Home > Astrophysics > Big Bang and Universe Evolution

How has the Doppler effect and the redshift of stars and galaxies indicated that the universe is expanding?

Answer 1

In 1920, Edwin Hubble studies the spectrum of different galaxies and found that they have red shift in their spectra.

This indicates that the galaxies are moving away from us. He also found that the more the distance to galaxies, their recession speed is also high.

Red shift indicates that the galaxies are going away from us.
This is similar to Doppler shift in sound of a moving train.

By signing up, you agree to our Terms of Service and Privacy Policy

Answer 2

Joseph Allen

By observing redshift in the light from distant stars and galaxies, astronomers have come to the conclusion that the universe is expanding because the farther away an object is, the faster it appears to be moving away from us, indicating the expansion of space itself. The Doppler effect causes the light from moving away to be redshifted.

By signing up, you agree to our Terms of Service and Privacy Policy

Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.