When a galaxy is moving away from us the WAVELENGTH of the light from it changes – the light becomes redder. This is called RED SHIFT:
By seeing how much the light has been red-shifted, you can work out how quickly it’s moving away. The greater the red-shift the faster it’s moving away. From the observations of different red-shifts of different galaxies we know that:
The more DISTANT the galaxy, the FASTER it moves away from us
Big Bang Theory
The Earth and the sun are a similar age. But the universe is about 3x older.
Refer to I/GCSE Physics, When Scientists trace the paths of galaxies, they all appear to be moving away from the same point. The best theory for this is the BIG BANG THEORY, which says that the universe started with a huge explosion 14,000 million years ago.
The ultimate fate of the Universe this is because the future depends on the amount of MASS in the Universe.
- If there is NOT ENOUGH MASS, the universe will keep expanding
- If there is TOO MUCH MASS, gravity will be strong enough to pull everything back together and the universe will collapse with a big crunch.
In I/GCSE Physics, measuring the amount of mass in the Universe is very difficult, so it’s ultimate fate.
That's the end~ Thanks for watching.