Category Science

What is the Moon made of?

The Moon is a rocky satellite, and is made of similar material to the Earth. It has an outer layer, or mantle, of rock, and a core that is probably made up mostly of iron. Unlike the Earth’s liquid mantle, the interior of the Moon is cool and solid. There is little or no volcanic activity on the Moon. However, while it was cooling early in its life, floods or streams of lava ran out across the Moon’s surface. 

Dead planet!

Living things need air and water to stay alive, and neither of these is available on the Moon. The atmosphere of the Moon is a higher vacuum than can be created in most scientific laboratories. The Moon also suffers extreme temperature swings between the lunar day and night. Lunar conditions have been re-created in laboratories on the Earth, but no form of terrestrial life has been able to survive them. There is some water on the Moon’s surface, in the form of frost that can be found in shadowed craters near the Moon’s poles. 

What is a lunar month?

For thousands of years people have used the Moon to measure the passing of time and the seasons. The Moon revolves around its own axis every 29  days, which is also the time it takes to complete one orbit around the Earth. This period of time is known as a lunar month. Our calendar has been devised to follow this astronomical pattern fairly closely. It has to be adjusted slightly to round up the number of days in each month to a more convenient figure. The sidereal month, of 27.32 days, measures the time it takes for the stars to return to an identical position in the sky.

Wobbling Moon

We always see the same side of the Moon as it rotates around the Earth. However, it wobbles slightly as it orbits the Earth, giving us a glimpse of some of the features around the edges of its hidden side. Because of this wobble, we can actually see about 59 percent of the Moon’s surface from the Earth. 

Continue reading “Our Moon”

Why does the Moon shine?

The Moon is by far the brightest object in the night sky, but it has no light of its own. Moonlight is simply the reflected light of the Sun. Parts of the Moon that are not in sunlight are invisible against the deep blackness of space. Although the Moon appears bright and silvery, only a small proportion of the light that falls on it from the Sun is reflected back towards us. This is because the Moon’s surface is grey and rocky, and does not reflect light well. 

Why does the Moon seem to change shape each month?

The appearance of the Moon alters, depending on the position of the Sun in relation to the Moon. The Sun lights up only one side of the Moon. As the Moon orbits the Earth, we see this lit-up area from different angles. When the Sun is almost behind the Earth, it lights up the whole of the Moon; this is called a Full Moon. When the Sun is off to one side, part of the Moon is in deep shadow and all we can see is a thin slice, or crescent, of the Moon’s lit surface. 

What is the Moon?

The Moon is the Earth’s only satellite, and it has been orbiting our planet for at least 4,000 million years. It is a rocky sphere about 3,476 km in diameter, which is about one-quarter the size of the Earth.

Scientists believe that the Moon formed when another planet about the size of Mars collided with the Earth. The collision splashed a huge mass of molten (liquid) rock into space. This molten rock quickly formed into a sphere, and the Moon rapidly cooled into its solid form. The Moon’s surface is heavily pitted by collisions with debris such as asteroids. 

What is a lunar eclipse?

The Earth casts a long shadow into space, and when this shadow passes over the Moon it causes an eclipse.

A lunar eclipse can only happen during a full Moon, when the Sun is directly behind the Earth. It happens only occasionally, because the orbit of the Moon is slightly tilted and so the shadow usually misses it. Lunar eclipses can last for over one hour, but they do not completely black out the shadowed part of the Moon. Some sunlight always filters through, making the shadow look a reddish-brown colour. 

What happens when a meteorite hits the ground?

When a large meteorite hits the ground it can produce a crater. Meteorite craters are rare on the Earth, because the atmosphere slows the meteorite and also usually burns it up. Many ancient meteorite craters have been worn away by water and by weather over thousands of years.

On planets and moons with no atmosphere, huge numbers of meteorites strike with enormous power. Our own Moon is estimated to have 3,000,000 million meteorite craters measuring 1 m or more in diameter. Some of the large geographical features on the Moon and other planets and moons throughout the Solar System are probably the result of strikes by large meteors hitting their surfaces. 

What are meteorites made of?

Meteorites are made of rock or metal. They enter the Earth’s atmosphere at speeds of at least 11 km per second, which makes them glow brightly. Several thousand meteorites enter the Earth’s atmosphere every year, but very few of them reach the ground. The largest known meteorite is made of iron and weighs 66 tonnes. It probably fell to the Earth in prehistoric times in what is now Namibia, southwest Africa.

In general it is hard to find meteorites. Recently, researchers have been locating them on the ice sheets in the Arctic and Antarctic, where they are easier to find. 

Why is Europa especially interesting?

Europa is one of Jupiter’s moons. In 1979 the Voyager spacecraft passed by Europa and found that it had a very smooth surface covered with ice. It has very few craters, which has led astronomers to suspect that there may be liquid water beneath the surface. In theory, there might even be a form of primitive life hidden beneath the ice, where water remains as a liquid.

What is the tail of a comet?

You cannot see the nucleus of a comet with the naked eye, but you can sometimes see its tail. It appears as a smear of light that moves very gradually across the sky. As a comet moves closer to the Sun, the ice and other frozen gases in its nucleus begin to boil off, producing a long tail of gas and dust. The tail always points away from the Sun because light and other forms of radiation from the Sun push against the minute particles that are present within the tail.

What is an asteroid?

Asteroids are small rocky or icy bodies that orbit the Sun. They are sometimes called minor planets. Most asteroids are found in an orbit between Mars and Jupiter, and more than 7,000 of them have been identified.

Asteroids are smaller than any of the planets, and only a few have a diameter of over 30 km. The term asteroid is usually applied to objects larger than 1.6 km in diameter. One asteroid, called Ida, has a tiny moon of its own; this is the smallest known satellite in the Solar System. Asteroids were probably formed at the same time as the planets. 

Space bombardment

Many asteroids have struck the Earth already, and many scientists believe that such an impact resulted in the extinction of the dinosaurs about 65 million years ago. At that time an asteroid or huge meteorite about 10 km in diameter struck the Yucatan region of Mexico. It gouged out a huge crater and hurled so much dust into the Earth’s atmosphere that the world’s climate changed drastically causing the death of the dinosaurs.