On wherever we look and second, this would also

On a clear moonless night, we can see
Venus, Mars, Jupiter and Saturn shining brightly. As the earth goes around the
sun, the planets and the stars change their position in the sky.  Alpha Centauri, the nearest star from earth,
is four light years away. Our sun, meanwhile, is only eight light minutes away.

The contemporary depiction of the universe
was devised by Edwin Hubble in 1924. Hubble disclosed that our galaxy, Milky
Way, is not the only one. There are many others and there are vast empty spaces
between them.  Our galaxy is 100,000
light years across and it is rotating slowly. Hubble also postulated that the
brightness of a star depends on its luminosity and distance from earth. He
published in 1929 that the farther the galaxy, the faster is it moving away.
This means that the universe is not static. It could be expanding because the
distance between galaxies is growing over time.

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This discovery was one of the greatest
discoveries in the twentieth century. Even Newton and Einstein did not think it
possible. It was only Alexander Friedmann who set about to explain this
expansion. He derived his assumption on two arguments. First, the universe
looks identical wherever we look and second, this would also be true if we were
observing from anywhere else in space.

Friedmann’s prediction was supported by
Arno Penzias and Robert Wilson in 1965 when they tested a very sensitive
microwave detector. They have tracked an extra noise which could come from outer
space since the frequency is the same for all directions. It may even come from
beyond the Solar System because the radiation is consistent throughout the
year. At the same time, Bob Dicke and Jim Peebles suggested that the glow of
the early universe should be visible from earth in the present because it
should only be reaching us now. However, the expanding universe means that this
light had shifted immensely that it would only be perceived as microwave
radiation.