Educational Stories

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Solar Eclipse:

Sometimes the Moon moves between the Sun and the Earth so the three are in a straight line. The Moon blocks the Sun's light and part of the Earth is in the Moon's shadow. This is a solar eclipse.

Discover what happens in a solar eclipse.

What you need about Solar Eclipse...

globe of the Earth

ball with string attached (Moon)

torch (Sun)

Ploce the Eorth, Moon and Sun in line so that the Moon is in the middle.

Turn on the Sun and observe the shadow that falls on a small part of Eorth.

Rotote the Eorth so that the eclipse occurs where you live.

Day and Night:

Earth's rotation on its axis causes day and night.

As Earth spins, sunlight only falls on one-half of the planet. This means it is daytime on that side of Earth. On the other side, it is night. This way we have Day and Night.

The apparent movement of the Sun across the sky is actually due to the rotation of our Earth. The Sun always appears to rise in the east and set in the west regardless of where you are on Earth.

When the Sun rises, that part of the Earth is turning to face the Sun. When the Sun sets, that part of the Earth is turning away from the Sun. The Sun itself doesn't actually rise or set. Each planet spins around or rotates on its axis.

Earth spins around at a speed of 1 600 km/h. Earth takes almost 24 hours to complete one rotation around the Sun. Because each rotation takes slightly less than 24 hours the calendar needed adjusting. Leap years add an extra day, the 29th February, to the calendar every four years so that the calendar aligns with Earth's motion around the Sun.

Moon Phases :

We see the Moon because sunlight is reflected from its surface. As the Moon orbits Earth and as Earth orbits the Sun, we see different amounts of the Moon's sunlit face. These are known as the phases of the Moon.

New Moon : The Moon in between Earth and The Sun and The Moon’s unlit side is facing Earth.

Waxing Moon : Less than one-half of the Moon is lit by direct sunlight.

First Quarter : One-half of the Moon is lit by direct sunlight.

Waxing Gibbous : More than one-half of the Moon is lit by direct sunlight.

Full Moon : Two weeks after the New Moon, the Moon os halfway through its orbit. The Moon’s sunlit side is looking Earth.

Waning Gibbous : More than one-half of the Moon is lit by direct sunlight.

Last Quarter : One-half of the Moon is lit by direct sunlight.

Waning Crescent : Less than one-half of the Moon is lit by direct sunlight.

Near-Earth-Objects:

Near-Earth-Objects (NEOs) are small objects in the solar system. They have struck Earth in the past and will definitely hit again, but are we in danger of Near-Earth-Objects?

The Earth has been hit by asteroids, comets and meteorites in the past. Scientists believe that when a large asteroid collided with Central America 65 million years ago, the dinosaurs became extinct. The collision threw up water and rock which hid the Sun and covered the Earth in darkness for months. Dinosaurs could not survive in the cooler climate.

Of the Near-Earth-Objects, Most meteors are tiny and burn up in Earth's atmosphere. Even the ones that do get through and land as meteorites are mostly very small. The Earth's atmosphere protects us from all objects up to about 40 metres across. Asteroids pose a much bigger threat to Earth as they tend to be much larger objects.

If an asteroid with a diameter of more than two kilometres hit the Earth, it would cause a catastrophic planetary event. Many people would die as a result of the impact and of the Earth entering a long cold winter where most crops die. The good news is that an asteroid of this size only collides with Earth about once every 100 million years. The Spaceguard survey scans the skies looking for any dangerous NEOs. As yet, none that are on a collision course with Earth, have been discovered.

When a bigger object does head our way, we should have the advance warning and technology to deal with it.

Asteroids and Meteoroids and Comets

Asteroids are pieces of rock and iron that orbit the Sun.

Meteoroids are smaller bits of material that fly through space.

Comets orbit the Sun and are made of ice, dust and rock.

Asteroids :

Asteroids are known as minor planets although they can range in size from a few metres across to the largest – Ceres - which is almost 1000 km wide. Many asteroids are found orbiting in a belt between Mars and Jupiter.

Meteoroids :

Meteoroids travel at great speed. When they enter Eorth's atmosphere, they bum up due to friction with the air. These streaks of light ore called meteors or shooting stars. If meteors don't burn up completely, due to their large size, they hit Earth's surface. These are called meteorites. The Barrington Crater in Arizona, USA, was formed when a 30-50 metre iron meteorite hit Earth about 50000 years ogo. It is one of about 120 impoct craters on Earth.

Comets :

There are billions of comets orbiting the Sun. A comet doesn't have a tail for most of its orbit. As a comet moves closer to the Sun, it begins to warm up. Gas and dust from the nucleus or solid icy centre of the comet begin to form a cloud or a coma around the nucleus. The Sun and its solar wind blow the coma into two tails - one of gas and one of dust. As the comet moves away from the Sun, the tails shrink.

Halley's comet is the best known periodic comet with the first recorded sighting being in China in 240 BC. It returns to Earth every 75-76 years. Its next visit to the inner solar system will be the summer of 2061.

AMAZING FACTS about Our Solar System :

A comet's tail can be millions of kilometres long.

Over 9 000 asteroids hove been located and named.

An asteroid, colled Ido, has its own moon called Dactyl.

Halley's comet lost visited Earth in 1986.

Uranus and Neptune

The two furthest planets from the Sun are Uranus and Neptune. Uranus and Neptune are both gas planets.

Blue-Green Methane

Both Uranus and Neptune have atmospheres of hydrogen, helium and methane. The methane gives these planets a blue-green colour. Below the atmosphere, both planets have liquid layers of water ice, methane and ammonia around small, rocky cores.

Uranus:

Uranus, its rings and moons all orbit the Sun, tipped on their side. This may have been caused by a collision with another huge object. The result is that each pole on Uranus receives 42 Earth years of sunlight followed by 42 years of darkness.

Neptune:

Neptune, like Uranus, has rings and moons. It has a stormy atmosphere and has the fastest recorded winds in the solar system. These storms may be caused by heat generated within Neptune.

Jupiter and Saturn

Jupiter is the largest planet in the solar system and has the fastest rotation. Saturn is the second-largest planet surrounded by rings of ice-covered rock. Both are gas giants.

Jupiter :

If oil the other planets were combined into one, its moss would be less than half of Jupiter's. It is 1300 times larger than Earth.

Jupiter completes its rotation in less than ten hours. This speed results in strong winds and huge cloud bands. Strong storms develop when these bands of clouds meet. One hurricane known as the Great Red Spot has existed for over 300 years.

Saturn :

Like Jupiter, Saturn is made of hydrogen and helium gas. Saturn's rotation is almost as fast as Jupiter's. Saturn also has very strong winds reaching speeds that are 11 times faster than a hurricane on Earth. There are thousands of rings surrounding Saturn. Each ring contains pieces of ice and rock travelling in orbit around Saturn. The rings closer to the planet seem to hold larger pieces while the outer rings contain finer materials. Both Jupiter and Saturn have many satellites some discovered only very recently. Jupiter seems to have the most moons of any planet in our solar system — at least 62. Saturn has more than 30.

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Mars

Mars is a red planet with some similar features to Earth. It is still not known whether Mars has ever supported life.

Similar Features :

The soil on Mars contains iron oxide which gives the planet its red colour. Iron oxide is a mineral also found in Earth's soil. There is evidence that water once flowed on the Martian surface. There are valleys that have been eroded by water and dry riverbeds. Mars has icecaps at its north and south poles like Earth. The length of a Martian day is about 40 minutes longer than a day on Earth. Mars also has a similar tilt on its axis to Earth so it has the same pattern of seasons.

Volcanoes occur on Mars. In fact, Olympus Mons is the largest volcano in the solar system. It is 25 kilometres high and 600 kilometres wide.

Cold With No Oxygen :

There are significant differences between the atmospheres on Mars and on Earth. Mars has a very thin atmosphere of carbon dioxide which means that we could not survive on Mars. Mars is a very cold planet. The temperature falls to as low as -120 degrees with a maximum of around 0 degrees Celsius. Winds on Mars can cause huge dust storms which cover the whole planet.

AMAZING FACTS about Our Solar System :

The inner solar system is separated from the outer by the asteroid belt.

The solar system is port of the Milky Way galaxy which is a barred-spiral galaxy.

There were 9 planets in the Solar System until 2006 when the International Astronomical Union decided that Pluto could no longer be considered a plonet due to its size being smaller than our moon.

If all the planets were joined together, the Sun would still be more than 700 times bigger. It contains over 99% of the solar system's mass.

It takes two million years for gamma rays produced in the core of the Sun to reach its surface.

The Sun is the largest object the solar system. It is about 332 950 times more mossive than Earth.

The relationship between the Sun and the Earth drives the seasons, currents in the ocean, weather and climate.

The Sun has been burning for about five billion years and will bum for another five billion.

If you stood on Venus, the atmospheric pressure would be the same as if you were 900 metres underneath an ocean on Earth.

Much of the surface of Venus, including craters, has been covered in lava from previous eruptions.

Mercury and Venus are the only two planets in our solar system that don't have moons.

Mercury has the greatest variation in surface temperature of any planet in the solar system — can be over 600 degrees Celsius.

Because there is no wind or rain on the Moon, any footprints left by the astronauts should remain for millions of years.

It is thought that Earth was hit by a lorge object and the debris that was ejected into space joined together to form the Moon.

The official Latin name for planet Earth is Terra. It is named after the Roman goddess of fertility and growth - Terra Mater.

The Moon is the only other planet or satellite in the solar system that humans hove set foot upon.

The length of each Martian season is almost twice as long as a season on Earth.

Mars has the least hostile environment of all the other planets in the solar system.

The surface area of Mars is approximately equal to that of Earth's dry land as Mars does not have any oceans.

Mars has two small moons. They have uneven shapes and may originally have been asteroids.

After the Sun, the Moon and Venus, Jupiter is usually the fourth brightest object in the sky.

Saturn is almost exactly the same as Jupiter, just smaller. The only striking difference is the rings around Saturn.

Saturn's rings are thought to be particles of an old moon which was smashed to pieces in a collision million of years ago.

Jupiter is made of hydrogen and helium gases which also make up the Sun. If Jupiter had been any bigger, it could have become a star.

It takes 84 Earth years for Uranus to complete one full orbit around the Sun.

The Kuiper Belt contains many comets, asteroids and other small bodies made largely of ice.

As its orbit is so for from the sun, Neptune receives very little heat - in fact the uppermost regions of its atmosphere are -218 degrees Celsius.

Mercury and Venus

Mercury and Venus are the two planets closest to the Sun. The conditions on each planet are very different.

Rocky Planets :

Both Mercury and Venus are made of solid rock, but they look completely different. About 60% of Mercury's surface is covered in craters caused by meteorites crashing into the planet. This makes it look very similar to Eorth's moon.

Venus has many volcanoes. There is a major difference between the atmospheres on the two planets. Mercury has almost no atmosphere. Venus has a thick atmosphere of corbon dioxide covered by spinning clouds of sulphuric acid.

Temperature :

Although Mercury is the closest planet to the Sun, Venus is actually the hotter planet. Mercury's temperature reaches 427 degrees Celsius during the day. Since there is no atmosphere to trap heat near the surface of the planet, the temperature falls to -180 degrees Celsius at night.

On Venus, any heat that finds its way through the thick atmosphere is trapped near the surface of the planet, producing a greenhouse effect. The temperature reaches 480 degrees Celsius. This heat also means water cannot exist as a liquid on either Mercury or Venus.