P16 Space: Red-Shift and the Big Bang

Evidence that the universe is expanding

• The light from most distant galaxies have very long wavelengths that have increased.
• The wavelengths have all shifted to the red end of the spectrum, so it is called red-shift.
• This suggests that the source of light is moving away.
• More distant galaxies have greater red-shifts than nearer ones, which means that more distant galaxies are moving away faster.

the balloon model:

• The expanding universe can be explained using a balloon model.
• If a balloon is covered with pompoms, as you blow air into it and it stretches, the pompoms will move away from each other.
• However, there are limitations…