Evening star., 1955-02-09
Age Of Solar System
Put at 4.6 Billion Years
Atomic Disintegrotion in
Meteorites Helps Fix FiqurA
By Thomas R. Henry


Our part of the universe is at least
4.6 billion years old.
This great age has been determined
for two stony meteorites picked up in
Iowa and Kansas by chemists using
the facilities of the Argonne Laboratory
of the Atomic Energy Commission at
the University of Chicago, according to
a report recently issued by the commits
sion.
The age determination was made by
measuring the minute amounts Of O
radioactive form Of potassium and
stable form of the rare gas known as
argon contained In these visitors" from
the skies. Potassium atoms "blow up"
and become argon. The rate of this
disintegration Is known, so that the
relative amounts present give measure
Of the time that has elapsed since the
meteorite solidif1ed enough to retain
the gas.
The determination depended on
methods developed by Atomic Energy
Commission scientists for precise de-
termination of extremely minute
amounts Of elements.
Part Of Solar System.
Meteorites are part of the solar Sys-
tenn, like the earth. They may be the
remnants of some anciently disrupted
planet. Presumably both they and the
earth were formed out of the same
"sun mixture" of elements in the be-
ginning, and 1t is quite likely that they
became solid at about the same time.
- .;,~a &fa kos
age is considered fair measure Of the
age Of the solar system in its present
form and probably of the earth itself.
It is striking, says the commissions
report, that the age obtained for the
two meteorites agrees quite closely with
that obtained for the crust of the earth
by quite different methods. Uranium
in the crust constantly is breaking
down into two forms, or isotopes. Of
lead which chemists can distinguish
precisely from ordinary lead. Thus the
ratio Of radiogenic lead to uranium, the
breakdown rate being known, makes
possible close estimate of the age Of
the rocks in which the two elements
are found.
Earth crust measurements, also car
ried out with extreme precision at the
Argonne Laboratory give an age Of
about as billion years-a difference
of only 100 million years from the age
obtained from the meteorites.
Still a Few Bugs"
Other measurements also are giving
ages of between and billion years
for the material of the solar system,
insofar as it is available for testing.
since 1t came into its present combina-
tions. Admittedly. however, there still
are many bugs" in the method.
In the beginning, presumably, the
"sun-stuff" existed as a primordial gas
in which the atoms of all 90 elements
were mixed fairly evenly. This gas was
In a great cloud presumably extending
to about the limits of the solar system.
There are various theories on how long
1t took this primordial gas to solidify
into the present substance of the plan
cts or what may have happened to the
distribution of the elements In this
solidification.
Up to about Is years ago the age Of
the earth and probably that of the uni
verse were estimated from uranium lead
measurements at little over 2 billion
years. These measurements were based
largely on samples of what perhaps
were the earth's Oldest rocks obtained
from northern Canada and from the
Kola peninsula of northern Russia. This
age also agreed with data-now ad-
mittedly based on false hypothesis
on the rate of the uniterse's expansion.
Age estimates went steadily up and
up with more refined methods Of
measurement, but they now seem to
be settling down at somewhere around
4.6 billion years.