Category Science

How old is the Earth?

Earth is millions and millions of years old. In fact, our planet is four-thousand-six-hundred-million years old. When the Earth’s age (4.6 billion years) is written as a number, it looks like this: 4,600,000,000. It’s hard for us to imagine anything so old.

Has there always been life on the Earth?

Nothing at all lived on the Earth for the first billion (1,000 million) years of the planet’s existence. The conditions were not right for life. There were no plants or animals of any kind. Earth was a dangerous place where life could not survive.

Amazing! Some of Earth’s oldest known rocks are found in Scotland. They are about 3.5 billion years old.

Has the Earth always looked the same?

These maps show how Earth’s land and sea looked in the past. To fit everything on them, Earth has been drawn as an oval. For a long time, all land was joined together in one giant mass. Over millions of years it broke up into smaller pieces. They turned into today’s continents.

Is it true? The continents are still moving.

Yes. The continents move about 4 centimetres each year – the length of your little finger. Millions of years in the future, Earth will look very different from today.

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What’s better than a powerful telescope?

Seeing for yourself in close-up – but it’s too dangerous and expensive to send astronomers deep into space. That’s why space probes are such important tools. Space probes are fitted with cameras. They beam back close-up photos of faraway planets and comets.

Amazing! Chandra is a billion times more powerful than the first X-ray telescope. If telescopes keep improving at this rate, we’ll be able to see the farthest edges of the Universe in 30 years’ time!

Is it true? A probe found a watery world.

Yes. The Voyager 2 probe photographed what might be water on Jupiter’s moon, Europa. If there is life out there, probes will probably find it first.

Could we build an observatory on the Moon?

The dark side of the Moon would be a perfect site. Always pointing away from the Earth, it is shielded from man-made X-rays. But building there would be very expensive.

Could we build Very Large Arrays in space?

Scientists are already testing a cluster of satellites that fly in perfect formation, using laser beams. The same technology will be used to create a string of small satellite telescopes, making one huge ‘eye’ in space.

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Who made the first radio telescope?

Radio telescopes are like giant satellite dishes that pick up invisible radio waves and similar waves, instead of light rays. Unlike light, radio waves can travel through cloud, so radio telescopes can be built just about anywhere! An American called Grote Reber made the first one in the 1930s.

Amazing! A telescope can be 8,000 km long. The Very Long Baseline Array (VLBA) stretches across the USA. It has ten different dishes and produces the best-quality radio images of space from Earth yet!

Which are the most powerful radio telescopes?

The ones that are made up of several different radio dishes, such as the Very Large Array (VLA) in New Mexico, USA. The VLA has 27 dishes, each 25 metres across. Scientists compare the findings from all 27 dishes to get super-accurate results.

Where is the biggest radio telescope?

The world’s biggest single-dish radio telescope was built in Puerto Rico in the Caribbean about 40 years ago. It is 300 metres across – so it would take you more than ten minutes to walk around the edge of it.

Is it true? Only ten astronomers are allowed to use the VLA.

No. It is used by over 500 astronomers a year. Some study our near-neighbours in the Solar System, while others peer way beyond our galaxy to others in deepest space.

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How deep is space?

Early astronomers thought that all the stars were the same distance from us, forming a simple shell around the Earth. Now we know that some stars are relatively close to us, and others are trillions of kilometres away.

Is it true? We measure how far the stars are in kilometres.

No. They’re so far away, that we use light years instead. A light year is how far light travels in one year – 9,461 billion km!

Are there candles in space?

Not really. But we can see how far away a galaxy is by the brightness of a special type of star, called a ‘standard candle’. The further away the galaxy, the dimmer the candle.

Amazing! Galaxies move so quickly they are different colours. The light waves from them change, just as a fire engine’s siren sounds lower after it zooms past. We use the colour to measure the galaxies’ speed.

How do you measure the distance to a star?

Watch the tip of your finger as you move it towards to your nose. The closer it gets, the more cross-eyed you become! Astronomers can tell the distance to a star by measuring how ‘cross-eyed’ a pair of telescopes has to be to see it.

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Where do astronomers put their telescopes?

Observatories are buildings where astronomers go to look at the sky. They house the most powerful telescopes on Earth. The telescopes are usually kept in a room with a dome-shaped roof. Observatories have other instruments too, such as very precise clocks, to help keep accurate time and records.

Where’s the best place to build an observatory?

Where you’ll get the clearest view! Most are built away from city lights. Mountain-tops are best of all, because they poke above any clouds that might spoil the view.

How can a telescope see through the roof?

It doesn’t have to – an observatory’s domed roof is specially designed to slide open at night, so that the picture through the telescope isn’t distorted (blurred) by looking through a window. The telescope can be pointed at any place in the sky.

Amazing! The Ancient Babylonians used observatories. They did their star-gazing from stepped towers called ziggurats.

Is it true? The Greenwich Observatory houses the most telescopes.

No. The Kitt Peak National Observatory in Arizona, USA has the most optical telescopes. One of them, the Mayall Telescope, is 4 m across!

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Who said that planets go round the Sun?

Nicolaus Copernicus explained this idea in a book in 1543. The problem was, the Church stated that God had put the Earth at the centre of the Universe. You could be put to death for saying that the Earth went round the Sun.

Who was put on trial for star-gazing?

Few scientists were brave enough to say that they agreed with Copernicus’s findings that the Earth went round the Sun. The Italian astronomer Galileo was – and was put on trial for his ideas in 1634.

Is it true? The Church accepted that Galileo was right in the end.

Yes. The Church eventually agreed that the Earth and other planets travelled round the Sun. But they didn’t do this until 1992 – 350 years after Galileo’s death!

Who first used a telescope for astronomy?

Galileo started making telescopes in 1609, not long after Lippershey made his. Galileo was the first person to realize how useful a telescope would be for looking at the night sky. Because he could see more clearly, he made lots of important new finds, such as discovering four of Jupiter’s moons.

Amazing! Copernicus explained the seasons. By showing that the Earth goes round the Sun and also spins at the same time, Copernicus explained why some times of the year are warmer than others.

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