Free Parallel Worlds by Michio Kaku Page B

chain, starting with hydrogen, that could be built by simply
adding successively more particles to the hydrogen atom. The entire Mendeleev
periodic chart of the chemical elements, he believed, could be created from the
heat of the big bang.
    Gamow and his
students reasoned that because the universe was an incredibly hot collection of
protons and neutrons at the instant of creation, then perhaps fusion took place,
with hydrogen atoms being fused together to produce helium atoms. As in a
hydrogen bomb or a star, the temperatures are so hot that the protons of a
hydrogen atom are smashed into each other until they merge, creating helium
nuclei. Subsequent collisions between hydrogen and helium would, according to
this scenario, produce the next set of elements, including lithium and
beryllium. Gamow assumed that the higher elements could be sequentially built
up by adding more and more subatomic particles to the nucleus—in other words,
that all of the hundred or so elements that make up the visible universe were
"cooked" in the fiery heat of the original fireball.
    In typical
fashion, Gamow laid out the broad outlines of this ambitious program and let
his Ph.D. student Ralph Alpher fill in the details. When the paper was
finished, he couldn't resist a practical joke. He put physicist Hans Bethe's
name on the paper without his permission, and it became the celebrated
alpha-beta-gamma paper.
    What Gamow had
found was that the big bang indeed was hot enough to create helium, which makes
up about 25 percent of the universe, by mass. Working in reverse, one
"proof" of the big bang can be found by simply looking at many of the
stars and galaxies of today and realizing that they are made of approximately
75 percent hydrogen, 25 percent helium, and a few trace elements. (As David
Spergel, an astrophysicist at Princeton, has said, "Every time you buy a
balloon, you are getting atoms [some of which] were made in the first few
minutes of the big bang.")
    However, Gamow
also found problems with the calculation. His theory worked well for the very
light elements. But elements with 5 and 8 neutrons and protons are extremely
unstable and hence cannot act as a "bridge" to create elements that
have a greater number of protons and neutrons. The bridge was washed out at 5
and 8 particles. Since the universe is composed of heavy elements with a great
many more than 5 and 8 neutrons and protons, this left a cosmic mystery. The
failure of Gamow's program to extend beyond the 5-particle and 8-particle gap
remained a stubborn problem for years, dooming his vision of showing that all
the elements of the universe were created at the moment of the big bang.
    MICROWAVE BACKGROUND RADIATION
    At the same
time, another idea intrigued him: if the big bang was so incredibly hot,
perhaps some of its residual heat is still circulating around the universe
today. If so, it would give a "fossil record" of the big bang itself.
Perhaps the big bang was so colossal that its aftershocks are still filling up
the universe with a uniform haze of radiation.
    In 1946, Gamow
assumed that the big bang began with a superhot core of neutrons. This was a
reasonable assumption, since very little was known about subatomic particles
other than the electron, proton, and neutron. If he could estimate the
temperature of this ball of neutrons, he realized he could calculate the amount
and nature of radiation that it emitted. Two years later, Gamow showed that
radiation given off by this superhot core would act like "black body radiation."
This is a very specific type of radiation given off by a hot object; it absorbs
all light hitting it, emitting radiation back in a characteristic way. For
example, the Sun, molten lava, hot coals in a fire, and hot ceramics in an oven
all glow yellow-red and emit black body radiation. (Black body radiation was
first discovered by the famed maker of porcelain, Thomas Wedgwood, in 1792. He
noticed that when raw materials were baked in his ovens, they