BRAINCAKEThe Expanding Universe
Almost every galaxy shows a red shift, and the red shift increases with distance (Hubble's law). This is interpreted as meaning that the universe is expanding.
It is not that galaxies are flying outwards from a centre, with us at the middle. Instead space itself is expanding, carrying galaxies apart. Every galaxy sees all the others moving away, with more distant ones receding faster, so there is no centre and no edge. A common model is dots drawn on a balloon: as it inflates, every dot moves away from every other dot, and dots twice as far apart separate twice as fast.
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Key terms in this lesson
- big bang
- The extremely hot, dense state from which the universe began expanding around 14 billion years ago.
More in Space
- White Dwarfs, Neutron Stars and Black Holes
- Trigonometric Parallax
- Standard Candles
- The Doppler Effect and Red Shift
- Hubble's Law
- The Age of the Universe
- Dark Matter
- The Fate of the Universe
All 18 lessons in Space · All Edexcel A-level Physics topics