There are two possible ideas about the origin of the universe. One is that it came into existence as the result of a creation event. This was dubbed “The Big Bang Theory” by an atheist cosmologist who disagreed with it. The alternative is the “Steady State Theory”, which asserts that the universe was not created, but has always existed and is thus eternal.
The evidence in favour of some version of the Big Bang Theory is very strong. It begins with the observation that the sky is dark at night, with a sprinkling of stars. In an infinite universe the sky would not be dark. No matter in what direction one looked, sooner or later the line of sight would end at a star, and the night sky would be as bright as the surface of a star. The fact that the night sky is dark shows that the universe is not infinite.
This is where gravity comes in. Because of gravity, a finite universe would be expected to collapse; the fact that it has not yet done so shows that the universe is not infinitely old. It must have had a moment of creation.
There is plenty of additional evidence for this. In 1915 the celebrated physicist Albert Einstein produced an equation which described the structure of the universe, which indicated that the universe must either be expanding or contracting. In the 1920s, observations of distant galaxies confirmed that the universe is expanding; if one ran the process backwards, this shows that at some time in the past the universe would have had no size at all, and before this it could not have existed. This conclusion was supported further when it was discovered that the abundance of hydrogen, helium and other light elements was what was predicted by the Big Bang Theory, and the discovery of the cosmic microwave background radiation put the matter beyond doubt. The universe had a beginning.
This conclusion was resisted by atheists for a considerable length of time. As one atheist put it, “Many people do not like the idea that time had a beginning; probably because it smacks of divine intervention.”* This opposition carried on into the 1990s, but effectively the fact that the universe came into existence at some moment in the past has been proved beyond reasonable doubt.
The Implications of the Big Bang
The important point is to think what this means. The fact that the universe came into existence means that there is a theoretical possibility that the universe would not exist.
All entities can be divided into two classes. There are entities which could be different from what they are; these are called “contingent entities”. A contingent entity requires some other entity (or entities) to explain why it is as it is. The other class of entities is those which can only be as they are: these must exist and cannot be different. Such entities are called “necessary entities”; they do not need any other entity to cause them or to explain why they are as they are.
It is possible that the universe could not exist. After all, there could have been a time before which the universe did not exist. Thus, the universe, and everything in it, is contingent. This means that it needs an entity outside itself to cause it, and to explain why it is as it is. If this entity is contingent, it requires another entity to cause it, and so on. In the end, the chain must stop at a necessary entity. This necessary entity must have properties which we would associate with God.
The entity is eternal, it needs no creator, it is immensely powerful, and there is no other entity which can limit it or change it. These are some of the attributes of God.
John Thorpe
* Stephen Hawking (1988): A Brief History of Time p. 46