The author, Lawrence Cave, points out the difference between observable facts – things that can be proved beyond doubt – and theories, which are based on a set of assumptions. These need to be tried and tested before they can be shown to be true. In his article, he examines a scientific theory which is often spoken about as though it were indisputable fact. Is the "Big Bang" a fact or is it just a theory?

Fact 1

When people use modern telescopes to look at distant galaxies they find that the light looks slightly different from sunlight. The simplest way we can describe this difference is to say that the light from distant galaxies looks slightly red. Hence this observation is known as the “red shift”.

Fact 2

When we look out into outer space using a telescope which is already in space, we detect radiation known as cosmic microwave background radiation.

Fact 3

This fact involves the elements in the universe – things like hydrogen and helium, oxygen, nitrogen, carbon and so on. Scientists have noticed that the universe contains mainly elements that are light in weight. The lightest elements, hydrogen and helium, are by far the most common elements in the detectable universe.

Fact 4

The fourth fact that is often mentioned is that galaxies seem evenly spread through space. It does not matter in which direction we look, the spread of galaxies looks basically the same. These are the four observable facts on which the “Big Bang” theory is based.

The Development of the “Big Bang” theory

It was the first of these observable facts that originally made scientists develop the “Big Bang” theory. Scientists believe that the “red shift” in light coming from space indicates that the light source is moving away from us. This would mean that the universe is expanding. The other observable facts we have looked at are also consistent with the idea that the universe started with an explosion and is expanding in all directions.

1. The background radiation that we detect is considered to be the remains of the “Big Bang” explosion. 
2. The “Big Bang” theory predicts that the lightest elements would be produced first, the heavier elements being built up from them.
3. Scientists also realised that the galaxies will be evenly distributed through space if the universe is expanding in all directions following the “Big Bang”.

Scientists then make the following assumptions:

1. Nothing has ever happened to change the physical laws that we know today.
2. These laws are consistent and the same throughout the whole of the universe.
3. The red shift is caused by the light source moving away from us.

Using these three assumptions, together with our four observable facts, it becomes obvious that if our universe is expanding, then, if we roll back time, everything can be traced back to a single point in space time from which it all started. And that is what is called the “Big Bang”.

The “Big Bang” – fact or theory?

We must remember that this theory is based on what we can see today. No one knows what information modern telescopes would have given us thousands or millions of years ago. We must also remember that we cannot do any experiments to prove that the red shift is caused by the light source moving away from us. Notice that, contrary to the impression you may already have, there are not many facts that support the “Big Bang” theory. The few facts we do have support the theory if we accept the assumptions that we cannot prove.

Scientists are doing their best with the available information but they are almost certainly missing some important information. The “Big Bang” must remain an interesting theory, and cannot be regarded as a fact.

- Lawrence Cave

This article first appeared in the "Glad Tidings Magazine". Go to the Glad Tidings website to read colourful and instructive articles about the Bible:https://gladtidingsmagazine.org/