Keith Ward / cosmology

- in the movie Timeline Gerard Butler and friends didn't time travel back to the medieval past, but instead traveled to another universe in the multiverse

A fan of science fiction, I have somewhat limited understanding of the multiverse (the hypothetical set of multiple possible universes that together comprise all of reality), but here's what Professor Keith Ward DD FBA writes of it in this excerpt from his Gresham lecture, Cosmology and creation ......

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THE MULTIVERSE

Some of the possible states it contemplates will be universes that can provide additional objects for its contemplation that have an independent reality that is not just in the divine imagination. If they are actualised, they will become what Newton called ‘sensoria of God’, logical spaces in which beautiful and intelligible objects of direct divine knowledge are given actuality, moving from the realm of the possible into the objective existence of the actual, and then being received back into the eternal through divine knowledge of them as actual.

How many such possible worlds are there, and how many of them may become actual? We have seen that in modern cosmology the idea of a ‘multiverse’ is often thought to be the most plausible explanation of the fine-tuning of this universe. When Martin Rees, the British Astronomer Royal, in his book ‘Our Cosmic Habitat’ (Princeton University Press, 2001), considers the amazing fine-tuning of our universe, he says, ‘We seem to have three choices: we can dismiss it as happenstance, we can acclaim it as the workings of providence, or (my preference) we can conjecture that our universe is a specially favored domain in a still vaster multiverse’ (p. 162).

A multiverse is a vast – but how vast? – ensemble of universes, of spacetimes, that all exist. Perhaps black holes can spawn other spacetimes, with differing initial conditions and laws of physics. We could never communicate with such other universes. But it we had a vast range of them, perhaps every possible set of laws and initial conditions, then the existence of this fine-tuned universe would no longer be a surprise. It would be bound to happen sooner or later.

Appeal to a multiverse, within which our universe is just one case, still leaves massive problems unsolved. What is supposed to specify the array of possible laws and conditions from which particular existent universes arise? How many arrays are there, and in what sense do they exist as possibilities? What can ensure that every possible universe actually comes to exist, that the whole gamut of possibilities is systematically run through? And is it really the case that there is a finite set of universes, all of which will come to exist sooner or later (for if the set of universes is infinite, they will never all exist)?

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