Listen&Learn: Redshift

Learn about the effect that causes objects to change colour.

Pre-listening vocabulary

• observer: a person who is watching something
• wavelength: the distance between the peaks of a light or sound wave
• visible spectrum: all of the light waves that humans can see
• pitch: how high or low a sound is
• expand: to grow larger
• solar system: the planets that orbit the Sun

Listening activity

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Gapfill exercise

Redshift is an created by light waves. It causes the colour of an object to become redder as it moves from an observer. This is because red light has the longest wavelength of all the colours on the visible spectrum. Redshift is not something that humans often see, because an object must be very fast to visibly change colour. However, we can observe a similar effect with sound waves, when the pitch of a car horn changes as the car drives away. Redshift is important because it has helped astronomers make about the universe. In 1929, the redshift of caused astronomer Edwin Hubble to discover that the universe is expanding. Today, astronomers also use redshift to find the locations of planets outside of our solar system.

Comprehension questions

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Discussion/essay questions

1. Redshift is one example of how reality can depend on our interpretation. While an observer standing still might be able to see an object change colour, an observer moving at the same speed as the object would not. Can you think of some other situations where different people might interpret reality differently?

Transcript

Redshift is an effect created by light waves. It causes the colour of an object to become redder as it moves away from an observer. This is because red light has the longest wavelength of all the colours on the visible spectrum. Redshift is not something that humans often see, because an object must be travelling very fast to visibly change colour. However, we can observe a similar effect with sound waves, when the pitch of a car horn changes as the car drives away. Redshift is important because it has helped astronomers make observations about the universe. In 1929, the redshift of galaxies caused astronomer Edwin Hubble to discover that the universe is expanding. Today, astronomers also use redshift to find the locations of planets outside of our solar system.