| The Doppler effect describes the change in frequency and wavelength of waves from a moving source. | Doppler Effect |
| What does the Doppler effect describe? | The change in frequency and wavelength of waves from a moving source. |
| When an ambulance is moving towards you, its siren has a higher pitch than normal. | Ambulance Siren Towards |
| What happens to the pitch of an ambulance siren when it moves towards you? | It has a higher pitch than normal. |
| When an ambulance is moving away from you, its siren has a lower pitch than normal. | Ambulance Siren Away |
| What happens to the pitch of an ambulance siren when it moves away from you? | It has a lower pitch than normal. |
| When a wave source is moving towards an observer, the waves bunch together. The wavelength decreases, and the frequency increases. This makes sound waves have a higher pitch and makes light waves more blue. | Waves Moving Towards |
| What happens to waves when the source moves towards an observer? | The waves bunch together, wavelength decreases, frequency increases, making sound waves higher pitch and light waves more blue. |
| When a wave source is moving away from an observer, the waves are spread apart. The wavelength increases, and the frequency decreases. This makes sound waves have a lower pitch and makes light waves more red. | Waves Moving Away |
| What happens to waves when the source moves away from an observer? | The waves spread apart, wavelength increases, frequency decreases, making sound waves lower pitch and light waves more red. |
| The Universe contains a huge number of galaxies. | The Universe contains a huge number of galaxies. |
| What does the Universe contain a huge number of? | Galaxies. |
| A galaxy is made of millions and millions of solar systems. | Composition of a Galaxy |
| What is a galaxy made of? | Millions and millions of solar systems. |
| Our Solar System is in a galaxy called the Milky Way. | Milky Way Galaxy |
| What is the name of the galaxy that contains our Solar System? | The Milky Way. |
| The light from distant galaxies is red-shifted. | Red-Shifted Light |
| What is the phenomenon where light from distant galaxies shifts to a longer wavelength? | Red-shift. |
| Light from a star does not include all the wavelengths of the electromagnetic spectrum because elements in the star absorb some of the wavelengths. | Star Light Wavelengths |
| Why does light from a star not include all the wavelengths of the electromagnetic spectrum? | Because elements in the star absorb some of the wavelengths. |
| Viewed from Earth, some of the colours are missing, and we see dark lines where they should be. | Missing Colours |
| What do we see when some colours of light from a star are missing? | Dark lines where the colours should be. |
| Different elements absorb different wavelengths of light. When we can't see a particular colour, we know it has been absorbed by a particular element. | Element Absorption |
| How do we know which element has absorbed a particular colour of light? | Different elements absorb different wavelengths, so when a colour is missing, it indicates absorption by a specific element. |
| The lines for each element always have the same spacing. | Line Spacing |
| What is consistent about the lines representing each element's absorption? | The lines always have the same spacing. |
| With light from distant galaxies, the lines are closer to the red end of the spectrum. They have shifted to a longer wavelength, known as red-shift. | Red-Shift in Distant Galaxies |
| What happens to the absorption lines in the light from distant galaxies? | They shift to the red end of the spectrum, indicating a longer wavelength, known as red-shift. |
| Red-shift shows that space is expanding. | Red-Shift and Expansion |
| What does red-shift indicate about space? | It shows that space is expanding. |
| Red-shift means that the galaxy or star being observed is moving away from the Earth. | Red-Shift Meaning |
| What does red-shift mean about the movement of a galaxy or star? | It means the galaxy or star is moving away from the Earth. |
| The expanding space between the galaxy or star and the Earth stretches out the wavelengths and causes the shift. | Wavelength Stretching |
| What causes the stretching of wavelengths in red-shift? | The expanding space between the galaxy or star and the Earth. |
| The further away a galaxy is, the more the light is shifted to the red end of the spectrum. The further the galaxy, the bigger the increase in wavelength. | Distance and Red-Shift |
| What happens to the red-shift as a galaxy gets further away? | The light is more shifted to the red end of the spectrum, indicating a bigger increase in wavelength. |
| This shows that more distant galaxies are moving away from us faster than closer galaxies. | Distant Galaxies |
| What does the red-shift of distant galaxies indicate about their movement compared to closer galaxies? | More distant galaxies are moving away faster than closer galaxies. |
| What does the red-shift of galaxies provide evidence for? | That the Universe is expanding. |
| Since 1998, observations of supernovae have shown that distant galaxies are moving away faster and faster. | Supernova Observations |
| What have observations of supernovae since 1998 shown? | That distant galaxies are moving away faster and faster. |
| Both the Big Bang and Steady State theories agree that the Universe is expanding. Red-shift provides evidence to support both theories. | Supporting Theories |
| Which two theories agree that red-shift shows the Universe is expanding? | The Big Bang and Steady State theories. |
