BIRTH CERTIFICATE FOR EARTH.

Timaru Herald, Volume CXXV, Issue 18620, 16 July 1930, Page 12

BIRTH CERTIFICATE FOR EARTH.

TWO THOUSAND MILLION YEARS A couple of centuries ago the earth was generally believed to be little more than 6,000 years old. Then strange discoveries began to be made. Excavations in Egypt took the history of civilised mankind back to much more than 6,000 years, and the remains of prehistoric man proved that the beginning of human life dated back to a far more remote period. Investigatiaon showed that life in some form had been in existence upon the earth not for thousands, but for millions of years. The geologist found that the rock formations he studied must have been not mere millions, but thousands of millions of years in the making. It became clear then, that we should have to probe almost inconceivably far into the past to discover the earth’s birthday. Was there any way of finding out just how old the world could be? The first man who set out to discover the date of the earth’s birthday was Halley, the astronomer.

The reason why the sea is salt is that every river in the world is carrying down to it quantities of salts that its waters have dissolved from the land. Evaporation removes water from the sea, but it leaves the salt behind. Thus every year the sea is becoming slightly salter. The amount of salt in the sea can be estimated, and it is possible to calculate how long it would have taken to bring this down from the land. Though no very exact results can be obtained, in this way calculation proves that the earth’s age must be many hundreds of millions of years. Then came the turn of the rocks. Many of these are simply hardened mud which has been deposited year after year and century after century. We know that the. earth is increasing in size, for to find the cities of the past we have to dig away the covering that the centuries have placed over them. The rate at which the covering layers have been deposited is easily calculated. In many places, too, rock's m the making are to be found, and it is possible to work out from observation just how rapidly they grow The rocks themselves show us that the earth must be more than 2,000 000 000 years old. ’

One of the most remarkable dis-

coveries of recent years is the radioactive metal, uranium, which gradually changes into lead. The rate at which this process is carried out is well known, and it is invariable. By taking rocks which contain both uranium anu lead, and finding the proportion of each metal now existing in them, the length of time necessary to bring about the present state of affairs is not difficult to calculate. Such a calculation shows that the earth must have been solid not far short of 2,000,000,000 million years ago. The paths of the earth round the sun and the moon round the earth are not what they were originally. Science can reconstruct ' ,wl m and discover the ■ needed to give them their present shapes. All these methods show (comments the “Cape Argus”) that the age of the earth must be more than 1,000.000.000 years, and fewer than 4,000.000,000 years. We shall, then, net be farwrong if we fix the earth's birthday about 2,000.000,000 years ago.