of the Earth
By Don Ware
we take for the history of nature is only the very incomplete history
of an instant" - Denis Diderot
In a moment of weakness I turned the TV on (the only screen I usually
watch is one with a computer attached to it) a couple of nights ago and
watched a religious program on the age of the Earth. The "scientist"
was explaining how all of our current methods of dating elements, estimating
the rate of erosion, and the rate of sedimentary build up were completely
wrong in determining the age of the Earth. The age of the Earth, he concluded,
can be no more than 6,000 years old, with dinosaurs roaming the Earth
as little as 4,000 years ago.
I was intrigued. How do we know with certainty how old the Earth really
is? We do know that the Earth is at least 5,000 years old as we have written
records dating back to 3,000 BC, or BCE if you prefer.
I decided to look back into the records to see how our present day notion
that the Earth is 4.6 billion years old was arrived at.
Our western civilization held that the Earth was 6,000 years old right
up to the 1800's. They held this belief based on faith in the teachings
of the Bible, but science is not based on faith, but rather on observations
A French scholar, Bernard Palissy who lived from 1510-1589 believed the
Earth was much older based on his observations that rain, wind, and tides
were the cause for much of the present-day appearance of the Earth. He
wrote that, these forces could not work over such a short period of time
to produce the changes. He was burned at the stake in 1589. A bad time
for scientific inquiry.
Another was Thomas Burnet, a member of the English clergy, who lived from
1635-1715. He had written a book around 1681 supporting the idea of a
worldwide flood, but in 1692, he wrote another book in which he questioned
the existence of Adam and Eve, and that ended his career.
The notion that the Earth is much older than 6,000 years comes from a
book written in 1795 by James Hutton, called "The Theory
of the Earth" Hutton presented evidence that slow,
gradual changes acting over a long period of time were responsible for
shaping much of the Earth's landmasses. It took almost 50 years for science
to begin to accept Hutton's ideas. Hutton's ideas became known as uniformitarianism.
Science began to study the changes taking place at the present time and
worked out how rapidly those changes were happening. The assumption is
that if the rate of change remains more or less constant, then the time
it takes to create the change could be estimated mathematically.
Edmund Halley was the first person to attempt to calculate the rate of
change. His idea was to determine the rate at which the oceans became
salty. He observed that the fresh water rivers carried salt, dissolved
from the land during the process of erosion, to the oceans. Halley thought
that at one time the oceans must have been free of salt, and the salt
contained in them must have been carried there by the rivers. So he set
out to find out how much salt the rivers carried into the oceans each
year. He arrived at an age of 1 billion years for the oceans to reach
their present levels of salinity.
In 1896, only one hundred years ago, French physicist, Antoine Henri Becquerel
discovered by accident that atoms of uranium gave off radiation. Marie
Currie studied the phenomenon further and concluded that the radiation
was the result of radioactivity. In 1915, Frederick Soddy discovered that
over time the radioactive atoms of uranium and thorium broke down into
simpler elements. This decay continued until lead was produced, which
is not radioactive, and the decay stopped.
Ernest Rutherford, working with Soddy, showed that every radioactive element
had a half-life. This being the amount of time it takes for half of the
radioactive atoms to be lost. The half life of uranium turns out to be
around 4.5 billion years, thorium has a half life of 14 billion years.
This set an upper limit for the age of the Earth. If the Earth was a trillion
years old, no radioactive uranium could exist.
Bertram Boltwood an American physicist worked out how to calculate the
age of rocks containing uranium and lead. Boltwoods method took into account
that the rock might contain some naturally occurring lead. He was able
to isolate an isotope which was not present in lead formed through radioactive
decay, but was only present in lead formed naturally. Using this method
some rocks were dated at more than 1 billion years old. In 1931, rocks
were found that were 3.8 billion years old in Greenland.
The point: There is some evidence today that
scientific inquiry is on the wane, that people seem to accept the mystical
more readily than the empirical. Our view of the universe is based
on what we see and what we reason the cause can be to explain what we
see. This is the difference between humans and animals.