The Science Book

243

See also: Isaac Newton 62–69 ■ Albert Einstein 214–21 ■
Edwin Hubble 236–41 ■ Fred Hoyle 270

neither expanding nor contracting.
General relativity indicated that
the universe should collapse under
its own gravity, so Einstein fudged
his own equations by adding a
term known as the cosmological
constant. Einstein’s constant
mathematically counteracted the
gravitational contraction to produce
the presumed static universe.

Famously, Einstein later called the

constant his greatest mistake,

but even at the time he proposed

it there were some who found it

unsatisfactory. The Dutch physicist

Willem de Sitter and Russian

mathematician Alexander

Friedmann independently

suggested a solution to general

relativity in which the universe was

expanding, and, in 1927, Belgian

astronomer and priest Georges

Lemaître reached the same

conclusion, two years ahead of

Hubble’s observational proof.

Beginning in fire

In an address to the British

Association in 1931, Lemaître

took the idea of cosmic expansion

to its logical conclusion, suggesting

that the universe had sprung from

a single point that he called the

“primeval atom.” The response

to this radical idea was mixed.

The astronomical establishment

of the time was attached to the

idea of an eternal universe ❯❯

A PARADIGM SHIFT

Georges Lemaître

Born in Charleroi, Belgium, in

1894, Lemaître studied civil

engineering at the Catholic

University of Louvain and

served in World War I before

returning to academia, where

he studied physics and

mathematics as well as

theology. From 1923, he

studied astronomy in Britain

and the United States. On his

return to Louvain in 1925 as

a lecturer, Lemaître began

to develop his theory of an

expanding universe as an

explanation for the redshifts

of the extragalactic nebulae.

First published in 1927, in

a little-read Belgian journal,

Lemaître’s ideas took off

after he published an English

translation with Arthur

Eddington. He lived until

1966—long enough to see

proof that his ideas were

correct with the discovery

of the cosmic microwave

background radiation (CMBR).

Key works

1927 A Homogeneous Universe

of Constant Mass and

Growing Radius Accounting

for the Radial Velocity of

Extragalactic Nebulae

1931 The Evolution of the

Universe: Discussion

The first stages of the
expansion consisted of a
rapid expansion determined
by the mass of the initial atom,
almost equal to the present
mass of the universe.
Georges Lemaître

Expanding universe

Accelerating

expansion

Big Bang

Time Slowing expansion

(~15 billion years)

Present

Since the Big Bang 13.8 billion years ago, the expansion of the
universe has been through different phases. There was an initial
period of rapid expansion known as inflation. After that, expansion
slowed, then started to speed up once more.

Inflation