From Gareth Roberts
In his feature, “The universe before ours”, David Shiga suggests that one day we may be able to answer the question “why is there anything at all instead of nothing?” (28 April, p 28). This is more than optimistic: the question is a priori unanswerable.
By definition, there cannot have been anything before everything that is, and there cannot be anything outside it or after it. Calculating the probability of there being something rather than nothing at all is pointless, because this is beyond probability. There just is something rather than nothing, and there can be no deeper answer than that.
From Peter White
You mention the issue of whether time is infinite or whether it has a beginning and an end. These possibilities both assume that the structure of time is analogous to a straight line. There is another possibility, that time might have a structure analogous to a loop: everything happens only once, but time is not infinite and has no beginning or end.
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One model of the universe with which this would be compatible is one in which the expansion phase after the big bang is followed by a contraction phase leading to a big crunch. The singularity at the big crunch would not be similar to the singularity at the big bang; it would be the same one.
Time has a loop structure, and the singularity is just another point on the loop. I don’t know whether this is compatible with any of the models discussed, but it is at least a logical possibility and a way out of the dilemma.
Cardiff, UK
From Andy Howe
The feature reminded me of an essay by Roger Penrose over 20 years ago. According to the “strong” anthropic principle, the universe is the way it is because it needs to be observed by some self-aware life form. Penrose applied this argument to humans, explaining that the universe did not have to develop this way just to create the likes of us.
Noting that an uninhabitable universe of black holes is far more likely than one suitable for us, Penrose said: “The cheapest way of making a roomful of people, or even a world full of people, is by random selection…a statistical fluctuation, if you like, in an otherwise high-entropy universe.” Expand Penrose’s “world full of people” right up to the observable universe, and what you get is perhaps what the “black hole sea” model discussed in the feature is actually describing.
Sheffield, UK
From Paul Robinson
Am I missing something here? Isn’t asking what happened before the big bang rather like asking what conditions are like 25,000 kilometres below the Earth’s surface?
London, UK
Edinburgh, UK
