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Gallery of Sun images :: NASA Space Place

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Get up close and personal with our own star.

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Where does the sun's energy come from? :: NASA Space Place

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Space Place in a Snap answers this important question!

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The page you are looking for is no longer available. As stated in our communication in January 2018 and subsequent site banners; as of July 31st, 2018 all Free and Classroom Wikis were disabled and are no longer accessible. We thank you for your interest in Wikispaces over the years and wish you all the best with your future endeavours.

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It's all about Earth's tilt!

Many people believe that Earth is closer to the Sun in the summer and that is why it is hotter. And, likewise, they think Earth is farthest from the Sun in the winter.

Although this idea makes sense, it is incorrect.

It is true that Earth's orbit is not a perfect circle. It is a bit lop-sided. During part of the year, Earth is closer to the Sun than at other times. However, in the Northern Hemisphere, we are having winter when Earth is closest to the Sun and summer when it is farthest away! Compared with how far away the Sun is, this change in Earth's distance throughout the year does not make much difference to our weather.

There is a different reason for Earth's seasons.

Earth's axis is an imaginary pole going right through the center of Earth from "top" to "bottom." Earth spins around this pole, making one complete turn each day. That is why we have day and night, and why every part of Earth's surface gets some of each.

Earth has seasons because its axis doesn't stand up straight.

But what caused Earth to tilt?

Long, long ago, when Earth was young, it is thought that something big hit Earth and knocked it off-kilter. So instead of rotating with its axis straight up and down, it leans over a bit.

By the way, that big thing that hit Earth is called Theia. It also blasted a big hole in the surface. That big hit sent a huge amount of dust and rubble into orbit. Most scientists think that that rubble, in time, became our Moon.

As Earth orbits the Sun, its tilted axis always points in the same direction. So, throughout the year, different parts of Earth get the Sun's direct rays.

Sometimes it is the North Pole tilting toward the Sun (around June) and sometimes it is the South Pole tilting toward the Sun (around December).

It is summer in June in the Northern Hemisphere because the Sun's rays hit that part of Earth more directly than at any other time of the year. It is winter in December in the Northern Hemisphere, because that is when it is the South Pole's turn to be tilted toward the Sun.

Earth's lopsided orbit

Earth's perihelion (point closest to Sun) = 91,400,000 miles from Sun

Earth's aphelion (point farthest from Sun) = 94,500,000 miles from Sun

While that is a difference of over 3 million miles, relative to the entire distance, it isn't much.

And, believe it or not, aphelion (when Earth is farthest from the Sun) occurs in July, and perihelion (when we are closest) occurs in January. For those of us who live in the Northern Hemisphere where it's summer in July and winter in January, that seems backwards, doesn't it? That just goes to prove that Earth's distance from the Sun is not the cause of the seasons.

Related Resources for Educators

Seasons (Educator Guide to go with Seasons Spotlite video)
Seasons (Nearpod Lesson to go with Seasons Spotlite video)
Our World: Sun's Position
Sun's Position (Educator Guide to go with Sun's Position Spotlite video)
Sun's Position (Nearpod Lesson to go with Sun's Position Spotlite video)

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Many people believe that Earth is closer to the Sun in the summer and that is why it is hotter. And, likewise, they think Earth is farthest from the Sun in the winter. Although this idea makes sense, it is incorrect. It is true that Earth's orbit is not a perfect circle.

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The moon, lunar phases, tides, lunar exploration.

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Last year I was lucky enough to receive a grant to build an outdoor classroom at my school, so throughout the school year I'll be brainstorming ways to make the most of this new learning space. Living in the hot and urban environment of Doha, Qatar, my students don't have much experience with the outdoors, so I think there's going to be a ton of opportunities for learning across many different disciplines.

One outdoor classroom project that I'm working on right now is the Human Sundial. It's similar to the boring old sundials you're probably familiar with, except that it's your shadow, and not some little stick's, that points towards the correct time. Another cool feature of this type of sundial is that it corrects for the change in shadows over the course of the year. For those interested in details, this kind of sundial is technically known as a analemmatic sundia l; the analemma is the name of the shape created by the apparent movement of the sun's location in the sky over the course of the year.

In this post I'll explain the nuts and bolts of how to make one of these yourself (it's not hard- I just did it this afternoon!), but first I want to share some ideas for how I'm going to use this as a teacher in (whoops- I mean outside of) the classrom.
Teaching with the sundial
Any time a teacher has a cool tool like the human sundial, there's the danger that you assume students will just somehow "get it" when you show it off in some classroom demonstration. Even if the demo has a wow-factor, more often than not students will leave remembering the phenomenon, but not the un-wowing explanation that follows it. So how to prevent this?

First of all, I'm not going to show the students the sundial right away. That would be like starting a mystery movie by revealing the culprit in the first scene- boring! First I want students to discover how tricky telling time with the sun actually is. With my kindergarten students, who are mostly focusing on shadows, we could begin by just tracking the shadow of a stationary object (like a flag pole) throughout the day. Maybe have a student mark the end of the shadow every hour, or if we wanted to get hi-tech we could try a time-lapse video. If we have a few classes do this and compare the data, I think the students will readily realize that shadows point in certain directions and have certain lengths at different times of the day. I could then up the ante for comprehension by having a shadow prediction contest (where will this flagpole's shadow be at 3:30?). The Kgers could then even make their own simple sundial using chalk like I did, and record videos of themselves explaining how it works (assessment, baby!).

For my 5th graders, who also have an astronomy unit and learn about the rotation and revolution of the Earth, I'd like them to learn about the whole analemma effect- how then sun's apparent location and shadows change over the course of the year. It's safe to assume they won't have many prior conceptions about this, and probably think the sun's path in the sky is relatively constant- so I can exploit that misconception for my own devious learning intentions! I plan on installing the human sundial in the outdoor classroom- but without the analemma date thing to stand on. I'll just mark the spot that works in September so the students will be none the wiser when they check it out at the beginning of the year. As time marches on though, the sundial will get worse and worse at time-keeping, and by January it should be downright awful. This would be a great time to raise the alarm and have the student's try to figure out what's going on. To juice this for all it's worth I'll need to make sure there are some grade-level appropriate resources out there that they can use though (any help here would be much appreciated). Then I can use their suggestions and introduce the analemma to fix the sundial.... until next year of course!
Setting up the sundial
I'm no sundial guru, so initially I tried to order up plans for a human sundial from here. Unfortunately, because Qatar's latitude of 25 degrees North is nearly in the tropics the owner actually refused to sell me the plans, even after repeated requests, because he was worried the sundial's accuracy and somehow his company's reputation would be compromised. Whatever. While it's true that in the tropics shadows aren't very long in the summer at high noon, we won't be using our sundial in the summer, and I don't think Kindergarteners will be too concerned with pinpoint accuracy. At any rate- you definitely don't need to go out and spend money on plans for a human sundial, because there are plenty of free resources just a click away. So let's get started...

1. First you need your exact latitude and longitude. You can use a GPS for this, or you can just go to Google Maps, find your location, and then right-click on it and select "What's here?". This will place a little green arrow on your location that you can hover over and get the latitude and longitude. It leaves it up to you to figure out if you're North or South of the equator and East or West of the prime meridian (good luck with that!).

2. You also need to know your time zone (how many hours plus or minus Greenwich mean time), and whether you're currently having daylight savings time. Since Qatar doesn't bother with daylight savings, this doesn't affect me, but it will require some alterations to your sundial if you are in a place that does.

3. Make sure your sundial location is level. You could use one of those bubble-in-liquid carpenter-thingies to do this, or you could do what I did... take a look at your space and say "Looks pretty level to me!".

4. Then you need to find true North. No, you can't use a compass because they point towards magnetic North. There's a variety of ways to figure out true North, but I think the easiest method is using Solar Noon (when the sun is at its highest point on the horizon), because all you need are some household supplies to make a straight shadow at the time of Solar Noon. Here's a good explanation of how to do it. Don't feel like you need to go get all the construction materials though- I hung my weight off an overhead car shade and just traced the shadow with chalk on the pavement.

5. Once you have a true North/South line set up, then you can start setting up the sundial. To get an idea of what the finished product will look like, I recommend checking out the applet on this website which draws the analemmatic sundial for you when you input the above info (see picture below). You can actually print this out and use it as a mini-sundial as well, just make sure to line it up with your true North/South line.

6. So far so good? Now on to the human-sized sundial! The math for creating one of this sundials is pretty complicated, so to avoid crunching the numbers yourself, you can use a spreadsheet like this. This spreadsheet might seem a little daunting at first, but the only info you need to input is the cells in blue on the first sheet. Besides the info above you'll also need to find out your time zone meridian which is the middle longitude for your time zone (you can find this on the picture here, just look at the longitude number above your time zone- for example Qatar's time zone is +3 so the meridian is 45 degrees East). Finally you need to input the gnomon height, which is simply the height of the thing casting the shadow- you!

When the spreadsheet spits out your numbers, just check the pictured sundial on the sheet called "Layout" and make sure it's identical to the mini-sundial made by the applet. If it is, you're ready to start building the real sundial. Start by creating an origin point (like 0,0 on a graph) somewhere in the middle of your true North/South line. Then it's just like making a giant graph- use the x and y coordinates to plot the hour markers, and the x and "date point Z" coordinates to plot the dates. I did mine in chalk first on the pavement to check if it actually works.
For more information on how you can use a human sundial for some great learning activities, check out my follow-up post here.

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Last year I was lucky enough to receive a grant to build an outdoor classroom at my school, so throughout the school year I'll be brainstorming ways to make the most of this new learning space. Living in the hot and urban environment of Doha, Qatar, my students don't have much experience with the outdoors,...

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How Māui Slowed The Sun

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One evening, Māui and his brothers were making a hāngi for their evening meal. They had just finished heating the stones when the sun went down and it quickly became too dark to see. Māui was annoyed with having to eat his food in the dark. He stood in the light of the fire and addressed his people.

"Every day we have to rush to do our chores and gather our food before the sun sets. Why should we be slaves to the sun? I will catch the sun before it rises, and teach it to travel slowly across the sky!"

But one of the brothers was quick to criticise, not believing Māui could possibly do such a thing.

"It would be impossible to catch the sun, he's much bigger than any bird you've ever caught!"

"The heat and flames would surely burn you to death," said another.

"I think he's got sunstroke," another added, and they all laughed.

When they had quietened down, Māui took the sacred jawbone of his ancestor from his belt and waved it in the air.

"I have achieved many things that were thought impossible - gaining fire from Mahuika, catching the greatest fish in the world, descending to the underworld, and many more. With this magic jawbone, gifted by Murirangawhenua, and with your help, I will succeed in conquering the sun!"

The majority of the people agreed that Māui had achieved many great feats, they decided to help Māui in his quest.

The next day Māui and his whānau collected a huge amount of flax, Māui then taught them how to make flax ropes, a skill he learnt when he was in the underworld. They made square shaped ropes, tuamaka, flat ropes, paharahara, and twisted the flax to make round ropes. After five days the ropes were completed and Māui said a special karakia over them.

"Taura nui, taura roa, taura kaha, taura toa, taura here i a Tamanuiterā, whakamaua kia mau kia ita!"

During the night, Māui and his brothers hoisted the ropes and travelled towards the east to where the sun first rises. They hid under trees and bushes during the day, so the sun wouldn't see them approaching. They collected water in calabashes as they travelled, which Māui said was necessary for their task ahead.

On the twelfth night Māui and his brothers arrived at the edge of a huge, red-hot pit, dug deep into the ground. Inside the pit Tamanuiterā, the sun, was sleeping. The brothers were silent, terrified at what might happen if he awoke. Māui immediately ordered his brothers to build four huts around the edges of the pit to hide their long ropes. In front of the huts they used water to soften the clay and build a wall to shelter them. Māui and his brothers then spread their flax ropes into a noose, only just finishing before dawn, when the sun was due to wake.

"When Tamanuiterā rises and his head and shoulders are in the noose I will call for you to pull tight on the ropes," Māui instructed his brothers.

One of the brothers became worried and wanted to run while he still had time.

"Why are we doing this?" he asked another. "It's madness!"

"We'll be burnt alive, if we run now we might escape with our lives!"

The two brothers tried to sneak away but Māui caught sight of them through the corner of his eye.

"If you run now the sun will see you when he rises from his pit. You will be the first ones to die. There is no turning back!"
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The brothers had no time to answer. The sun had begun to wake and was rising from the pit. They quickly ran back to their huts grabbed hold of their ropes and hid behind the wall of clay, trembling as they waited for Māui's orders. Māui hid and watched.

Tamanuiterā slowly emerged from the deep pit, not knowing that a trap was set for him. His head went through the noose and then his shoulders. Māui suddenly jumped from his hut and yelled to his brothers, "Pull on the ropes, now!"

At first the brothers were too scared to come out. Māui yelled again, "Quickly, before it's too late, and we are scorched to death!"

Just then the sun peered down to the edges of the pit and saw Māui standing before him. Tamanuiterā was furious. He hurled a ball of fire towards Māui, but Māui ducked, holding tightly to his rope and once more chanting his karakia:

"Taura nui, taura roa, taura kaha, taura toa, taura here i a Tamanuiterā, whakamaua kia mau kia ita!"

The brothers jumped from their hiding places, grabbing their ropes just before Tamanuiterā could free himself from the noose.

"Aaaarrrhhh!" the sun roared in anger.

Māui fought off the intense heat and moved to the edge of the pit. He raised his magic jawbone above his head and brought it down hard on the sun. The magic forces from the jawbone flashed like a bolt of lightening.

"Why are you doing this to me?" Cried Tamanuiterā.

"From now on you will travel slowly across the sky, never again will the length of our day be dictated by you," Māui replied.

Tamanuiterā tried to struggle free, but again, Māui showed him the power of his magic jawbone. And Tamanuiterā finally gave up the fight.

Māui instructed his brothers to let go of their ropes. Tamanuiterā travelled slowly up into the sky, tired and beaten.

The days became longer for Māui and his people, giving them plenty of time to fish, gather food and do their chores. Māui's power and ability could never be questioned again, he had succeeded in taming the sun. From that day until this, Tamanuiterā has always travelled slowly across the sky.

And this is the story of how Māui slowed the sun.

(c) Wiremu Grace
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One evening, Māui and his brothers were making a hāngi for their evening meal. They had just finished heating the stones when the sun went down and it quickly became too dark to see. Māui was annoyed with having to eat his food in the dark.