196
IT TOOK LESS THAN
AN HOUR TO MAKE
THE ATOMIC NUCLEI
THE PRIMEVAL ATOM
IN CONTEXT
KEY ASTRONOMERS
George Gamow (1904 –1968)
Ralph Alpher (1921–2007)BEFORE
1939 Hans Bethe describes
two ways in which helium can
be made from hydrogen in stars.AFTER
1957 Fred Hoyle and
colleagues set out eight
processes by which chemical
elements can be synthesized
from other elements in stars.
1964 German−US physicist
Arno Penzias and US
astronomer Robert Wilson
discover the cosmic microwave
background radiation.1970s The mass of atom-
based matter (made of protons
and neutrons) as calculated by
Big Bang nucleosynthesis is
found to be much less than the
observed mass of the universe.
This puzzle is largely resolved
by suggesting the existence
of dark matter.I
n 1931, Georges Lemaître
suggested that the universe
originated from the explosion
of an initial, extremely dense,
“primeval atom” and has been
expanding ever since—now known
as the Big Bang theory. However,
by the mid 1940s, the theory was
in need of additional evidence to
sustain its credibility.
A Ukrainian physicist named
George Gamow began thinking
about conditions at the start of
the universe as it was proposed by
Lemaître. He quickly realized thatIt took less than an hour
to make the atomic nuclei.If the Big Bang theory is right, during the universe’s
first few moments, temperatures were exceedingly high.For a short window of time, conditions were right for
protons and neutrons to combine to form atomic nuclei.it would have been unimaginably
hot. Matter would have consisted
of a frenzy of elementary particles
(particles that cannot be broken
down into smaller particles)—
considered at that time largely to
comprise protons, neutrons, and
electrons. Temperatures would have
been too high for these particles
to join up, except very briefly.
However, after several seconds of
existence, the universe would have
expanded and cooled to the point
where protons and neutrons might
be held together by an interaction