Science: Non-Commonsense Cosmos

How did the universe get the way it is? This largest of science’s questions was attacked with vigor by the bold “Cambridge cosmologists” at the Oxford convention of the British Association for the Advancement of Science.

In reasoning about the universe, said Cosmologist Thomas Gold, “we must be on our guard against that evil intruder ‘common sense.’ ” Common sense, Gold pointed out, is derived from human experience with objects of moderate size such as the human body and the solar system. Scientists now know that very small objects (i.e., subatomic particles) behave in a non-commonsensical way. Very large objects may behave unreasonably too.

Unnatural Laws. The things that science deals with, said Gold, range in size from electrons (radius 10 -13 cm) to the universe itself (radius 10 27 cm). Man, the earth and the solar system lie midway between the two extremes, and the laws that govern them have become so familiar that any deviation seems wrong. But gravitation, one ruling common-sense force, is ignored by subatomic particles, which are attracted to one another by enormously strong forces effective only at very short distances. To explain events in the “microphysical” world, scientists need the “unnatural” rules of quantum theory.

In the same way, Gold reasoned, the “megaphysical” world (larger than galaxies) seems to have laws of its own. One of them is the mysterious force that causes the universe to expand, the galaxies fleeing from one another instead of being drawn together by gravitation. There may be many outlandish laws.

It will not be easy, said Gold, for scientists to discover the megaphysical laws; they cannot play with galaxies as they do with neutrons and electrons. But all sorts of clues must be lying around, and they should be spotted eventually.

The ancient Greeks, said Gold, were in rather the same fix when they tried to determine the shape of the earth. They could not see the earth as a whole and the details that they could see were confusingly irregular. But they fitted clues together and eventually decided (against common sense) that the earth is round.

Explosive Model. Cosmologists believe that the best way to study the universe is to set up a theoretical “model” of it and then find out by observation whether the model matches the real universe. Cambridge Cosmologist Dennis W. Sciama explained that since the megaphysical laws are largely unknown, cosmologists must test their models against the few facts they do possess. One set of facts they are reasonably sure of: the universe “is made of a fairly uniform mixture of chemical elements; 95% is hydrogen, nearly 5% is helium formed in stars. The small remainder is the heavier elements from lithium to uranium. The elements get scarcer as they get heavier until they reach the atomic weight of 100; after that, their abundance is about the same.*

A respectable model of the universe must explain successfully this relative abundance of the elements. One theory, the “evolving universe” (held by George Gamow and Ralph Alpher), presumes that about 5 billion years ago the universe started life with the great-great-grandfather of all explosions. The universe was then small, dense and hot, and was made up entirely of radiation and neutrons. As it exploded and expanded, most of the neutrons split into protons and electrons (hydrogen). A few joined together to form the heavier elements. It was all over in about 15 minutes; since then, the abundance of heavier elements has remained about the same.

Continuous Creation. The Cambridge cosmographers do not favor the theory of the explosive universe. Sciama admitted that the heat of the original explosion might permit a few elements to form, but he said that according to the principles of nuclear physics the building-up process would stop with helium. An even worse flaw, said Sciama, in the explosive universe theory is that it presupposes a complicated set of original conditions (temperature, density, etc.) that its proponents believe would have produced the existing universe. This is as arbitrary, said Sciama, as saying: “Things are as they are because they were as they were.”

The Cambridge cosmic model is the “steady state universe” featuring the startling principle of “continuous creation” (TIME, Nov. 20, 1950). In each several million cubic feet of space, it teaches, one atom of hydrogen is created every year. Some act of creation is unavoidable, say the Cambridge men (because the universe exists); their single assumption is much less arbitrary than assuming the creation of the whole universe jammed tightly and hotly together.

Out of the created hydrogen atoms, says the steady state theory, the whole universe has developed. Pulled by gravitation, the hydrogen atoms clot together, forming gas clouds, stars and galaxies. The galaxies flee from one another after their own odd custom, and more hydrogen is created in the space vacated. The process continues forever without beginning or end.

Supernovae Impurities. When this model was first propounded, it was largely theoretical. Now, said Sciama, it is being checked against the abundances of the elements, the same set of cosmic facts that is the principal support of the explosive universe theory. Some stars made of hydrogen explode as supernovae. Their temperature and density are known roughly from observation, and they are high enough to make hydrogen atoms join together, forming all the heavier elements in about the right proportion. The explosion distributes them throughout the galaxy, and supernovae are frequent enough to supply all the heavy-element “impurities” that a typical galaxy possesses.

Much more checking will have to be done before all cosmologists agree that the universe is in a steady state of continuous creation. But Sciama believes that a good beginning has been made toward proving by observation that all the properties of the universe grow naturally out of new hydrogen created in empty space.

*Cosmologists consider the earth a non-typical speck of heavy-element impurities.