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Stars and the Universe

The Universe - Big Bang - Red-Shift.

The big bang theory developed as an attempt to
explain the observation that light in
line spectra from other galaxies is red-shifted.
This means that light from other galaxies
appears to be at a longer wavelength than it is on Earth.

It is called a red-shift because the colour red is at
the longer wavelength end of the visible light spectrum.
If light appeared to be at a shorter wavelength,
it would be called a blue-shift.

It is accepted by scientists as a fact that
light from other galaxies has a red-shift.
The further away the galaxy, the greater the red-shift.
The fact that this light is at a longer wavelength than expected
requires
an explanation. The most popular explanation is
that other galaxies are moving away from us (see next page).

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