how did the universe start?

what science says

Fifty years ago, many scientists thought it possible that the universe had always existed. The two main theories were "steady state" (the continual creation of matter at the centre of an expanding universe so the universe appears the same for all time) and "pulsating" (the universe goes through regular cycles of expansion and contraction for all time).

However these theories are no longer believed by most scientists, and it is generally considered "proven" that the universe began about 15 billion years ago with the "big bang".

In the big bang, matter, energy, space and time were created in an instant. Initially concentrated in an infinitely small point called a "singularity", the universe expanded outwards rapidly with enormous energy. This was not like an explosion into empty space, but expansion of space itself.

In the first fractions of a second, when current laws of physics did not apply, particles began to form out of the enormous energy - first small particles like quarks, gluons and leptons, later the more familiar protons, neutrons and electrons. The four fundamental forces or interactions (gravity, electromagnetism, the strong nuclear force and the weak nuclear force) developed gradually, because scientists believe that these forces are actually caused by an exchange of very small particles (bosons). At this stage the universe was so small that there was no space for more than minor irregularities, which was important for the later structure of the universe.

As the age of the universe moved beyond seconds to minutes, and it grew in size to about 10 ¹⁵ kilometres across, nuclear fusion formed the first of the nuclei we know about today - Hydrogen and Helium - in proportions that proved necessary for the universe as we know it to form. The universe was still incredibly hot.

After several hundred thousand years, conditions had stabilised enough for the first atoms to form; after several hundred million years, the first stars, and later the first galaxies, began to form by gravitational attraction. Supernova stars created many of the heavier elements out of the lighter elements, and then exploded them out into space, making them available for planets which later formed, thus allowing the complexity of chemistry on earth necessary for life.

The universe is still expanding today, and scientists are able to (a) extrapolate backwards and describe the early moments of the big bang mathematically, (b) predict outcomes of their theory which can be verified by observation of the universe, and (c) show mathematically that the alternative theories have significant flaws, thus demonstrating that the big bang origin is almost certain.

is there a scientific explanation, was it god, or what?

Logically, there are three possibilities for the cause of the big bang:

1. the universe has always existed;
2. something caused it; or
3. nothing caused it but it began anyway.

Option 1, with the corollary that something that has always existed doesn't need a cause, was once a popular choice. But the demise of the steady state theory of the universe and the almost universal acceptance of the big bang virtually rule this out.

Option 2 seems to be the most obvious choice. For most people, this implies a god of some sort, but some believe our universe could have resulted from a previous universe. This logically leads to the conclusion that there has been an infinite series of universes.

Option 3 seems to go against common sense, but is nevertheless accepted by many people, especially scientists who avoid "supernatural" explanations.

So we have three main options. Either (i) a powerful god, who has always existed and therefore doesn't have or need a cause, created the universe for some purpose, or (ii) there has been an eternal succession of universes giving birth to later universes, or (iii) there is no god, matter is all there is, and for reasons we are unable to explain, and probably never will, the universe appeared at the big bang. All three may seem unlikely, but the universe is here, so one of them must most likely be true.

All views have their supporters, but none can be proven or disproven. Each of us can decide. I believe in God - what do you think?

Let us know what you think, agree or disagree, or ask a question on the forum, or send an email - we'd love get feedback.

For more information, see the universe (does there have to be a reason for everything?). You can also check out some references for further reading.

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