There is no doubt that our universe is expanding, and there is abundant evidence that it began in a primeval explosion of matter-energy – the Big Bang. With or without a Big Bang, there are two, and only two, possibilities for its future. The first and current front-runner amongst cosmologists, is that the universe is infinite – it will go on expanding forever, whether by the accelerating process currently believed or by some other process as yet unknown.  The second possibility is that in billions of years, under the influence of the gravity of all the matter-energy in the universe, the expansion will reverse and slowly but surely collapse into a Big Crunch. Whatever the details, there are just two options for the universe – infinity or ziltch!

In the first scenario, the very nature of a truly infinite universe is that anything that can happen, must happen, so our universe must eventually repeat itself precisely with an absolutely identical history by the process of ‘Poincaré recurrence’ (remember monkeys, typewriters and Shakespeare sonnets?). This means that since we are part of the events making up the history of this universe we must also be in the identical future universe. An analysis of what makes us feel like ‘us’ shows that this future identical ‘we’ must be, and more importantly must feel like, the ‘we’ who are writing and reading this. The billions of years between our death in this life and our birth in an identical future life will, for us, not exist because time is only detectable when we are alive to detect it. The upshot of this is that the instant we die we are reborn again in our mothers’ arms - in the ‘next’ life.

But a repeat of our universe also has implications for the nature of time, because if there is a future universe with a history absolutely identical in every detail to our universe, it must, by the principle of identity, be considered as our universe, repeated. The universe has returned to its starting point, and the dimension of time in which it has done so therefore must be considered as circular. So when we are reborn as ourselves, it will actually be in the repeat cycle of our universe in this circular dimension of time.

The second possibility, that the universe collapses into a Big Crunch, appears so different from the first that it might be expected to have a very different outcome. In fact the outcome is precisely the same for us and for time as for the infinite universe. It has been shown that all the matter-energy produced in the Big Bang could have been produced from nothing at all because the positive matter-energy produced is exactly equal to the negative gravitational energy of the matter-energy created and blown apart. The positive matter-energy has been created from an equal ‘debt’ of negative gravitational energy just as money can be ‘created’ by borrowing, and creating an equal amount of debt. This means that not only at the Big Bang but throughout its subsequent life – expansion and collapse - the total energy of the universe – positive matter-energy plus negative gravitational energy – remains zero.

At the Big Crunch the ‘debt’ will be ‘repaid’ with the positive matter-energy and negative gravitational energy cancelling out and the whole universe disappearing to nothing once more. And nothing really means absolute nothing – no space as well as matter-energy. The application of the principle of identity is now even easier. The Big Bang and Big Crunch are perfectly identical because their nothing-ness leaves absolutely nothing by which they can be distinguished! They, therefore, even more clearly than identical universes, can be considered one and the same event. When the universe collapses into the Big Crunch it has returned to the Big Bang, for the universe to begin all over again. So in this scenario, too, the dimension of time becomes circular.