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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 the
wavelength of light in line spectra 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 from other galaxies appeared to be at a
shorter wavelength, it would be called a blue-shift.

It is accepted by scientists as a fact that light that has
come from other galaxies has a red-shift.
The further away the galaxy, the greater the red-shift.
An explanation is required that would account for the
red-shift. The most popular explanation is that other
galaxies are moving away from us (see the next page).

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