The Early Universe
E
very culture has its own creation myths, and there is of
course the account in Genesis which Biblical funda-
mentalists still take quite literally. But when we come to
consider the origin of the universe from a scientific point
of view, we are faced with immediate difficulties. The
first question to be answered is straightforward enough:
‘Did the universe begin at a definite moment, probably
13,700 million years ago, or has it always existed?’
Neither concept is at all easy to grasp.
The idea of a sudden creation in a ‘Big Bang’ was
challenged in 1947 by a group of astronomers at
Cambridge, who worked out what came to be called the
continuous-creation or ‘steady-state’ theory. In this pic-
ture, the universe had no beginning, and will never come
to an end; there is an infinite past and an infinite future.
Stars and galaxies have limited lifetimes, but as old galax-
ies die, or recede beyond the boundary of the observable
universe, they are replaced by new ones, formed from
material which is spontaneously created out of nothing-
ness in the form of hydrogen atoms. It follows that if we
could look forward in time by, say, ten million million
years, the numbers of galaxies we would see would be
much the same as at present – but they would not be the
same galaxies.
The rate at which new hydrogen atoms were created
would be so low that it would be quite undetectable, but
there were other tests which could be made. If we could
invent a time machine and project ourselves back into the
remote past, we would be able to see whether the universe
looked the same then as it does now. Time machines
belong to science fiction, but when we observe very
remote galaxies and quasars we are in effect looking back
in time, because we see them as they used to be thousands
of millions of years ago. Careful studies showed that con-
ditions in those far regions are not identical with those
closer to us, so that the universe is not in a steady state.
More definite proof came in 1965. If the universe
began with a Big Bang, it would have been incredibly hot.
It would then cool down, and calculations indicated that
by now the overall temperature should have dropped to
three degrees above absolute zero (absolute zero being the
coldest temperature that there can possibly be – approx-
imately 273 degrees C). We should therefore be able to
detect weak ‘background radiation’, coming in from all
directions all the time, which would represent the remnant
of the Big Bang; and in the United States Arno Penzias
and Robert Wilson, using a special type of antenna, actual-
ly detected this background radiation. Theory and observa-
tion dovetailed perfectly, and by now the steady-state pic-
ture has been abandoned by almost all astronomers. We
are back with the Big Bang.
We have to realize that space, time and matter all came
into existence simultaneously; this was the start of ‘time’
and we cannot speculate as to what happened before that,
because there was no ‘before’. We can work back to 10^43
of a second after the Big Bang, but before that all our
ordinary laws of physics break down, and we have to con-
fess that our ignorance is complete. (10^43 is a convenient
way of expressing a very small quantity; it is equivalent to
a decimal point followed by 42 zeros and then a 1.)
If we could go back to the very earliest moment which
we consider, 10^43 of a second after the Big Bang, we
would find an incredibly high temperature of perhaps
1032 degrees C. This is so hot that no atoms could possibly
form. Various forces were in operation, and when these
began to separate there was a period of rapid inflation,
when the universe expanded very rapidly. This lasted from
about 10^36 to 10^32 second after the Big Bang, andstopped when the various forces had become fully separat-
ed. Since then the rate of expansion has been much slower.
At the end of the inflationary period, the universe
was filled with radiation. There were also fundamental
particles which we call quarks and antiquarks, which were
the exact opposites of each other, so that if they collided
they annihilated each other. Had they been equal in num-
ber, all of them would have been wiped out, and there
would have been no universe as we know it, but in fact
there were slightly more quarks than antiquarks, and even-
tually the surplus quarks combined to form matter of the
kind we can understand.
At 10^5 second (or one ten-thousandth of a second)
after the Big Bang protons and neutrons started to form,
and after approximately 100 seconds, when the temperature
had dropped to 1000 million degrees C, these protons and
neutrons began to combine to form the nuclei of the light-
est elements, hydrogen and helium. Theory predicts that
there should have been about ten hydrogen nuclei for every
nucleus of helium, and this is still the ratio today, which is
yet another argument in favour of the Big Bang picture.
At this stage space was filled with a mish-mash
of electrons and atomic nuclei, and it was opaque to
radiation; light could not go far without colliding with an
electron and being blocked. But when the temperature had
fallen still further, to between 4000 and 3000 degrees C, the
whole situation changed. By about 300,000 years after the
Big Bang, most of the electrons had been captured by pro-
tons to make up complete atoms, so that the radiation was
no longer blocked and could travel freely across the growing
universe. Over a thousand million years after this ‘decou-
pling’, galaxies began to form; stars were born, and massive
stars built up heavy elements inside them, subsequentlyATLAS OF THE UNIVERSE
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