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Olbers’ paradox is often quoted as being consistent with the big bang theory because
it is a proposition claiming that since the sky at night is dark the universe must
have a finite size and finite age. It is argued that every line of sight must end
upon a star. Although the light from a star decreases with distance according to
the inverse square law, the number of stars increases with distance and the two
cancel out. So in an infinite universe with an infinite number of stars there must
be the same amount of light shining upon every portion of the Earth. From this it
is argued that the whole surface of the Earth should be as hot as the surface of
a star.
Olbers’ paradox has been argued over by numerous eminent scientists and they all
seem to agree that if the universe was eternal and extended to infinity then both
the night and day skies should be as bright as the surface of the Sun. They argue
that the big bang theory explains the paradox and that there are three reasons that
the night sky is dark.
The first is the universe is finite in size and that there are therefore not an
infinite number of stars.
The second is that because the universe is less than 14 billion years old there
cannot be light coming from stars older than this.
The third reason is because the universe is expanding the light is stretched and
somehow this causes it to lose energy so that by the time the light from distant
stars reaches us it has lost all of its energy.
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Olbers’ paradox would appear to rule out FET which predicts
an eternal and infinite universe. However, you do not need FET
to explain why the night sky must be darker than the day sky but just a bit of common
sense. If we take away our Sun for the moment and assume that the universe is uniform
on the very large scale we can see that there is the same amount of starlight shining
down on both sides of the Earth. If we now replace the Sun in its proper position
we see that its light only shines on the day side of the Earth.
Because the nearest star to us is around 200,000 times further away than the Sun
the amount of light shining on the day lit side of the Earth is always 4x1010 times
greater than that on the night side, neglecting any reflection from the Moon.
However, the reason why we can have a universe that is infinite in extent and time
does need explaining by FET.
The reason that the light from all the stars in an infinite universe do not make
much contribution to the total amount of visible light shining on both sides of
the planet is that light loses energy as it travels through space as explained in
FET as a real loss of energy and not just a stretching
of a wavelength by expanding space.
Therefore the radiation from stars further away than 1011 light years has either
disappeared back into the continuum or dropped below the visible region of the spectrum
before it reaches us. Hence it does not matter how many stars are beyond this limit.
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