It is impossible to know what existed before the Big Bang. The various theories are pure speculation — and since they cannot be tested or proven they are philosophy rather than science.

It is, of course, impossible to know what existed before the Big Bang. The various theories are pure speculation — and since they cannot be tested or proven they are philosophy rather than science.

Even though cosmologists can be fairly certain of events a few seconds after the Big Bang, they will probably never know what preceded it.

While most scientists agree that an unimaginably huge explosion “created the universe” somewhere between 13 billion and 20 billion years ago, there is no particular reason either to support or refute the idea that anything existed before it.

It is known to be expanding at a fantastic rate, and it therefore follows that billions of years ago it was far, far smaller.

In fact, it is believed that at the moment before the Big Bang the universe was infinitely small, with all the galaxies we now know massively condensed into a space tinier than a quark — the smallest particle of matter known to man.

The distance between two points was zero, as was the volume of the entire universe, while the density of matter was infinitely great.

Some believers in a finite universe think that this infinitesimally small state was reached after a “Big Crunch” during which the previous form of our universe contracted, with galaxies, stars and planets compacting with incredible violence and temperatures of billions of degrees.

They believe that may once again be the fate of our universe 30 billion years from now — and that the universe is “pulsating”, expanding and contracting every 80 billion years.

For the “Big Crunch” to happen again, though, the combined gravity of all the mass in the universe will have to overcome the speed at which the galaxies are expanding.

Other scientists, even those who believe in the closed universe, dismiss this theory, believing there is not enough mass to halt the expansion. Some experts believe the universe is infinite and will expand forever.

The fact is that the question of existence before the Big Bang may well be meaningless, because in trying to make sense of it the human mind is limited to concepts which the Big Bang actually created.

Our imaginations cannot cope without thinking of things in terms of space, time, gravity, energy and matter. And yet the chances are that, before the Big Bang, none of those existed.