LETTER:The Big Bang and why our universe may not be alone

Sir: Infinity is hard to visualise, but impossible to deny. In infinite space-time, our universe, all 1.5bn light-years of it is, in human terms, less than a speck of dust existing for the blink of an eye. It is improbable - to me, inconceivable - that space-time was empty until the Big Bang happened and that our universe is its sole occupant. If conditions were right for the Bang to happen at one instant of space-time, the probability must be high that it was also right at other spaces and times. Infinite space-time should be littered with the results of other Big Bangs. If so, where is the evidence?

One possibility is that space-time has been filled with matter of the kind that wakes up our universe. One can visualise a random soup; but in such a soup, gravitational forces would cause matter to aggregate and then coalesce as in black holes. Further aggregation could result in gravitational collapse, leaving a zone with very little matter remaining free within its sphere of influence. If the enormous energy were then to be released in a Big Bang, a universe would be created.

If infinite space-time is filled with matter which is in a ferment of gravitational motion, it would be nice to postulate universes of matter and anti-matter in roughly equal numbers in collapsing and expanding modes. We may be seeing the first signs of such things in the Hubble observations of outer space.

Prof D M M McDowell

Brighton, East Sussex

The writer is Emeritus Professor of Civil Engineering, Manchester University.