with a single rectangular view, the most important feature is the filter.

"Filters that meet the ISO 12312-2 standard reduce the sun's brightness to a safe and comfortable level, like that of a full moon, and block harmful ultraviolet and infrared radiation as well," said Rick Fienberg of the American Astronomical Society. "Solar filters that meet this standard are about 100,000 times darker than ordinary sunglasses, and sunglasses don't block infrared radiation."

Unsafe eclipse glasses bearing the ISO logo and certification label have been flooding the market, according the astronomical society. Websites are also displaying false results that claim to show positive test results for glasses they sell.

"The only way you can be sure your solar viewer is safe is to verify that it comes from a reputable manufacturer or one of their authorized dealers," the society said in a recent release. The organization has a list it keeps updated.

To test for safety, the only thing you can see through a safe solar filter is the sun itself. If you look through and the sun is too bright, out of focus or surrounded by a murky haze, or if you can see things like ordinary household lights, the glasses aren't safe.

If you're tempted to reuse eclipse glasses that are three years or older, they were made before the international safety standard was in place and come with a warning that says you can't look through them for more than three minutes at a time. These should be discarded, according to the astronomical society.

Eclipse glasses can be worn over regular eyeglasses, as well.

Viewing safety

If you plan on watching the eclipse through a camera, a telescope or binoculars, buy a solar filter to place on the end of the lens. But do not wear eclipse glasses while looking through any of these.

"The concentrated light from the optics will go right through the filters on the eclipse glasses and cause severe injury to the eye," Fienberg said.

Binoculars do enable you to have an up-close view of the wonders of the eclipse, Fienberg said. Cheap solar filters are available to place on the binoculars, and you may remove them during totality, when the sun is completely blocked from view.

"During totality, the sun is ringed by this spectacular pearly white corona, a beautiful crown around the jet-black silhouette of the moon, with loops and streamers tracing the sun's magnetic field and extending for several solar diameters in every direction," Fienberg said.

Want to go old school and look through welding filters? Make sure they are Shade 12, 13 or 14 -- although some people say Shade 12 leaves the sun too bright and Shade 14 makes the sun too dim, which leaves only the hard-to-find Shade 13 as the Goldilocks filter. Know that most welders' helmets that might be lying around in garages probably won't have those filters.

Here are safety tips to remember, according to the American Astronomical Society:

Always inspect your solar filter before use; if it's scratched, punctured, torn or otherwise damaged, discard it. Read and follow any instructions printed on or packaged with the filter.

Always supervise children using solar filters.

If you normally wear eyeglasses, keep them on. Put your eclipse glasses on over them, or hold your handheld viewer in front of them.

Stand still and cover your eyes with your eclipse glasses or solar viewer before looking up at the bright sun. After looking at the sun, turn away and remove your filter; do not remove it while looking at the sun.

Do not look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars or other optical device.

Similarly, do not look at the sun through a camera, a telescope, binoculars or any other optical device while using your eclipse glasses or handheld solar viewer; the concentrated solar rays could damage the filter and enter your eyes, causing serious injury.

Seek expert advice from an astronomer before using a solar filter with a camera, telescope, binoculars or any other optical device; note that solar filters must be attached to the front of any telescope, binoculars, camera lens or other optics.

If you are inside the path of totality, remove your solar filter only when the moon completely covers the sun's bright face and it suddenly gets quite dark. Experience totality and then, as soon as the bright sun begins to reappear, replace your solar viewer to look at the remaining partial phases.

Outside the path of totality, you must always use a safe solar filter to view the sun directly.

How can kids watch?

Keep an eye on children and make sure they keep their glasses on at all times, perhaps helping to hold the glasses in place.

There are lots of ways to get your kids involved in the eclipse and all it has to offer. They can create their own "pinhole projection" by crossing the outstretched fingers of one hand over the other during the partial eclipse and enjoying the crescent suns that shine through the waffle-like pattern.

"One thing that always gets kids excited at a solar eclipse is to have them look at the shadow of a leafy tree during the partial phases," Fienberg said. "They'll see lots of little crescent suns projected on the ground by the tiny spaces between the leaves."

One thing that people don't need to worry about is shielding their pets from the eclipse. While animals may exhibit strange behavior during the eclipse, they know better -- better than humans, anyway -- than to look up.

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is it dangerous to look at the sun during a solar eclipse? - cnn

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Can you really go blind staring at an eclipse?

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Wherever you are in the United States, you're going to want to look up, and that's OK. Every astronomer in the country will tell you to enjoy this rare opportunity. No matter what superstitions you've heard, there is no risk to your health due to simply being outside during a total solar eclipse.

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2G How does the solar eclipse  change what the sun looks like?

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2G How does the solar eclipse  change what the sun looks like?

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The solar eclipse changes how we see the sun because the moon covers some of the sun. The sun changes colors based on how the moon is shaped.

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This article is for students grades 5-8.

An eclipse occurs when one heavenly body such as a moon or planet moves into the shadow of another heavenly body. Let's learn about the two types of eclipses on Earth.

What is a Lunar Eclipse?

The Moon moves in an orbit around Earth. At the same time, Earth orbits the Sun. Sometimes Earth moves between the Sun and the Moon. When this happens, Earth blocks the sunlight that normally is reflected by the Moon. (This sunlight is what causes the Moon to shine.) Instead of light hitting the Moon's surface, Earth's shadow falls on the Moon. This is an eclipse of the Moon, or a lunar eclipse. A lunar eclipse can occur only when the Moon is full.

A lunar eclipse can be seen from Earth at night. There are two types of lunar eclipses:

1. Total lunar eclipse.

2. Partial lunar eclipse.

A total lunar eclipse occurs when the Moon and the Sun are on exact opposite sides of Earth. Although the Moon is in Earth's shadow, some sunlight reaches the Moon. The sunlight passes through Earth's atmosphere, which filters out most of the blue light. This makes the Moon appear red to people on Earth.

A partial lunar eclipse happens when part of the Moon enters Earth's shadow. In a partial eclipse, Earth's shadow appears very dark on the side of the Moon facing Earth. What people see from Earth during a partial lunar eclipse depends on how the Sun, Earth and Moon align.

A lunar eclipse usually lasts for a few hours. At least two partial lunar eclipses happen every year, but total lunar eclipses are rare. It is safe to look at a lunar eclipse.

What is a Solar Eclipse?

Sometimes when the Moon orbits Earth, the Moon moves between the Sun and Earth. When this happens, the Moon blocks the light of the Sun from reaching Earth. This causes an eclipse of the Sun, or a solar eclipse. During a solar eclipse, the Moon casts a shadow onto Earth.

There are three main types of solar eclipses:

1. Total solar eclipse: A total solar eclipse is visible from a small area on Earth. The people who see the total eclipse are in the center of the Moon's shadow when it hits Earth. The sky becomes very dark, as if it were night. For a total eclipse to occur, the Sun, Moon and Earth must be in a direct line.

2. Partial solar eclipse: This happens when the Sun, Moon and Earth are not exactly aligned. The Sun appears to have a dark shadow on a small part of its surface.

3. Annular (an-yə-lər) solar eclipse: An annular eclipse happens when the Moon is farthest from Earth. Because the Moon is farther away, it seems smaller. It does not block the entire view of the Sun. The Moon in front of the Sun looks like a dark disk on top of a larger Sun-colored disk. This creates what looks like a ring around the Moon.

During a solar eclipse, the Moon casts two shadows on Earth.

1. The umbra (əm-brə): This shadow gets smaller as it reaches Earth. It is the dark center of the Moon's shadow. People standing in the umbra will see a total eclipse.

2. The penumbra (pə-ˈnəm-brə): The penumbra gets larger as it reaches Earth. People standing in the penumbra will see a partial eclipse.

Solar eclipses happen every 18 months somewhere on Earth. Unlike lunar eclipses, solar eclipses last only a few minutes.

Never look directly at the Sun: Doing so can permanently damage your eyes! You must use proper safety equipment to look at any type of solar eclipse.

Why Does NASA Study Eclipses?

Hundreds of years ago, when people observed the Moon during an eclipse, they saw Earth's shadow on the Moon and discovered that the Earth is round. Even after all these years, scientists are still learning about the Moon from lunar eclipses. In December 2011, NASA's Lunar Reconnaissance Orbiter gathered data about how quickly the Moon's day side (the side that always faces Earth) cools during a lunar eclipse. NASA can learn what the Moon's surface is made of from this data. If an area of the Moon's surface is flat, it will cool quickly. Scientists use this data to know which areas of the Moon are rough with boulders and which are flat.

Scientists use solar eclipses as an opportunity to study the Sun's corona. The corona is the Sun's top layer. During an annular eclipse, NASA uses ground and space instruments to view the corona when the Moon blocks the Sun's glare.
Remember, never look directly at the Sun: Doing so can permanently damage your eyes!
More about Eclipses
Lunar Eclipses and Solar Eclipses @ NASA Space Place
How Does a Lunar Eclipse Work? Video
What Is an Orbit? Grades 5-8
Read What Is an Eclipse? (Grades K-4)

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An eclipse occurs when one heavenly body such as a moon or planet moves into the shadow of another heavenly body.

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2E What did the astronauts experience during the solar eclipse on the I.S.S.

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2E What did the astronauts experience during the solar eclipse on the I.S.S.

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Commander Fyodor Yurchikhin,  Peggy Whitson and Randolph Bresnik got to experience a partial solar eclipse.  They were the first ones to see it.  Their experience on the I.S.S. was exciting.

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NASA astronauts orbiting the Earth on the International Space Station will get to see Monday's solar eclipse three times.

In a NASA Facebook session on Friday, astronaut Randy Bresnik stated that since the ISS goes around the Earth every 90 minutes, they'll get to see the event three times.

"The first time will be just off the West Coast, we'll actually cross the path of the sun, and we'll have (a partial) eclipse looking up from the space station," Bresnik said during the session.

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HOW CAN I SEE THE TOTAL SOLAR ECLIPSE?
The crew will see the first partial eclipse, starting at 12:33 a.m EDT. The second chance to see the eclipse, will occur at when the ISS is north of Lake Huron in Canada at 2:23 p.m. EDT and the last will occur at 4:17 p.m. EDT, when the space lab is "just off the East Coast," Bresnik said.

NASA has previously said that the ISS crewmembers will likely not see the total solar eclipse, but instead it will be a partial viewing. "Observing a total solar eclipse from manned spacecraft is difficult though not impossible," NASA stated.

During the session, Bresnik noted that the ISS has "specially equipped cameras that'll have these solar filters on them that allow us to take pictures of the sun. That's going to be pretty neat, we'll have a couple of us shooting that."

WHAT CAUSES A TOTAL SOLAR ECLIPSE?
The total eclipse will start on the Oreon coast at 10:15 a.m. PDT and then end in South Carolina at 2:49 p.m. EDT.

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How NASA astronauts will see the solar eclipse 3 times

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NASA astronauts orbiting the Earth on the International Space Station will get to see Monday's solar eclipse three times. In a NASA Facebook session on Friday, astronaut Randy Bresnik stated that since the ISS goes around the Earth every 90 minutes, they'll get to see the event three times.

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2I What effect does the solar eclipse have on the moon?

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2I What effect does the solar eclipse have on the moon?

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One effect of is that the solar eclipse can cause radiation. Radiation is when the sun gives off electromagnetic waves turning into ultraviolet rays when it lands on the moon. Another fact is heat. Heat can be caused by ultraviolet rays that get absorbed by the moon's shield.

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[/caption]Radiation from the Sun, which is more popularly known as sunlight, is a mixture of electromagnetic waves ranging from infrared (IR) to ultraviolet rays (UV). It of course includes visible light, which is in between IR and UV in the electromagnetic spectrum.

All electromagnetic waves (EM) travel at a speed of approximately 3.0 x 10 ⁸ m/s in vacuum. Although space is not a perfect vacuum, as it is really composed of low-density particles, EM waves, neutrinos, and magnetic fields, it can certainly be approximated as such.

Now, since the average distance between the Earth and the Sun over one Earth orbit is one AU (about 150,000,000,000 m), then it will take about 8 minutes for radiation from the Sun to get to Earth.

Actually, the Sun does not only produce IR, visible light, and UV. Fusion in the core actually gives off high energy gamma rays. However, as the gamma ray photons make their arduous journey to the surface of the Sun, they are continuously absorbed by the solar plasma and re-emitted to lower frequencies. By the time they get to the surface, their frequencies are mostly only within the IR/visible light/UV spectrum.

During solar flares, the Sun also emits X-rays. X-ray radiation from the Sun was first observed by T. Burnight during a V-2 rocket flight. This was later confirmed by Japan's Yohkoh, a satellite launched in 1991.

When electromagnetic radiation from the Sun strikes the Earth's atmosphere, some of it is absorbed while the rest proceed to the Earth's surface. In particular, UV is absorbed by the ozone layer and re-emitted as heat, eventually heating up the stratosphere. Some of this heat is re-radiated to outer space while some is sent to the Earth's surface.

In the meantime, the electromagnetic radiation that wasn't absorbed by the atmosphere proceeds to the Earth's surface and heats it up. Some of this heat stays there while the rest is re-emitted. Upon reaching the atmosphere, part of it gets absorbed and part of it passes through. Naturally, the ones that get absorbed add to the heat already there.

The presence of greenhouse gases make the atmosphere absorb more heat, reducing the fraction of outbound EM waves that pass through. Known as the greenhouse effect, this is the reason why heat can build up some more.

The Earth is not the only planet that experiences the greenhouse effect. Read about the greenhouse effect taking place in Venus here in Universe Today. We've also got an interesting article that talks about a real greenhouse on the Moon by 2014.

Here's a simplified explanation of the greenhouse effect on the EPA's website. There's also NASA's Climate Change page.

Relax and listen to some interesting episodes at Astronomy Cast. Want to know more about Ultraviolet Astronomy? How different is it from Optical Astronomy?

References:
NASA Science: The Electromagnetic Spectrum
NASA Earth Observatory

electromagnetic waves, infrared, radiation from the Sun, ultraviolet, visible light

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caption]Radiation from the Sun, which is more popularly known as sunlight, is a mixture of electromagnetic waves ranging from infrared (IR) to ultraviolet rays (UV). It of course includes visible light, which is in between IR and UV in the electromagnetic spectrum. All electromagnetic waves (EM) travel at a speed of approximately 3.0 x 10 ...

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GROUP DIRECTIONS 1. In the title, write your core number/group letter followed by your essential question.

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GROUP DIRECTIONS 1. In the title, write your core number/group letter followed by your essential question.

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2. In the post body, write a 30-40 word "GIST" of your research answering your essential question.
3. Click + to add a link to the most helpful resource your group used.
4. Edit your post.

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2A Why do our eyes react differently when we are staring at the sun with and without the glasses?

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2A Why do our eyes react differently when we are staring at the sun with and without the glasses?

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The eclipse glasses block out all the ultraviolet light except 0.003% in the eclipse.  Without these protective glasses, the sun can damage your retina. However, you can still see the eclipse.

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If you're going to stare at the sun during the upcoming solar eclipse on August 21, you need eye protection. Unfortunately, obtaining eye protection in recent days has become a major pain. Namely:

Still, there's no excuse for not protecting your eyes if you're going to admire the partial phases of the eclipse, when the sun is not totally covered by the moon. None at all. You either have to find some eclipse glasses, breaking out some very dark welder's glasses, or use an indirect method - like a pinhole projector (more on that below) - to view the eclipse. Because if you don't, you risk permanent eye damage.

So here's a short guide to why staring at the sun is so bad for you, and what you need to look out for when purchasing or using eclipse glasses.

How the sun can burn a hole in your eyeball

The sun is the most powerful source of energy in the solar system. It's the most energetic object for light-years in all directions (it's literally a huge fusion reactor). The energy it expels is so intense it can actually burn holes in your vision.

And it's particularly dangerous because of the anatomy of our eyes, Joel Schuman, chair of ophthalmology at NYU Langone Health, explains. When light enters our eyes, the lens focuses light to the retina, located in the back of the eye. We see thanks to the retina's chemical sensors picking up on the presence of light and transmitting information to the brain.

The retina can handle indirect sunlight just fine. But think of what happens when you hold a magnifying glass up to the sun. It focuses light intensely enough to start a fire.

Something similar happens with the lens in your eye when it's focused directly on the sun.

"The light from the sun is very intense and concentrated into a very small area, and then that light is converted into heat and that heat cooks the retina," Schuman says. "So you have a permanent area that you don't see, a permanent blind spot." What's worse, a retina burn doesn't heal like a sunburn on the skin. It actually doesn't heal at all.

It doesn't heal because the retina is nerve tissue, Schuman explains, which doesn't readily regenerate. Think of it like a spinal cord tear: permanent. And because the light from the sun hits the center of the retina, this burn occludes the sharpest region of central vision. "Oh, 20 seconds probably, that's all it took," Louis Tomososki, an Oregon man who was partially blinded during a total solar eclipse in 1963, told a local NBC affiliate. "Looking at someone and being able see their face - but not their nose" is how he described it to NBC.

In less severe cases, Schuman says, there may just be swelling in the retina. This can be treated with steroids or other anti-inflammatory drugs.

So be sure, if you think your eyes have been damaged, to see a doctor for treatment!

Normally we don't look at the sun because it's uncomfortable. But an eclipse is an opportunity to appreciate our place in the universe.

In 1999, a solar eclipse passed over the United Kingdom. Just one hospital alone in Leicester had 45 patients complaining of eye trouble, the journal Lancet reported. Twenty of the cases involved burns or inflammation to the retina.

So how do eclipse glasses work?

On August 21, a total or partial solar eclipse will be visible from every single US state. But wherever you are, "it is never safe to look directly at the sun's rays - even if the sun is partly obscured," NASA warns. Even when the sun is 99 percent obscured, it can still cause damage.

That's why during a partial eclipse - and even through the early and later phases of a total eclipse, when you can see the last bits of sun peeking through the craters of the moon - you'll need eye protection. You can only take off the protective glasses when the moon has completely covered the sun during totality.

Regular sunglasses won't block enough light. You'll need glasses that filter all but 0.003 percent of visible light and block out most ultraviolet and infrared as well. "Such filters usually have a thin layer of aluminum, chromium or silver deposited on their surfaces that attenuates ultraviolet, visible, and infrared energy," NASA's eye safety page explains. Using photo or X-ray film is not safe.

(The same thing goes for looking through binoculars, mirrored cameras, or telescopes: If you're looking at the sun through them, you'll need to put special filters on the lenses.)

For your eyes, you could grab a pair of one of the darkest available (shade 12 or higher) welder's glasses. Or put on a pair of certified disposable eclipse glasses - the American Astronomical Society points out there are five manufacturers that meet international standards for eclipse eye protection. They are:

When you get glasses, here's the No. 1 thing to look for: Make sure the glasses are certified by the International Organization for Standardization (ISO). The glasses should mark that they meet "ISO 12312-2" safety standards, like so:

Complicating matters: Counterfeits that claim to be ISO-certified have been spotted. (Amazon recently issued refunds for counterfeits or uncertified pairs sold thorough its website.)

"The worst part [about the counterfeits] may be that you're fooled into thinking that you're protected," Schuman says.

To avoid a counterfeit, the American Astronomical Society recommends using glasses purchased from its list of approved, definitely-not-counterfeit vendors. See that list here. You'll want to double-check where your specs came from. If you're in doubt, pick up a new pair (though supplies are starting to run low across the country).

If you can't find a pair to buy, you may be able to pick up one for free at your local library. The Space Science Institute, an education nonprofit, is distributing 2 million pairs of specs to 4,800 libraries across the country. Find out if your local branch has them here. (Though a few libraries have recalled glasses too. So ask.) Also check out Vox's sister site Curbed, which has guides for finding solar eclipse glasses in New York City and Washington, DC. Warby Parker stores are also distributing free solar eclipse glasses.

The safest way to view an eclipse: through a pinhole projector

Or if you don't want to risk looking directly at the sun at all, try making a pinhole projector. All it takes is a piece of paper and a pin. The pinhole mimics the properties of a lens, and it will project the image of the sun onto a flat surface. The Verge has a great, thorough guide on how this all works.

One last tip: If you're in the path of the total solar eclipse, you can take off the protective glasses the moment the moon is covering the sun 100 percent. Actually, if you don't, you'll miss the best part of the whole phenomenon: seeing the sun's outer atmosphere, the corona.

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Why you absolutely cannot stare at the sun without eclipse glasses, explained

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If you're going to stare at the sun during the upcoming solar eclipse on August 21, you need eye protection. Unfortunately, obtaining eye protection in recent days has become a major pain. Namely: Still, there's no excuse for not protecting your eyes if you're going to admire the partial phases of the eclipse, when the sun is not totally covered by the moon.

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1G How does the solar eclipse affect animals' behavior?

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1G How does the solar eclipse affect animals' behavior?

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The eclipse affects animals' behavior by animals thinking it was a daily sunset. For example, chimpanzees change their climbing technique. Scientists noticed that some animals didn't act the same as a daily sunset.

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How do pets, birds and wildlife respond to a solar eclipse? Now is your chance to find out and to share what you observe!

Considering that there's a solar eclipse somewhere on Earth every 18 months, on average, and that humans have studied these celestial events for hundreds of years, you'd think that we know absolutely everything there is to know about solar eclipses. But if you think that, well, you'd be wrong.

Of course.

One of the more obvious questions to investigate is how animals react to a solar eclipse. It may surprise you to learn that few formal observations have been published on this topic. But this egregious oversight means that you, as a citizen scientist, can contribute your observations to the literature.

The California Academy of Sciences is asking citizen scientists to record observations of animal behavior as part of their Life Responds project using their free iNaturalist app. Basically, they are looking to collect behavioral observations of animals (and plants) from the largest geographic area ever covered by observers during any solar eclipse so far.

Specifically, the Life Responds team is asking citizen scientists to download the iNaturalist app and create an account. Choose in advance the animal or plant you will observe so you can practice making observations. On eclipse day, the Life Responds team wants you to make a minimum of three observations: the first will be 30 minutes before totality; the second will during totality; and the third will be 30 minutes after totality. In addition to written notes, your observations can include photographs or video.

Which animal or plant will you choose to observe? Will you go to a zoo, a park, greenhouse or nature area to observe your organism? Will you watch insects or wild birds or livestock near your house? Or perhaps you may instead observe a beloved pet or aquarium fishes? And what sorts of behaviors might you see?

A quick look through the literature indicates that most animals and birds react to a total solar eclipse much like they do to nighttime: for example, bees and ants return to their nests and daytime birds return to their roosts in preparation to sleep; nighttime birds become noisy and active; bats start flying and hunting; mosquitoes start biting; and dairy cattle stop grazing, since they prefer to eat during daylight.

"You can explore this yourself with your own pets, or by watching local wildlife, especially birds," suggests NASA on their website.

As I was looking through the literature, I ran across two particularly interesting observations. First, a team of observers who were in tropical Mexico for the 1994 solar eclipse found that almost all colonial orb-weaving spiders took down their webs within one minute of totality ( ref) -- and this behavioral response was prevented in another group of the same species of spiders by shining a light on them during the eclipse. The authors of that paper also noted that different spider species reacted differently: some began taking down their webs before totality whilst others did not appear to be affected at all.

In my opinion, the most unexpected reactions were shown by a group of 16 captive chimpanzees living in Atlanta, Georgia, during an annular eclipse on May 30, 1984.

"At 1214 hours on the day of the eclipse, when the sky began to darken and the temperature began to decrease, solitary females and females with infants moved to the top of a climbing structure. As the eclipse progressed, additional chimpanzees began to congregate on the climbing structure and to orient their bodies in the direction of the sun and moon," write Jane Branch and Deborah Gust, both of Emory University at the time, in their report ( ref).

"At 1223 hours, during the period of maximum eclipse, the animals continued to orient their bodies toward the sun and moon and to turn their faces upward. One juvenile stood upright and gestured in the direction of the sun and moon."

The authors also noted they'd not seen the chimpanzees behaving similarly during a typical, daily sunset.

After reading that paper, I wondered whether any of those chimpanzees were blinded by the event, but was unable to find any follow-up commentary about that.

The Great American Solar Eclipse, which occurs one week from today on Monday, Aug. 21, will follow a path from the west coast to the east across the United States as depicted in this map (or you can refer to NASA's interactive Google eclipse map):

And this video provides some basic safety information for watching a solar eclipse:
Cited:
George W. Uetz, Craig S. Hieber, Elizabeth M. Jakob, R. Stimson Wilcox, David Kroeger, Andrea McCrate, and Alison M. Mostrom (1994). Behavior of Colonial Orb-weaving Spiders during a Solar Eclipse, Ethology 96: 24-32 | doi: 10.1111/j.1439-0310.1994.tb00878.x

Jane E. Branch and Devorah A. Gust (1986). Effect of Solar Eclipse on the Behavior of a Captive Group of Chimpanzees (Pan troglodytes), American Journal of Primatology 11:367-373 | doi: 10.1002/ajp.1350110407

How Do Animals React To A Total Solar Eclipse? | @GrrlScientist

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How Do Animals React To A Total Solar Eclipse?

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How do pets, birds and wildlife respond to a solar eclipse? Now is your chance to find out and to share what you observe! Considering that there's a solar eclipse somewhere on Earth every 18 months, on average, and that humans have studied these celestial events for hundreds of years, you'd think that we know absolutely everything there is to know about solar eclipses.

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 1F How did the solar eclipse change the way ancient civilizations acted?

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 1F How did the solar eclipse change the way ancient civilizations acted?

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Solar eclipses are when the moon is directly between Earth and the sun. The solar eclipse changed the way ancient civilizations acted by affecting their beliefs, religion, and culture. Ancient civilizations thought that the sun and moon were gods.

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Solar eclipses have been fascinating-and often terrifying-humans throughout the course of history. For the first time in nearly 100 years, a solar eclipse's path of totality, where the entire sun is obscured by the moon, will cross a wide swath of the United States on August 21, 2017. As millions prepare to witness the phenomenon, find out how some early cultures and religions tried to explain and understand a solar eclipse.

Ancient China and the Sun-Eating Dragon

One of the first accounts of an eclipse-though one should note that this might be an old wives tale-dates back to 2136 B.C. Legend has it that the Emperor Chung K'ang executed his royal astronomers, Hi and Ho, for failing to predict an eclipse. While the ancient Chinese might have been able to predict eclipses, their explanation for them was based in lore. They believed that giant beings-either a dog or a dragon-were eating the sun. In fact, the Chinese word for eclipse includes the character "shi," which means "to eat." To scare the beast, the ancient Chinese would bang on drums and make enough noise to chase it away.

Vikings and the Wolf Siblings

As in ancient China on other early cultures, the Vikings believed the sun was being eaten during an eclipse. Their legend involves two wolves, Hati and Skoll, who sought to eat celestial bodies. Skoll sought out the moon, and Hati the sun. When one caught up to its prey, the lights would go out. The Vikings also would make loud noises to scare off the wolves and return the light of the sun or moon. They believed that Ragnarok, or the apocalypse, would occur when the wolves truly devoured the sun and the moon.

Inuits and the Squabbling Siblings

The indigenous Inuits of Greenland, Alaska and the Artic used the legend of two celestial beings, moon god Annigan and his sister, sun goddess Malina to explain both eclipses and the lunar cycle. It all began when Anningan chased Malina after a fight. As he repeatedly pursued her, he forgot to eat and lost weight (symbolized by the moon's waning phase), finally disappearing completely when he stopped to regain his strength-becoming the new moon. A solar eclipse occured when Anningan finally reached Malina, just as the moon caught up with the sun.

The Batammaliba and the First Mothers

The Batammaliba people of Benin and Togo regard eclipses as a time to make peace with family, friends and neighbors. Their legend tells of the first two women in the world, Kuiyecoke and Puka Puka, who eventually became the matriarchs of a village. As the village grew, its inhabitants became more argumentative, quarreling with each other frequently. Kuiyecoke and Puka Puka tried to stop the fighting, but no one would listen, so they darkened the sun and the moon to threaten the villagers. Frightened, the villagers stopped fighting, listened to the women, and made peace offerings to each other to bring back the light-a tradition that continues during eclipses today.

Hinduism and the Disembodied Demon

One of the more graphic eclipse legends can be found in Hindu mythology, where gods and demons worked together to create an elixir of mortality. The demon Rahu, however, was determined to taste of the nectar himself. He donned a disguise and crashed a banquet, but the sun and moon told the god Vishnu of his plans just as he took a sip. Vishnu had Rahu beheaded, but his head (with the bit of elixir) remained immortal while his body died. Rahu's severed head lived on, perpetually chasing after the sun and moon in anger. Occasionally he catches up to them and eats them, but the sun and moon re-emerge quickly because he has no arms to hold them, and the chase begins again.

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How 5 Ancient Cultures Explained Solar Eclipses

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Solar eclipses have been fascinating-and often terrifying-humans throughout the course of history. For the first time in nearly 100 years, a solar eclipse's path of totality, where the entire sun is obscured by the moon, will cross a wide swath of the United States on August 21, 2017.

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1E How does the Solar Eclipse affect plants and animals? How are the effects different for us?

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1E How does the Solar Eclipse affect plants and animals? How are the effects different for us?

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When the moon blocks the light from the sun, some producers die and flowers close up. Non-nocturnal animals sleep.  Others go wild. Humans and animals go blind by looking at the sun, but animals don't look at the eclipse.

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An eclipse takes place when Earth or the moon passes through a shadow of another heavenly body.

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1C- What is the most accurate way to predict an eclipse? 

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1C- What is the most accurate way to predict an eclipse? 

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Astronomers argue that complex technology is the best way to predict an eclipse. Others think using different arithmetics is accurate.  Some think a coordinate system with a complex database is right. Others think the J.P.L femurs system (coordinate grid) is accurate.

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(Image: © Miloslav Druckmüller, Peter Aniol, Martin Dietzel, Vojtech Rusin)

Millions of people intend to watch the 2017 total solar eclipse, which will cross the continental U.S. on Aug. 21. Here's how NASA scientists figure out exactly where the moon's shadow will fall on the surface of the Earth, down to the city block.

Space.com talked with NASA's Ernie Wright, who has been producing NASA's visualizations of the celestial event, to learn how satellites mapping the surface of the moon and advances in computing power have made it possible for scientists to predict precisely where on Earth the eclipse will be visible and for exactly how long - with a precision of about 100 meters (330 feet, or about the length of a city block).

Knowing where to watch the eclipse means the difference between seeing totality - when the sun is fully concealed by the moon - and just a partial eclipse, where the moon covers part of the sun but the sky doesn't fully darken. If you're outside the path of totality, the moon's crossing will be just a glancing blow. [ Total Solar Eclipse 2017: When, Where and How to See It (Safely)]

A 19th century technique for predicting the eclipse has scientists using a coordinate system aligned with the shadow of the moon on the Earth, making it easy to determine whether a given observer on the ground was inside or outside the shadow's circle. But that method simplifies the sun-moon-Earth system, and so is accurate to only within a few miles, depending on the location, Wright said.

"That all assumes that the moon is perfectly smooth and that all the observers on the Earth are at sea level," Wright told Space.com. "These are simplifying assumptions; when you have to make these calculations with pencil and paper you need to simplify them a little bit."

"In the space age, we now have really excellent elevation maps of both the moon and the Earth," he said, "and elevations on the moon affect the limb of the moon - this is the edge of the moon's disc as we see it from Earth - so it's kind of bumpy, it's jagged."

The moon's craters and valleys can let glimmers of sunlight by when a simplified model would expect the sun to be completely covered. Maps of the moon weren't precise enough to factor those irregularities in until less than 10 years ago, after NASA's Lunar Reconnaissance Orbiter and Japan's Kayuga probe mapped the moon's surface, Wright said - and the computational power to calculate the strange, polygonal shape the moon's shadow takes because of the way the sun projects through each of its edge's tiny dips.

Similarly, Earth's elevation can have a surprisingly large effect on the visibility of the eclipse - if you're near the edge of the shadow, the elevation can lift you out of it or into it based on the angle of the sun and moon.

"For the Aug. 2017 eclipse, that's going to pass over the Cascades and the Rockies, and lots of observers that are at elevations that are several kilometers," Wright said. "And so the entire umbra, this is the central shadow, will shift to the southeast by several kilometers when you take into account that elevation."

Wright uses elevation data from NASA's Shuttle Radar Topography Mission, which measures the elevation at 1,200 points between each line of latitude or longitude. He also takes into account the precise locations of the Earth, moon and sun at each time, and the time the sunlight takes to travel to the moon and then down to Earth. [ How Long Will the 2017 Solar Eclipse Last? Depends Where You Are]

To factor all of that in, eclipse modelers like Wright use the 19 th-century coordinate system as a starting point, but then calculate the view for millions of simulated observers by working in the profile of the moon, size and angle of the sun in the sky, as well as elevation at each of the points on the ground. That lets them plot out the swath of land that will see an eclipse, and how long it will last at each point. The number of calculations would seem very strange to early eclipse modelers, but isn't unusual for fields like computer graphics.

"We're able to do modern calculations now just because of this confluence of computing power and large datasets describing the shape of the moon and the Earth," Wright said.

"It's just been this confluence of large datasets from remote sensing and computing power that have allowed us to do this in the last 10 years," Wright said. "The animation that I did, that shows the shape of the umbra and all of that stuff, calculated the observer circumstances at half a trillion points - nobody's going to do that by hand. They'd be happy if they could do 10 of them. But computers love to do things over and over again; they never get tired."

But does it make a difference?

Most eclipse viewers head for the center of the path of totality, where the dark sky will last the longest, but some researchers and particularly adventurous spectators aim for the edge, where more interesting effects around the sun's circumference can manifest for longer periods of time: like a "diamond ring" effect or spots of light that look like beads on a necklace. (Space.com columnist Joe Rao discussed the advantages to heading for the eclipse's edge in a recent column.)

"Rather than chasing duration, they're chasing all of these really beautiful effects that happen near the edge, but you need to know where that edge is," Wright said. "If you haven't accounted for elevation, you could be a couple of kilometers away. Or if you haven't accounted for the polygonal shape of the umbra - that polygon shape becomes more extreme near sunrise and sunset - that can also radically affect where that limit line is that you want to be close to."

But just to get near the center line, Wright said, the simplified calculations should suffice. And maps targeted to the 2017 eclipse, like those appearing in eclipse books that show the entire length of the path, would have less than a pixel of difference in their depiction from borders drawn with the 19th century approach.

This eclipse in particular, he said, is pretty head-on - heading slightly inward of the lines on a map is a safe bet. But if you're chasing the edge, you're going to want something more precise.
Email Sarah Lewin at slewin@space.com or follow her @SarahExplains. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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How Scientists Predict the Path of the 2017 Total Solar Eclipse

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(Image: © Miloslav Druckmüller, Peter Aniol, Martin Dietzel, Vojtech Rusin) Millions of people intend to watch the 2017 total solar eclipse, which will cross the continental U.S. on Aug. 21. Here's how NASA scientists figure out exactly where the moon's shadow will fall on the surface of the Earth, down to the city block.

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1D: How does where you are affect how you see the solar eclipse?

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1D: How does where you are affect how you see the solar eclipse?

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Where the moon and the sun is in space affects how we see the solar eclipse. If you were in the path of totality, it would be darker than it would be not in a full eclipse.

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(Image: © Miloslav Druckmüller, Peter Aniol, Martin Dietzel, Vojtech Rusin)

Millions of people intend to watch the 2017 total solar eclipse, which will cross the continental U.S. on Aug. 21. Here's how NASA scientists figure out exactly where the moon's shadow will fall on the surface of the Earth, down to the city block.

Space.com talked with NASA's Ernie Wright, who has been producing NASA's visualizations of the celestial event, to learn how satellites mapping the surface of the moon and advances in computing power have made it possible for scientists to predict precisely where on Earth the eclipse will be visible and for exactly how long - with a precision of about 100 meters (330 feet, or about the length of a city block).

Knowing where to watch the eclipse means the difference between seeing totality - when the sun is fully concealed by the moon - and just a partial eclipse, where the moon covers part of the sun but the sky doesn't fully darken. If you're outside the path of totality, the moon's crossing will be just a glancing blow. [ Total Solar Eclipse 2017: When, Where and How to See It (Safely)]

A 19th century technique for predicting the eclipse has scientists using a coordinate system aligned with the shadow of the moon on the Earth, making it easy to determine whether a given observer on the ground was inside or outside the shadow's circle. But that method simplifies the sun-moon-Earth system, and so is accurate to only within a few miles, depending on the location, Wright said.

"That all assumes that the moon is perfectly smooth and that all the observers on the Earth are at sea level," Wright told Space.com. "These are simplifying assumptions; when you have to make these calculations with pencil and paper you need to simplify them a little bit."

"In the space age, we now have really excellent elevation maps of both the moon and the Earth," he said, "and elevations on the moon affect the limb of the moon - this is the edge of the moon's disc as we see it from Earth - so it's kind of bumpy, it's jagged."

The moon's craters and valleys can let glimmers of sunlight by when a simplified model would expect the sun to be completely covered. Maps of the moon weren't precise enough to factor those irregularities in until less than 10 years ago, after NASA's Lunar Reconnaissance Orbiter and Japan's Kayuga probe mapped the moon's surface, Wright said - and the computational power to calculate the strange, polygonal shape the moon's shadow takes because of the way the sun projects through each of its edge's tiny dips.

Similarly, Earth's elevation can have a surprisingly large effect on the visibility of the eclipse - if you're near the edge of the shadow, the elevation can lift you out of it or into it based on the angle of the sun and moon.

"For the Aug. 2017 eclipse, that's going to pass over the Cascades and the Rockies, and lots of observers that are at elevations that are several kilometers," Wright said. "And so the entire umbra, this is the central shadow, will shift to the southeast by several kilometers when you take into account that elevation."

Wright uses elevation data from NASA's Shuttle Radar Topography Mission, which measures the elevation at 1,200 points between each line of latitude or longitude. He also takes into account the precise locations of the Earth, moon and sun at each time, and the time the sunlight takes to travel to the moon and then down to Earth. [ How Long Will the 2017 Solar Eclipse Last? Depends Where You Are]

To factor all of that in, eclipse modelers like Wright use the 19 th-century coordinate system as a starting point, but then calculate the view for millions of simulated observers by working in the profile of the moon, size and angle of the sun in the sky, as well as elevation at each of the points on the ground. That lets them plot out the swath of land that will see an eclipse, and how long it will last at each point. The number of calculations would seem very strange to early eclipse modelers, but isn't unusual for fields like computer graphics.

"We're able to do modern calculations now just because of this confluence of computing power and large datasets describing the shape of the moon and the Earth," Wright said.

"It's just been this confluence of large datasets from remote sensing and computing power that have allowed us to do this in the last 10 years," Wright said. "The animation that I did, that shows the shape of the umbra and all of that stuff, calculated the observer circumstances at half a trillion points - nobody's going to do that by hand. They'd be happy if they could do 10 of them. But computers love to do things over and over again; they never get tired."

But does it make a difference?

Most eclipse viewers head for the center of the path of totality, where the dark sky will last the longest, but some researchers and particularly adventurous spectators aim for the edge, where more interesting effects around the sun's circumference can manifest for longer periods of time: like a "diamond ring" effect or spots of light that look like beads on a necklace. (Space.com columnist Joe Rao discussed the advantages to heading for the eclipse's edge in a recent column.)

"Rather than chasing duration, they're chasing all of these really beautiful effects that happen near the edge, but you need to know where that edge is," Wright said. "If you haven't accounted for elevation, you could be a couple of kilometers away. Or if you haven't accounted for the polygonal shape of the umbra - that polygon shape becomes more extreme near sunrise and sunset - that can also radically affect where that limit line is that you want to be close to."

But just to get near the center line, Wright said, the simplified calculations should suffice. And maps targeted to the 2017 eclipse, like those appearing in eclipse books that show the entire length of the path, would have less than a pixel of difference in their depiction from borders drawn with the 19th century approach.

This eclipse in particular, he said, is pretty head-on - heading slightly inward of the lines on a map is a safe bet. But if you're chasing the edge, you're going to want something more precise.
Email Sarah Lewin at slewin@space.com or follow her @SarahExplains. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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How Scientists Predict the Path of the 2017 Total Solar Eclipse

# data[].attributes.attachment_link.description
(Image: © Miloslav Druckmüller, Peter Aniol, Martin Dietzel, Vojtech Rusin) Millions of people intend to watch the 2017 total solar eclipse, which will cross the continental U.S. on Aug. 21. Here's how NASA scientists figure out exactly where the moon's shadow will fall on the surface of the Earth, down to the city block.

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1B How can being color blind affect how you see a solar eclipse?

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1B How can being color blind affect how you see a solar eclipse?

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You may see a partial eclipse a little different, the sun will be a little faded but not a lot of change. There will see no change in totality. You would be affected the same way as a normal person.

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Wherever you are in the United States, you're going to want to look up, and that's OK. Every astronomer in the country will tell you to enjoy this rare opportunity. No matter what superstitions you've heard, there is no risk to your health due to simply being outside during a total solar eclipse.

But there's one thing you shouldn't do, and that's look at the sun with your naked eye.

The only time you can look at the sun with your naked eye is A) if you're in the path of totality, where the sun will be completely covered by the moon, and B) during those two minutes or less when the sun is completely covered.

During those brief and geographically constrained moments, the brightness of the sun is reduced to that of a full moon, which can be viewed safely without anything over your eyes.

Otherwise, any glimpse of the sun's brightness is not only uncomfortable, it's dangerous.

What happens if you ignore the warnings?

Your face won't melt off, "Raiders of the Lost Ark"-style, but your eyes could be severely damaged. And, yes, you could go blind.

Looking directly at the powerful brightness of the sun can cause damage to the retina, the light-sensitive part of the eye.

"When you look directly at the sun, the intensity of the light and the focus of the light is so great on the retina that it can cook it," said Dr. Christopher Quinn, president of the American Optometric Association. "If the exposure is great enough, that can and will lead to permanent reduction in vision and even blindness."

The retina may translate light into an electrical impulse that the brain understands, but one thing it can't translate to your brain is pain. So even if you're excited about the eclipse and think one brief glimpse at the sun before it completely hides behind the moon is worth it -- it's not. There's no internal trigger that is going to let you know that you've looked at the sun for too long. Any amount of looking at it is too long.

Even the smallest amount of exposure can cause blurry vision or temporary blindness. The problem is, you won't know whether it's temporary.

"It's really impossible for people, when they're in the moment, to make a judgment over brief versus prolonged exposure," Quinn said. "It's never a good idea to view the eclipse without the protection."

Why you need eclipse glasses

No matter how cute or fancy they may be, wearing your favorite pair of sunglasses -- or a whole stack of sunglasses, for any MacGyver wannabes out there -- won't help. You'll need eclipse glasses, which are regulated by an international safety standard. They're cheap and widely available, and some libraries are even providing them free.

Whether you use the cardboard eclipse glasses or a handheld card with a single rectangular view, the most important feature is the filter.

"Filters that meet the ISO 12312-2 standard reduce the sun's brightness to a safe and comfortable level, like that of a full moon, and block harmful ultraviolet and infrared radiation as well," said Rick Fienberg of the American Astronomical Society. "Solar filters that meet this standard are about 100,000 times darker than ordinary sunglasses, and sunglasses don't block infrared radiation."

Unsafe eclipse glasses bearing the ISO logo and certification label have been flooding the market, according the astronomical society. Websites are also displaying false results that claim to show positive test results for glasses they sell.

"The only way you can be sure your solar viewer is safe is to verify that it comes from a reputable manufacturer or one of their authorized dealers," the society said in a recent release. The organization has a list it keeps updated.

To test for safety, the only thing you can see through a safe solar filter is the sun itself. If you look through and the sun is too bright, out of focus or surrounded by a murky haze, or if you can see things like ordinary household lights, the glasses aren't safe.

If you're tempted to reuse eclipse glasses that are three years or older, they were made before the international safety standard was in place and come with a warning that says you can't look through them for more than three minutes at a time. These should be discarded, according to the astronomical society.

Eclipse glasses can be worn over regular eyeglasses, as well.

Viewing safety

If you plan on watching the eclipse through a camera, a telescope or binoculars, buy a solar filter to place on the end of the lens. But do not wear eclipse glasses while looking through any of these.

"The concentrated light from the optics will go right through the filters on the eclipse glasses and cause severe injury to the eye," Fienberg said.

Binoculars do enable you to have an up-close view of the wonders of the eclipse, Fienberg said. Cheap solar filters are available to place on the binoculars, and you may remove them during totality, when the sun is completely blocked from view.

"During totality, the sun is ringed by this spectacular pearly white corona, a beautiful crown around the jet-black silhouette of the moon, with loops and streamers tracing the sun's magnetic field and extending for several solar diameters in every direction," Fienberg said.

Want to go old school and look through welding filters? Make sure they are Shade 12, 13 or 14 -- although some people say Shade 12 leaves the sun too bright and Shade 14 makes the sun too dim, which leaves only the hard-to-find Shade 13 as the Goldilocks filter. Know that most welders' helmets that might be lying around in garages probably won't have those filters.

Here are safety tips to remember, according to the American Astronomical Society:

Always inspect your solar filter before use; if it's scratched, punctured, torn or otherwise damaged, discard it. Read and follow any instructions printed on or packaged with the filter.

Always supervise children using solar filters.

If you normally wear eyeglasses, keep them on. Put your eclipse glasses on over them, or hold your handheld viewer in front of them.

Stand still and cover your eyes with your eclipse glasses or solar viewer before looking up at the bright sun. After looking at the sun, turn away and remove your filter; do not remove it while looking at the sun.

Do not look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars or other optical device.

Similarly, do not look at the sun through a camera, a telescope, binoculars or any other optical device while using your eclipse glasses or handheld solar viewer; the concentrated solar rays could damage the filter and enter your eyes, causing serious injury.

Seek expert advice from an astronomer before using a solar filter with a camera, telescope, binoculars or any other optical device; note that solar filters must be attached to the front of any telescope, binoculars, camera lens or other optics.

If you are inside the path of totality, remove your solar filter only when the moon completely covers the sun's bright face and it suddenly gets quite dark. Experience totality and then, as soon as the bright sun begins to reappear, replace your solar viewer to look at the remaining partial phases.

Outside the path of totality, you must always use a safe solar filter to view the sun directly.

How can kids watch?

Keep an eye on children and make sure they keep their glasses on at all times, perhaps helping to hold the glasses in place.

There are lots of ways to get your kids involved in the eclipse and all it has to offer. They can create their own "pinhole projection" by crossing the outstretched fingers of one hand over the other during the partial eclipse and enjoying the crescent suns that shine through the waffle-like pattern.

"One thing that always gets kids excited at a solar eclipse is to have them look at the shadow of a leafy tree during the partial phases," Fienberg said. "They'll see lots of little crescent suns projected on the ground by the tiny spaces between the leaves."

One thing that people don't need to worry about is shielding their pets from the eclipse. While animals may exhibit strange behavior during the eclipse, they know better -- better than humans, anyway -- than to look up.

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is it dangerous to look at the sun during a solar eclipse? - cnn

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Can you really go blind staring at an eclipse?

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Wherever you are in the United States, you're going to want to look up, and that's OK. Every astronomer in the country will tell you to enjoy this rare opportunity. No matter what superstitions you've heard, there is no risk to your health due to simply being outside during a total solar eclipse.

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1A  How did Ancient Asian cultures react/feel about total Solar Eclipses?

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1A  How did Ancient Asian cultures react/feel about total Solar Eclipses?

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Cultures were both scared and excited about upcoming eclipses. Some were frightened by the stories of beasts and monsters that would come to eat the sun. They believed it foretold the health, success or doom of an emperor/king.

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Solar eclipses have been fascinating-and often terrifying-humans throughout the course of history. For the first time in nearly 100 years, a solar eclipse's path of totality, where the entire sun is obscured by the moon, will cross a wide swath of the United States on August 21, 2017. As millions prepare to witness the phenomenon, find out how some early cultures and religions tried to explain and understand a solar eclipse.

Ancient China and the Sun-Eating Dragon

One of the first accounts of an eclipse-though one should note that this might be an old wives tale-dates back to 2136 B.C. Legend has it that the Emperor Chung K'ang executed his royal astronomers, Hi and Ho, for failing to predict an eclipse. While the ancient Chinese might have been able to predict eclipses, their explanation for them was based in lore. They believed that giant beings-either a dog or a dragon-were eating the sun. In fact, the Chinese word for eclipse includes the character "shi," which means "to eat." To scare the beast, the ancient Chinese would bang on drums and make enough noise to chase it away.

Vikings and the Wolf Siblings

As in ancient China on other early cultures, the Vikings believed the sun was being eaten during an eclipse. Their legend involves two wolves, Hati and Skoll, who sought to eat celestial bodies. Skoll sought out the moon, and Hati the sun. When one caught up to its prey, the lights would go out. The Vikings also would make loud noises to scare off the wolves and return the light of the sun or moon. They believed that Ragnarok, or the apocalypse, would occur when the wolves truly devoured the sun and the moon.

Inuits and the Squabbling Siblings

The indigenous Inuits of Greenland, Alaska and the Artic used the legend of two celestial beings, moon god Annigan and his sister, sun goddess Malina to explain both eclipses and the lunar cycle. It all began when Anningan chased Malina after a fight. As he repeatedly pursued her, he forgot to eat and lost weight (symbolized by the moon's waning phase), finally disappearing completely when he stopped to regain his strength-becoming the new moon. A solar eclipse occured when Anningan finally reached Malina, just as the moon caught up with the sun.

The Batammaliba and the First Mothers

The Batammaliba people of Benin and Togo regard eclipses as a time to make peace with family, friends and neighbors. Their legend tells of the first two women in the world, Kuiyecoke and Puka Puka, who eventually became the matriarchs of a village. As the village grew, its inhabitants became more argumentative, quarreling with each other frequently. Kuiyecoke and Puka Puka tried to stop the fighting, but no one would listen, so they darkened the sun and the moon to threaten the villagers. Frightened, the villagers stopped fighting, listened to the women, and made peace offerings to each other to bring back the light-a tradition that continues during eclipses today.

Hinduism and the Disembodied Demon

One of the more graphic eclipse legends can be found in Hindu mythology, where gods and demons worked together to create an elixir of mortality. The demon Rahu, however, was determined to taste of the nectar himself. He donned a disguise and crashed a banquet, but the sun and moon told the god Vishnu of his plans just as he took a sip. Vishnu had Rahu beheaded, but his head (with the bit of elixir) remained immortal while his body died. Rahu's severed head lived on, perpetually chasing after the sun and moon in anger. Occasionally he catches up to them and eats them, but the sun and moon re-emerge quickly because he has no arms to hold them, and the chase begins again.

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How 5 Ancient Cultures Explained Solar Eclipses

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Solar eclipses have been fascinating-and often terrifying-humans throughout the course of history. For the first time in nearly 100 years, a solar eclipse's path of totality, where the entire sun is obscured by the moon, will cross a wide swath of the United States on August 21, 2017.