What is the continental shelf?

The shallow underwater plateaus of land surrounding the continents form the continental shelf. They slope gently down to a depth of about 180 m, after which they slope more sharply...

What causes the tides?

Tides are caused by the gravity of the Moon. As the Earth spins round, the water in the oceans is 'pulled' towards the Moon slightly, making a bulge. There is a corresponding bulge...

What are the northern lights?

The northern lights are streaks and sheets of pale, flickering, colored lights that are sometimes seen in the night sky in far northern regions. Their proper name is the aurora...

Why do we have day and night?

As the Earth spins on its axis, the Sun always shines on one side giving us daylight. It is night on the shaded side. As the Earth continues to turn, the shaded side moves into...

What is inside the Earth?

The Earth is not solid rock all the way through. It has an inner core of solid rock, which is mostly iron. The temperature here is probably around 4,500°C. Beyond the inner core...

How do you breathe in space?

You cannot breathe in the vacuum of space because there is no air. Oxygen is the gas we need to stay alive, and it forms an important part of the air we breathe. AII space missions...

Has any spacecraft ever left the Solar System?

Pioneer 10 is the first man-made object to leave the Solar System. This probe was launched towards Jupiter in 1972 and by 1983 it had reached deep space. Pioneer 10 carried messages...

How do satellites stay up?

The speed with which a satellite is launched helps to keep it in orbit. To stay up above the Earth, a satellite must be launched at a speed of about 8 km per second. If the orbit...

One giant leap!

The Apollo project was the United States' plan to get humans on the Moon during the I960s. It used the world's most powerful rocket, Saturn V, to launch the three-man Apollo spacecraft....

Rocket power!

AII space flight depends on the use of rockets that burn huge amounts of fuel. They burn high-energy fuel in a chamber which directs the burning gases through a nozzle. As the gases...

What do space satellites do?

Space satellites have revolutionized Communications, making possible everyday developments such as mobile phones and television. Communications satellites receive signals beamed...

What is the space shuttle?

The space shuttle is the first re-usable spacecraft. It was developed to provide a re-usable, and therefore cheaper, vehicle for launching satellites and for other work in space. The...

What does the surface of the Moon look like?

The Moon's surface is covered with a thick layer of gravel-like rock and dust. This material was created by the impact of millions of meteorites. The Moon also has mountain ranges,...

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....

How far away is the Moon?

The distance of the Moon away from the Earth was settled once and for all after the Apollo astronauts left a small reflector on the Moon's surface. Lasers were directed at this...

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 1/2 days, which is also the time it takes...

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...

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...

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...

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...

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...

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...

What is a comet?

Comets are often described as 'dirty snowballs’. The solid centre, or nucleus, of a comet consists mostly office mixed with sooty material. The nucleus is quite small, and is usually...

What are shooting stars?

Shooting stars, or meteors, are streaks of light that cross the night sky, although they can only be seen for one or two seconds. They are caused when a solid piece of rock called a...