Rees was interviewed for The Conversations Anthill podcaston Nothing.
This Q&A is based on an edited transcript of that interview.
Q: Is empty space really the same as nothing?
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A: Empty space seems to be nothing to us.
Likewise, empty space is conjectured to be quite complicated.
We know that the universe is very empty.
Moreover, weve learned that there is an exotic kind of energy in empty space itself.
They can even create a tiny force.
But what about empty space on large scales?
A: The fact that empty space exerts a large-scale force was discovered 20 years ago.
Astronomers found that the expansion of the universe was accelerating.
This was a surprise.
Indeed it determines our universes long term fate.
Q: But is there a limit to what we can know?
A: There are several theories that aim to understand this, the most famous beingstring theory.
But none of these theories have yet engaged with the real world so they are still untested speculation.
Time is like a fourth dimension.
But when you look closer, you see that one dimension was in fact three dimensions.
String theory involves complex mathematics so do the rival theories.
Q: Within our current understanding, how can we explain our entire universe expanding from nothing?
Could it really just start off from a bit of fluctuating vacuum energy?
That would happen at a time of about 10-44seconds whats called thePlanck time.
And there are many versions of a cyclic universe.
It was only 50 years ago that strong evidence for a Big Bang first emerged.
But there have ever since been speculations about whether this is just an episode in a cyclic universe.
I think we should explore them all.
Q: How will the universe end?
The particles in it may decay, making the dilution proceed indefinitely.
Q: How confident are you that science can ultimately crack what nothing is?
That is huge progress.
Then we may have to await the emergence of some kind of post-humans to get a fuller understanding.
Martin Rees, Emeritus Professor of Cosmology and Astrophysics,University of Cambridge.
This article was originally published onThe Conversation.
