The Science Book

244

without end or beginning, and the
prospect of a distinct point of origin
(especially when proposed by a
Catholic priest) was seen as
introducing an unnecessary
religious element into cosmology.
However, Hubble’s observations
were undeniable, and some kind of
model was needed to explain the
expanding universe. Numerous
theories were put forward in the
1930s, but by the late 1940s, just
two remained in play—Lemaître’s
primeval atom, and the rival
“steady state” model, in which
matter was continuously created
as the universe expanded. British
astronomer Fred Hoyle was the
champion of the steady state idea.

In 1949, Hoyle scornfully referred

to the rival theory as a “Big Bang.”

The name stuck.

Making the elements

By the time Hoyle had inadvertently

named the theory, a persuasive

piece of evidence in favor of

Lemaître’s hypothesis had been

published, tipping the balance

GEORGES LEMAÎTRE

Tiny variations have been found in
the cosmic microwave background
radiation—the different colors in this
image show temperature differences
of less than 400 millionths of a Kelvin.

away from a steady state universe.

This was a 1948 paper written by

Ralph Alpher and George Gamow

of the Johns Hopkins University

in the US. It was called The Origin

of Chemical Elements, and

described in detail how subatomic

particles and lightweight chemical

elements could have been produced

from the raw energy of the Big

Bang, in accordance with

Einstein’s equation E = mc^2. But

this theory, later known as Big

Bang nucleosynthesis, explained a

process that could form only the

four lightest elements—hydrogen,

helium, lithium, and beryllium.

Only later was it discovered that

the heavier elements of the

universe are the product of stellar

nucleosynthesis (a process that

takes place inside stars). Ironically,

the evidence showing how stellar

nucleosynthesis worked was to be

developed by Fred Hoyle.

Nevertheless, there was still

no direct observational evidence

to determine the truth of either

the Big Bang or a steady state

universe. Early attempts to test

the theories were made in the

1950s using a basic radio telescope

known as the Cambridge

Interferometer. These tests relied

on a simple principle: if the steady

state theory was true, then the

The radius of space began at zero.

Lemaître theorizes that the universe began with a

“primeval atom,” a theory later dubbed the “Big Bang.”

General relativity leads

Lemaître to predict that

the universe is expanding.

Hubble demonstrates

cosmic expansion.

The discovery of cosmic microwave background radiation

(CMBR) confirms the Big Bang theory.