Science: The Great Event

In the beginning, says one school of cosmology, there was “ylem”*: a featureless mass of protons and neutrons containing all the matter in the universe. A little later (perhaps during the second microsecond of Creation), a “great event” took place. The ylem exploded with enough force to toss most of its matter a billion light years away. During the early moments of the resulting confusion, the protons and neutrons reorganized themselves into the chemical elements that form the present-day universe.

Cosmologists, of course, do not know that there was ever any such thing as ylem. What they do know with fair certainty is that the relative abundance of the chemical elements is much the same throughout the universe. Hydrogen is commonest. Except in odd corners like the earth, the heavier elements such as iron, lead, uranium, etc. are extremely scarce.

Since this is the case, argue cosmologists led by Dr. George Gamow of George Washington University, all the elements must have originated just after the great event when the ylem exploded. In the March Johns Hopkins Magazine, two cosmologists of the Gamow school, Drs. Ralph A. Alpher and Robert C. Herman, tell how they think the elements were formed.

First Seconds. A few hundred seconds after the great event, say Alpher & Herman, when the universe was filled with a gas made of protons, neutrons and smaller sub-atomic particles, its temperature was about i billion degrees, and through it shot violent gamma rays. At this point, the collisions among the particles and gamma rays were too powerful to allow any of the particles to join together into atomic nuclei.

Under the Alpher-Herman hypothesis, the gas, constantly expanding, soon cooled enough to allow an occasional proton to join with a neutron, forming the two-part nucleus of heavy hydrogen. Then, little by little, larger nuclei were formed, such as lithium, boron and carbon. Most of the nuclei grew by capturing more neutrons. When they captured too many, they became unstable. Then some of the neutrons inside them turned into protons and electrons. The electrons shot off as high-energy beta particles.

No More Neutrons. This process of “beta-decay” made the nuclei more stable —able to capture more neutrons. Bigger & bigger they grew, until all the elements in the universe had been formed. Then this growing process stopped; there were no more free neutrons, and the gas had become too cool to support nuclear reactions. Drs. Alpher & Herman believe that all the elements were formed in less than an hour after the great event.

The Gamow theory collides sharply -with that of British Cosmologists Hoyle and Lyttleton (TIME, Nov. 20), who believe that matter in a constantly expanding universe is being “created” continuously in the form of hydrogen, which gradually turns into heavier elements in the hot hearts of stars. Followers of Gamow agree that the universe is still expanding, as a result of the original explosion of the ylem. What they find harder to explain is why the earth should happen to be at the exact center of the great expansion.

* From the Greek word for wood or matter.