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Tide = A tide is the periodic rising and falling of Earth's ocean surface caused mainly by the gravitational pull of the Moon acting on the oceans. 

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Tide = A tide is the periodic rising and falling of Earth's ocean surface caused mainly by the gravitational pull of the Moon acting on the oceans. 

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How does the Moon cause Tides? + more videos | #aumsum #kids #science #education #children

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A group or parts that work together as a whole

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A group or parts that work together as a whole

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Earth's system constantly cycles energy and matter throughout its spheres.

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covers 3/4 of Earth's surface and contains the oceans, glaciers, rivers, lakes, ground water and even water vapor

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covers 3/4 of Earth's surface and contains the oceans, glaciers, rivers, lakes, ground water and even water vapor

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The most dense (thick) part of Earth's outer layer that includes rocks, crust, solid middle layer or mantle, and the metal core

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The part of Earth's system that contains all living things

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The part of Earth's system that contains all living things

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The capacity of doing work.

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Constructive versus Destructive forces = 

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Constructive versus Destructive forces = 

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Clear liquid that forms lakes, streams, seas, clouds as rain, and is used for drinking, washing etc.

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Clear liquid that forms lakes, streams, seas, clouds as rain, and is used for drinking, washing etc.

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Earth has 3 unique physical characteristics that support life.. they are:

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Earth has 3 unique physical characteristics that support life.. they are:

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1) balance of gases in the atmosphere allowing the breathing of oxygen
2)presence of water
3)temperature that is not too hot or too cold

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The grounding force that attracts all objects towards each other.

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The grounding force that attracts all objects towards each other.

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The tendency of an object to resist a change in motion

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The tendency of an object to resist a change in motion

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inertia keeps the moon and Earth in orbit

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inertia keeps the moon and Earth in orbit

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Unit Summary:  In this unit, you will gain an understanding of why Earth can be described as a system with four main parts, and you will explore some of Earth’s properties that make it suitable for life. You will study Earth’s atmosphere and learn how temperatures on Earth are just right for various life forms. By studying Earth’s rotation and its revolution, you will learn what causes day and night and why there are seasonal cycles on the “blue planet.” By the end of the unit, you will also be able to describe characteristics of Earth’s moon, list the phases of the moon, and explain why the moon goes through phases. This unit will give you an introductory look at Earth and its place in the solar system, and it will prepare you for upcoming units in astronomy and space science.

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Unit Summary:  In this unit, you will gain an understanding of why Earth can be described as a system with four main parts, and you will explore some of Earth’s properties that make it suitable for life. You will study Earth’s atmosphere and learn how temperatures on Earth are just right for various life forms. By studying Earth’s rotation and its revolution, you will learn what causes day and night and why there are seasonal cycles on the “blue planet.” By the end of the unit, you will also be able to describe characteristics of Earth’s moon, list the phases of the moon, and explain why the moon goes through phases. This unit will give you an introductory look at Earth and its place in the solar system, and it will prepare you for upcoming units in astronomy and space science.

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Identify and describe the four main components of the Earth system and explain the properties of Earth that support life

Define rotation and revolution and explain why day and night and seasons occur

Identify what determines the strength of the force of gravity between two objects and describe what factors keep the moon and Earth in orbit

Describe the features and characteristics of the moon and explain why the moon has phases and the effect the sun and the moon have on tides

Define the term eclipse and explain when solar and lunar eclipses occur

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An orbit is the path one object in space takes around another.

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Day and Night occur because Earth rotates.  One Day is roughly 24 hours.  It takes Earth one day to turn once on its axis

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Day and Night occur because Earth rotates.  One Day is roughly 24 hours.  It takes Earth one day to turn once on its axis

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Axis = Earth's rotation is the way it spins on its axis

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Axis = Earth's rotation is the way it spins on its axis

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Rotation = Earth spinning on its axis is why we have day and night

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Rotation = Earth spinning on its axis is why we have day and night

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Revolution = Earth's movement around the sun... It takes Earth one year or 365 days to revolve around the sun.

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Revolution = Earth's movement around the sun... It takes Earth one year or 365 days to revolve around the sun.

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Tilt = Earth's tilt like in the picture is what causes the sun to shine on different latitudes of the Earth and the latitude tells us how far north or south a place is from the equator.  This affects the length of our days.

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Tilt = Earth's tilt like in the picture is what causes the sun to shine on different latitudes of the Earth and the latitude tells us how far north or south a place is from the equator.  This affects the length of our days.

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Equator = is an imaginary line around the middle of a planet or other celestial body.  It is halfway between the North Pole and the South Pole at 0 degrees latitude.  This divides our planet into 2 hemispheres.

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Equator = is an imaginary line around the middle of a planet or other celestial body.  It is halfway between the North Pole and the South Pole at 0 degrees latitude.  This divides our planet into 2 hemispheres.

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Hemispheres = This is an imaginary division of Earth in 2 halves.

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Hemispheres = This is an imaginary division of Earth in 2 halves.

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Seasons = four different times during the year with different types of weather.  These are caused by the Earth's orbit around the sun, its rotation on its axis, and its tilt.

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Seasons = four different times during the year with different types of weather.  These are caused by the Earth's orbit around the sun, its rotation on its axis, and its tilt.

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Equinox = This is when the sun passes directly over the equator.  There are two equinoxes each year.  On these days, the nights are equal in length North and South.  12 hours for day and 12 hours for night

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Equinox = This is when the sun passes directly over the equator.  There are two equinoxes each year.  On these days, the nights are equal in length North and South.  12 hours for day and 12 hours for night

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Winter Solstice = The time when the sun has the biggest distance to the Tropic of Cancer.

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Winter Solstice = The time when the sun has the biggest distance to the Tropic of Cancer.

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Summer solstice = Sometimes called "midsummer", occurs when one of the Earth's poles has its maximum tilt toward the sun.  This happens twice yearly in both the North and South hemispheres.

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Summer solstice = Sometimes called "midsummer", occurs when one of the Earth's poles has its maximum tilt toward the sun.  This happens twice yearly in both the North and South hemispheres.

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crater = large, round pits on the surface of the moon

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crater = large, round pits on the surface of the moon

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maria = dark, flat areas on the surface of the moon 

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maria = dark, flat areas on the surface of the moon 

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meteoroid = a small rocky body moving in the solar system

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meteoroid = a small rocky body moving in the solar system

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phases = there are 8 different phases of the moon that can be viewed from Earth

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phases = there are 8 different phases of the moon that can be viewed from Earth

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lunar eclipse =  When an object in space comes between the sun and a third object, a shadow is cast on that object, and an eclipse occurs. occurs when the Earth is directly between the moon and the sun, causing the Earth to block sunlight from reaching the moon .

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lunar eclipse =  When an object in space comes between the sun and a third object, a shadow is cast on that object, and an eclipse occurs. occurs when the Earth is directly between the moon and the sun, causing the Earth to block sunlight from reaching the moon .

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solar eclipse = occurs when the moon passes directly between the Earth and the sun, causing the moon to cast a shadow on part of Earth. 

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solar eclipse = occurs when the moon passes directly between the Earth and the sun, causing the moon to cast a shadow on part of Earth. 

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Umbra = The umbra is the darkest part of the shadow cast by the intervening body. 

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Umbra = The umbra is the darkest part of the shadow cast by the intervening body. 

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penumbra = the region where only a partial shadow is cast.

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penumbra = the region where only a partial shadow is cast.

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high tide =   when the tide/water is at its greatest elevation.

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high tide =   when the tide/water is at its greatest elevation.

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low tide = When the tide/water is at its lowest elevation.

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low tide = When the tide/water is at its lowest elevation.

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A tide is the periodic rising and falling of Earth's ocean surface caused mainly by the gravitational pull of the Moon acting on the oceans. Tides cause changes in the depth of marine and estuarine (river mouth) waters. Tides also make oscillating currents known as tidal streams (~'rip tides'). This means that being able to predict the tide is important for coastal navigation. The strip of seashore that is under water at high tide and exposed at low tide, called the intertidal zone, is an important ecological product of ocean tides.

The height of tides varies somewhat with the phases of the Moon. At New Moon and Full Moon, tides are higher because the Sun's tidal force adds to the Moon's. This is called "spring tide".

Two tides a day

In most places, there are two tides a day. They each have a high point (the high tide) and a low point (the low tide). We speak of a "flood tide" coming in towards high tide, and an "ebb tide" going out towards low tide.

The period of the tide is about 12 hours and 25.2 minutes, exactly half a tidal lunar day.

The Moon orbits the Earth in the same direction as the Earth rotates on its axis, so it takes slightly more than a day-about 24 hours and 50 minutes-for the Moon to return to the same location in the sky. During this time, it has passed overhead once and underfoot once, so in many places the period of strongest tidal forcing is the above-mentioned, about 12 hours and 25 minutes. This is analogous to the minute hand on a watch crossing the hour hand at 12:00 and then again at about 1:05½ (not at 1:00).

Because a gravitational field weakens with distance, the Moon's gravity exerts a slightly stronger pulling force on the side of the Earth facing the Moon, and a slightly weaker force on the opposite side. The Moon thus tends to "stretch" the Earth slightly along the line connecting the two bodies. The solid Earth deforms a bit, but ocean water, being fluid, is free to move much more in response to the tidal force, particularly horizontally. As the Earth rotates, the magnitude and direction of the tidal force at any particular point on the Earth's surface change constantly; although the ocean never reaches equilibrium-there is never time for the fluid to "catch up" to the state it would eventually reach if the tidal force were constant-the changing tidal force nonetheless causes rhythmic changes in sea surface height.

Other things, such as atmospheric pressure and the Sun's gravity, also affect the tides, but in most places those things do much less than the Moon's gravity does.

Related pages

Tide predictions

Images for kids

M 2 tidal constituent. Red is most extreme (highest highs, lowest lows), with blues being least extreme. White cotidal lines converge in blue areas indicating little or no tide. The curved arcs around these convergent areas are amphidromic points. They show the direction of the tides, each indicating a synchronized 6-hour period. Tidal ranges generally increase with increasing distance from amphidromic points. Tide waves move around these points, generally counterclockwise in the N. Hemisphere and clockwise in the S. Hemisphere

Brouscon's Almanach of 1546: Compass bearings of high waters in the Bay of Biscay (left) and the coast from Brittany to Dover (right).

In Spanish: Marea para niños

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neap tide = a tide just after the first or third quarter of the moon when there is the least difference  between high and low water.

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neap tide = a tide just after the first or third quarter of the moon when there is the least difference  between high and low water.

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spring tide = a tide just after a new or full moon, when there is the greatest =difference between high  and low water.

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spring tide = a tide just after a new or full moon, when there is the greatest =difference between high  and low water.

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tidal bulge = the distortion of water and earth which is a result of the combined gravitational effects of moon and sun.

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tidal bulge = the distortion of water and earth which is a result of the combined gravitational effects of moon and sun.

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Gravity, or gravitation, is one of the fundamental forces of the universe. In this article, we discuss it in three parts:

1. Everyday sense: the force which causes objects to fall onto the ground.

2. Newton's laws: how gravity keeps the Solar System together.

3. Einstein's theory of general relativity: the role of gravity in the universe.

Some physicists think gravity is caused by gravitons, but they are still unsure.

Everyday gravity

Weight vs mass

In everyday talk, we say things fall because the Earth's gravity pulls on them. We talk as if our weight was a "given". Actually, weight changes when the pull of gravity changes. The Moon is much smaller and the pull of gravity on the Moon is about 1/6th that of Earth. So any object on the Moon weighs 1/6th of its weight on Earth. What does not change is the amount of matter in an object. That is called its mass. On Earth, mass and weight are the same for practical purposes. The trip to the Moon shows they are not really the same.

From this we learn two things.

1. The weight of an object is variable; its mass is constant.

2. The pull of gravity varies according to the mass of an object. The Earth pulls more strongly than the Moon. A person also exerts a gravitational pull, but it is so tiny it can be ignored for all practical purposes.

The Earth has mass. Every particle of matter has mass. So the Earth pulls on every object and person and they pull on the Earth. Gravity pulls on the mass and gives it weight.

Acceleration due to gravity

The acceleration gained by an object because of gravitational force is called its acceleration due to gravity.

The acceleration due to gravity at the surface of Earth is represented as g.

Why heavier objects do not fall faster

Isaac Newton deduced that the resultant force equals mass times acceleration. The bigger the mass of the falling object, the greater the force of gravitational attraction pulling it towards Earth. However, the bigger mass cancels out the greater force of attraction, so the acceleration is the same.

A common experiment to see this is to drop a feather and a bowling ball from the same height. To see the effect of gravity you need to remove all the air from the room so you don't get any air resistance (a vacuum). Both the feather and the bowling ball will reach the bottom at the same time, despite the feather being lighter and the bowling ball being heavier.

Gravity vs gravitation

These words mean almost the same thing in everyday use. Sometimes scientists use "gravity" for the force that pulls objects towards each other, and "gravitation" for the theory about the attraction.

History of gravitational theory

In the late 16th century, Galileo did a famous experiment about gravity where he dropped balls from the Tower of Pisa. He later rolled balls down inclines. With these experiments, Galileo showed that gravitation accelerates all objects at the same rate regardless of weight.

The man who really worked it all out was Johannes Kepler, who, after "900 pages of calculations and many false starts and dead-end ideas", finally got these three laws:

1. Kepler's elliptical orbit law: The planets orbit the sun in elliptical orbits with the sun at one focus.

2. Kepler's equal-area law: The line connecting a planet to the sun sweeps out equal areas in equal amounts of time.

3. Kepler's law of periods: The time required for a planet to orbit the sun, called its orbital period, is proportional to the long axis of the ellipse raised to the 3/2 power. The constant of proportionality is the same for all the planets.

In 1687, English mathematician Isaac Newton wrote the . In this book, he wrote about the inverse-square law of gravitation. Newton said that the closer two objects are to each other, the more gravity will affect them. His theory about gravitation was used to predict the existence of the planet Neptune based on changes in the orbit of Uranus.

Newton's theory was later used to predict the existence of another planet closer to the Sun than Mercury. When this was done, it was learned that his theory was not entirely correct. These mistakes in his theory were corrected by Albert Einstein's theory of General Relativity. Newton's theory is still commonly used for many things because it is much more simple to work with than the theory of General Relativity and is usually accurate enough for many uses.

Dynamic equilibrium

Why does the Earth not fall into the Sun? The answer is simple but very important. It is because the Earth moving round the Sun is in a dynamic equilibrium. The speed of the Earth's movement creates a centrifugal force which balances the gravitational force between the Sun and the Earth. Why does the Earth continue spinning? Because there is no force to stop it.

Newton's first law: "If a body is at rest it remains at rest or if it is in motion it moves at the same speed until it is acted on by an external force".

There is a kind of analogy between centrifugal force and gravitational force, which led to the "equivalence principle" of general relativity.

Weightlessness

In free fall a thing's motion balances out the pull of gravity on it. This includes being in orbit.

General relativity

The special theory of relativity describes systems where gravity is not an issue; by contrast, gravity is the central issue of the general theory of relativity.

In general relativity there is no gravitational force deflecting objects from their natural, straight paths. Instead, gravity is seen as changes in the properties of space and time. In turn, this changes the straightest-possible paths that objects will naturally follow. The curvature is, in turn, caused by the energy-momentum of matter. Spacetime tells matter how to move; matter tells spacetime how to curve.

For weak gravitational fields and slow speeds relative to the speed of light, the theory's predictions converge on those of Newton's law of universal gravitation. Newton's equations are used to plan journeys in our Solar System.

General relativity has a number of physical consequences.

Gravitational time dilation and frequency shift

Gravity influences the passage of time. Light sent down into a gravity well is blueshifted, whereas light sent in the opposite direction (i.e., climbing out of the gravity well) is redshifted; collectively, these two effects are known as the gravitational frequency shift.

More generally, processes close to a massive body run more slowly when compared with processes taking place farther away; this effect is known as gravitational time dilation.

Light deflection and gravitational time delay

General relativity predicts that the path of light is bent in a gravitational field; light passing a massive body is deflected towards that body. This effect has been confirmed by observing the light of stars or distant quasars being deflected as it passes the Sun.

Closely related to light deflection is the gravitational time delay (or Shapiro delay), the phenomenon that light signals take longer to move through a gravitational field than they would in the absence of that field. There have been numerous successful tests of this prediction.

A parameter called γ encodes the influence of gravity on the geometry of space.

Gravitational waves

Gravitational waves are ripples in the curvature of spacetime. They move as a wave, travelling outward from the source. Einstein predicted them in 1915 on the basis of his theory of general relativity. In theory, gravitational waves transport energy as gravitational radiation. Sources of detectable gravitational waves might include binary star systems composed of white dwarfs, neutron stars, or black holes. In general relativity, gravitational waves cannot travel faster than the speed of light.

Although gravitational radiation has not been directly detected, there is indirect evidence for its existence. The 1993 Nobel Prize in Physics was awarded for measurements of the Hulse-Taylor binary star system. These measurements suggest gravitational waves are more than mathematical peculiarities. Various gravitational wave detectors exist. However, they have not yet detected the phenomena.

Related pages

Images for kids

An initially-stationary object which is allowed to fall freely under gravity drops a distance which is proportional to the square of the elapsed time. This image spans half a second and was captured at 20 flashes per second.

Gravity acts on stars that form our Milky Way.

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Gravity, or gravitation, is one of the fundamental forces of the universe. In this article, we discuss it in three parts: Everyday sense: the force which causes objects to fall onto the ground. Newton's laws: how gravity keeps the Solar System together. Einstein's theory of general relativity: the role of gravity in the universe.