Our Sun is an average star in the Universe. 100,000 crore such stars
make the Milky Way Galaxy which is just an average galaxy. There are again
10,000 crore such galaxies in the known Universe. The known Universe has a
diameter of about 1380 crore light years. We are prefixing it with known
because we do not know what lies beyond this. Perhaps a vast empty area with
properties unknown to us, and then maybe another Universe, and so on. Even if
our science develops for another million years (looks unlikely with Nuclear
Weapons around) still we would not be able to fathom the secrets of this cosmic
whole.
What is the origin of the known Universe? Most of the Cosmologists have
accepted the Big Bang theory as the most plausible explanation for the formation
of the Universe. This was propounded by the Belgian Physicist and a Roman
Catholic Priest Abbe Georges Lemaitre in 1927. As per this theory the entire
matter in the Universe is concentrated as one single mass a long time ago. At
that point of time there was neither space nor time and we cannot even imagine
what is outside this mass. Space and time are relative concepts and when the
entire Universe is in a single mass, then they cannot be measured at all and
cease to have any meaning.
As such large amount of matter together gives rise to high gravitational
attraction; all the matter got attracted towards its center. As the mass shrunk
on account of the huge gravitational forces an enormous amount of heat was
generated. The statistics of this Primeval atom are mind boggling. A cubic centimetre
of matter from it would have weighed some 100 million tons.
Matter becomes hotter as it constricts and colder when it expands and in
this concentrated primeval atom the temperatures would have been so enormous
that even atoms did not exist and neither did protons and electrons. The
temperature would have been 100 billion degrees Kelvin one hundredth of a
second after the Big Bang.
Only the neutrons remained in this primeval state and scientists have
named this primeval matter as Neutronium. It would not have been possible for
the matter to be in this intensely hot state for long and it would have
exploded only in a fraction of time. The massive explosion threw matter in all
directions and with the expansion they have cooled slowly to form atoms and
later coalesce into stars and solar systems and planets.
Atoms started forming only about 377,000 years after the Big Bang which
is estimated to have occurred some 14 billion years ago. Scientists have
estimated the time when that single mass exploded by simply projecting back the
possibility of an explosion and counting back from now.
There is an indirect proof for the explosion of the primeval atom (what
else can we call it?) and it is known as Microwave Background Radiation.
American radio astronomers Penzias and Wilson found in 1964 that in whichever
direction they turned their radio antenna, a radiation (later named as
Microwave background variation) not corresponding to any star or a galaxy or an
object is found in all directions of the Universe with the same wavelength and
frequency. This relates to a certain homogenous temperature throughout the
Universe and this can be extrapolated to the Big Bang.
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