How old is the Solar System?
The planets were whirling merrily around the sun a million years ago. This heavenly hoedown has been going on for several billion years and, we are told, it will continue for billions of years to come. Nevertheless, this wonderful Solar System of ours had a beginning and at some remote time in the far future it will come to an end.
The story of our Solar System is a tantalizing problem and the best brains of science have tried to solve it. So far, no one has been able to prove any exact dates on the age of our solar family. But the experts have suggested several reasonable theories and it may be that the exact details will never be known.
A theory, of course, is a sort of educated guess. It is backed up with a lot of reasonable evidence and mathematics, and it takes into account all we know of the subject matter at this time. Provable facts, however, are missing and a theory is thrown out when it quarrels with the known facts of its subject matter. Several theories of the history of the Solar System were discarded when new information could not be fitted into the explanation.
Most experts are agreed in general on a theory of the Solar System, but new information may come along to make them change their minds. The present theory grew out of several older theories, taking the most reasonable factors from all of them. It is backed up by a wealth of mathematics and detailed knowledge of the heavenly bodies.
The present theory takes us back five billion years. At this time, it suggests, the unborn Solar System was a hazy ball of dust and gases.
In the next few hundred million years, things began to change. The bulk of the material, mostly hydrogen and helium gas, began to concentrate in the center of the fuzzy cloud. Our sun was being formed.
Some of the cloudy dust was left whirling in a wide saucer around the young star. Certain forces caused this dusty debris to congeal in wads of solid material which have been called protoplanets. These embryo planets grew bigger and the Solar System more or less as we know it took shape. This was perhaps a little more than four billion years ago.
Certain rocks in the earth’s crust have been proved to be almost three billion years old. The earth, then, must be much older than this because the rocky crust did not form until the young planet began to cool. The scientists estimate that our old world has had between three and four billion birthdays. It was born along with the rest of the Solar System which means that the heavenly hoedown has been whirling for not longer than five billion years.