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The Doppler effect shows that most distant galaxies are moving away from us.

Physics - Waves from Space (AQA)

Waves from space bring us information about distant stars and galaxies. Discover how radio, infrared and other electromagnetic waves reach Earth and what telescopes can detect.

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Fascinating Fact:

Radio and some infrared pass through air, this is why radio telescopes work from the ground day and night.

In GCSE Science (Physics), you study how electromagnetic waves from space carry information about stars, galaxies and other objects. You learn which wavelengths reach the ground and when telescopes must be placed in space.

Key Terms

Electromagnetic wave: A transverse wave made from changing electric and magnetic fields that can travel through a vacuum.
Radio telescope: A large receiver that collects radio waves from space to build images and measure signals.
Atmospheric window: A range of wavelengths that pass through the atmosphere with little absorption.

Frequently Asked Questions (Click to see answers)

Which electromagnetic waves from space reach the Earth’s surface?

Mainly radio waves, some microwaves, parts of the infrared band and visible light can reach the surface. Many ultraviolet, X-ray and gamma rays are absorbed higher in the atmosphere.

Why do astronomers use radio telescopes as well as optical ones?

Radio telescopes detect objects that are faint or invisible in visible light. They can observe through dust clouds and can collect data day and night in most weather conditions.

Why are some astronomy telescopes put in space?

Space telescopes avoid distortion and absorption by the atmosphere. They can detect wavelengths like ultraviolet and X-rays that do not reach the ground and give sharper images of space.

Try These Related Quizzes

1 .

Which of the following waves can be changed by the Doppler effect?

Light waves

Sound waves

Microwaves

All of the above

Any wave whose source is moving is subject to the Doppler effect

2 .

When the source of a wave moves towards the observer, which of the following is not true?

The frequency of the waves is higher

If the wave is a light wave from a distant galaxy, the light is red-shifted

The wavelength of the waves is less

If the wave is a sound wave, the pitch sounds higher than it would if the source was stationary

Light from a galaxy that is approaching ours would be blue-shifted, not red-shifted

3 .

Galaxies emit (give out) many different types of wave. Which of the following would not be emitted by a galaxy?

Sound

Light

Infrared

X-rays

Sound waves are longitudinal waves and cannot travel through the vacuum of space

4 .

Scientists measuring radio waves from a distant galaxy find the wavelength of the waves they have detected is longer than it should be. What is this called?

Long-shift

Wave-shift

Red-shift

Radio-shift

It doesn't matter what type of electromagnetic radiation you are looking at, if the wavelength has been increased it is still called red-shift

5 .

Scientists discovered that all of the distant galaxies they looked at showed red-shift. What does that tell us about the direction that most galaxies are moving?

They are moving away from us

They are moving towards us

They are neither moving away nor towards us

Red-shift gives no information about how galaxies are moving

Scientists talk about the 'recession of the galaxies'. Recession is an alternative way of saying that the galaxies are moving away from our galaxy

6 .

What information does the red-shift of a galaxy give us?

Its distance and number of stars in the galaxy

Its speed and the number of stars it contains

Its weight and the speed it is moving away

Its distance and the speed of recession

Galaxies often occur in clusters. Our Galaxy is called the 'Milky Way' and is a part of what is called the 'Local Cluster'. Only galaxies in the Local Cluster are blue-shifted and are therefore moving towards us

7 .

What conclusion can be drawn from the fact that nearly all galaxies are moving away from us?

Galaxies repel each other like magnets

The Universe is shaped like a hill and the galaxies are rolling down the hill

Galaxies all have the same electrical charge

The Universe is expanding

American astronomer Edwin Hubble is credited with the discovery that the Universe is expanding. It is possible that a Belgian mathematician, Georges Lemaitre, came to the same conclusion some years before Hubble. Hubble came up with the law named after him. Hubble's Law states that the further away a galaxy is, the faster it is moving

8 .

Which theory about the formation of the Universe is supported by its expansion?

Steady State

Big Bang

Big Crunch

The Oscillating Universe Theory

The term Big Bang was coined by British astronomer Sir Fred Hoyle who actually preferred the Steady State theory

9 .

In 1964, American radio astronomers Arno Penzias and Robert Wilson discovered the cosmic microwave background radiation (CMBR). Why was this an important discovery?

It proved beyond doubt that the Big Bang theory was completely correct

It proved that the Universe will never stop expanding

It provided good evidence to support the Big Bang theory

It completely disproved the Steady State theory

In science, theories are rarely proved beyond any doubt. In time, the Big Bang Theory may even be dropped completely in favour of another that fits the evidence better

10 .

As the Universe gets older, what might happen to the cosmic microwave background radiation?

Its wavelength could increase

It may become stronger

It will suddenly disappear

It will turn into visible light

It is thought that its wavelength will increase as the Universe expands further and cools down even more. The CMBR is currently at a temperature of about 3 K - that's a pretty chilly minus 270^oC

You can find more about this topic by visiting BBC Bitesize - Transverse and longitudinal waves - AQA

Author: Kev Woodward (PGCE, Science & Chemistry Teacher, Quiz Writer)