Galactic Red-shift Flashcards

All 6 cards in this deck

What is red-shift?

An increase in the observed wavelength (decrease in frequency) of light from an object moving away from us.

What happens to the absorption lines in the spectrum of a galaxy that is moving away from Earth?

They move towards the red end of the spectrum compared with the same lines measured on Earth.

How does the red-shift of a galaxy depend on its distance from Earth?

The further away the galaxy, the greater its red-shift.

What does a large red-shift tell you about a galaxy's recession velocity?

It is moving away from us at a high speed — the bigger the red-shift, the faster the recession velocity.

Why is the red-shift of galaxies evidence that the Universe is expanding?

Almost all galaxies are moving away from us and from each other, and the most distant move fastest — so space itself is expanding.

True or false? Red-shift shows that the Earth is at the centre of the Universe because all galaxies move away from us.

False. Galaxies are moving away from each other everywhere; every observer would see the same red-shift.