The Science Book

98 JAMES HUTTON

F

or millennia, human

cultures have pondered

the age of Earth. Before

the advent of modern science,

estimates were based on beliefs

rather than evidence. It was not

until the 17th century that a

growing understanding of Earth’s

geology provided the means to

determine the planet’s age.

Biblical estimates

In the Judaeo-Christian world, ideas

about Earth’s age were based on

descriptions in the Old Testament.

However, since these texts only

presented the creation story in brief

outline, they were subject to much

interpretation, especially over the

complex genealogical chronologies

that followed the appearance of

Adam and Eve.

Best known of these Biblical

calculations is that by James

Ussher, the protestant Primate of all

Ireland. In 1654, Ussher pinpointed

the date of Earth’s creation to the

night preceding Sunday October

23, 4004 BCE. This date became

virtually enshrined in Christian

culture when it was printed in

many Bibles as part of the Old

Testament chronology.

IN CONTEXT

BRANCH

Geology

BEFORE

10th century Al-Biruni uses

fossil evidence to argue that

land must once have been

under the sea.

1687 Isaac Newton argues

that Earth’s age can be

calculated scientifically.

1779 The Comte de Buffon’s

experiments suggest an age

of 74,832 years for Earth.

AFTER

1860 John Phillips calculates

Earth’s age at 96 million years.

1862 Lord Kelvin calculates

Earth’s cooling to produce an

age of 20–400 million years,

later settling on 20–40 million.

1905 Ernest Rutherford uses

radiation to date a mineral.

1953 Clair Patterson puts

Earth’s age at 4.55 billion years.

All the years from the

creation of the world amount

to a total of 5,698 years.

Theophilus of Antioch

A scientific approach

During the 10th century CE,

scholars in Persia began to

consider the question of Earth’s

age more empirically. Al-Biruni,

a pioneer of experimental science,

reasoned that if marine fossils were

found on dry land, then that land

must once have been under the

sea. Earth, he concluded, must be

evolving over long periods of time.

Another Persian scholar, Avicenna,

suggested that layers of rock had

been laid down one upon another.

In 1687, a scientific approach

to the problem was suggested

by Isaac Newton. He argued that

it would take a large body like

Earth about 50,000 years to cool

if it were made of molten iron.

He derived this figure by scaling

up the cooling time taken for

a “globe of iron of an inch in

diameter, exposed red hot to

open air.” Newton had opened

the door to a scientific challenge

to previous understandings of

Earth’s formation.

Following Newton’s lead, French

naturalist Georges-Louis Leclerc,

Comte de Buffon, experimented

with a large ball of red-hot iron, and

showed that if Earth were made of

molten iron, it would take 74,832

years to cool. In private, Buffon

thought that Earth must be far

Landscapes are continually

denuded and the debris

deposited into the sea.

Yet this process does not

lead to loss of the land

surface...

There is no vestige

of a beginning and no

prospect of an end.

...because new continents

are formed from materials

derived from previous

continents by the same

endless processes.