Brainlag PlusWhy light from distant galaxies is shifted towards red, why more distant galaxies move away faster, and how this, with the cosmic microwave background, supports the Big Bang theory.
Stretched light
Hydrogen and other elements absorb light at exact wavelengths, so a spectrum has dark lines in a pattern astronomers know from the laboratory.
In light from distant galaxies the same pattern appears, but moved towards the red (longer wavelength) end.
This red-shift is an increase in the observed wavelength. It means the galaxy is moving away from us: the waves are stretched out.
The rest of this lesson and its 10 practice questions are in Plus.
Screen 1 of 4, free to read.
- 10 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards