Astronomer Royal Sir Martin Rees explores one of the great questions facing science - Are We Real?

Chat Ed : Welcome to this evening's What We Still Don't Know chat with Astronomer Royal, Sir Martin Rees! There is a fundamental chasm in our understanding of ourselves, the universe, and everything. To solve this, Sir Martin takes us on a mind-boggling journey through multiple universes to post-biological life. On the way we learn of the disturbing possibility that we could be the product of someone else’s experiment.

Sir Martin Rees : Good evening everyone, I hope you end up confused on a higher level than before after watching these programmes.

Gus : Good evening to you

lonelymuppet : many years ago we split religion/belief and science apart. are we now beginning to merge these two back together?

a : What is your personal religious view?

Sir Martin Rees : I think science makes us aware of the wonder and mystery of the universe, which is an important part of religion. I have no dogmatic views, but I value participating in religious services.

Cpt Oblivion : right first off do we live in a computer game antiquark : Hi Sir Martin, can we not use occams razor to deal with whether we are a simulation or not?

Sir Martin Rees : I don't know, but what is amazing is to realise that we can't rule that out completely. It's not clear what we would then conclude and in any case I don't see why we should be adverse to a complex and extravagant universe. It's clear that there are many more planets than were needed for our existence, so why not more big bangs as well?

Hamish and James : How do we differentiate 'what we do not know' from 'what we cannot know'?

Sir Martin Rees : There are many things which we don't yet know but the interesting distinction is between mysteries we may one day solve and those which are far beyond the capacity of human brains. Science is still just beginning.

col : Rather than a multi-verse, has it been considered that our laws of nature could be the result of the evolution of a history of universes and that a natural selection of laws has been the 'tuning force' behind our fined tuned laws of nature?

Tim B : Why do you think a designing intelligence must be external to our universe? Might we not have a self-organising universe?

Sir Martin Rees : That idea has been discussed, col. But we would still need to know what force drove the selection. Tim, we might... but we see no evidence of very advanced technology elsewhere in our universe and that makes me sceptical.

Robbie : It's phenomenal what cosmologists and scientists are discovering, I have the utmost respect for you all :-)

PotentialCosmologist : Do you think it possible that WE are designing our universe as we go along?

Sir Martin Rees : I don't think so because if we were we wouldn't so often get it wrong.

ynotmain : this programme is messing with my head tonight...........

Ian : These minor calculations mentioned in the program, that, if minutely different, would not allow life to evolve, is that life as it is now, or would evolution just have taken a different course and ended up somewhere else with a different end result, a different species?

Sparrow : If the rules of the Universe were slightly different, wouldn't something else have evolved instead. In other words, have we not evolved around the rules of the universe?

Sir Martin Rees : No, Ian, if there were for instance no atoms apart from hydrogen or no long-lived stars, then one cannot imagine any complex evolution and the universe would be sterile. Ditto if the universe collapsed after only a short time. We can imagine laws that would not allow anything complicated to emerge - there might, for instance, be only one kind of atom or no stars or only dark matter, or no force of gravity, or only two dimensions and there could then be no complexity.

paulrowland : what is consciousness

avalon : do you believe that we have a spirit???

dave : does all this thought drive you insane?

Sir Martin Rees : Consciousness is the deepest mystery of all. We believe we have a spirit but how it emerged is beyond our understanding. I think I'm sane, but I'm not sure my friends agree, dave.

fulanito_chile : Sir Martin what do you think happens after you die?

frazer : do you think it will be possible to bring back the 'soul' of dead people with technology, do our bodies matter, can our consciousness exist outside death?

Sir Martin Rees : I don't believe it, but we cannot be sure. I don't think it's worth freezing my body in the hope of being revived later since even if it were possible I can't see why anyone would bother to revive me.

iamark : Could our consciousness be connected to the infinite size of the universe?

Streety : Re a multiverse and our 'spirit' or 'soul', could it be supposed that death leads to another universe?

Sir Martin Rees : It looks as though consciousness is something that emerges in complex networks of nerves and is therefore probably localised. Streety, it would be nice to think that but I suspect that our personality is so closely linked to our bodies and brains that nothing specific of us will survive.

michael howarth : could there ever be anything outside the multiverse?

Ang25 : If we are taking things to the extreme and proposing Multiverse theory...is it not too broad a leap to suggest that these could each also belong to clusters on an ever-expanding escalator of infiniverses?

Sir Martin Rees : It is possible, but it is a question of definition. I would define a multiverse as including ALL the universes that are part of physical reality. There may be an infinite number.

Gerald : Sir Martin.....So Its Turtles all the way down!!

Sir Martin Rees : Heh, it is true that every question opens up a new mystery when we answer it. At some stage we always have to say that things are as they are because they were as they were.

lonelymuppet : would it not be possible to create a version of the 'life' game which we could leave to evolve into a thinking being as such?

Sir Martin Rees : That is a fascinating question and we cannot absolutely say it is impossible, but it would demand an absolutely vast chequer board.

Andrew : Is this wonderful series going to be repeated? If so when? Or can I buy it on DVD?

Sir Martin Rees : I don't know, but I hope you will persuade Channel 4 to consider this.

Richard J K : I was hoping that you would have commented more about dark matter and dark energy zoidberg : dark matter scares me! i don't like the thought of it floating through me!

Sir Martin Rees : There was some of this in the second programme but when dark matter particles go through you you don't feel a thing.

Chris31 : Why do scientists shrink at the idea of a designer? Nigel A : Creationism, Atheism or Simulationism - which would you prefer for basis of reality?

Sir Martin Rees : Not all of them do Chris, but I think we should seek to explain as much as we can without that hypothesis. I don't like any of them much, Nigel, but I believe we are part of some marvellous evolutionary process which still has a long way to go beyond the human stage, here on earth and far beyond.

VX : Do you have any theories as to why we are so concerned with why almost everyone in the world wants to know how the universe came about

Sir Martin Rees : Humans are curious about origins and that's why the origin of life and of atoms and of the universe fascinates so many. Children are keen on dinosaurs and space, despite their lack of relevance and adults are just as curious.

Robbie : Sir Martin, what is the universe expanding into?

Sir Martin Rees : It would take too long to answer that clearly, so please read my book 'Cosmic Habitat'.

Chris31 : I know personal opinions are personal .... but, after watching the program I was still left none the wiser about our origin. It was all very good science and all but this has been going for so long when are we going to get to the bottom of it?

Bongadoo : Do you think a universal theory of everything is ever achievable? nate : nice plug

Sir Martin Rees : We'll never get completely to the bottom but I think there are some questions which have baffled our predecessors which are now settled, such as the size and shape of our universe and the way stars, galaxies and planets evolve in it. But we are only just beginning. Remember that scientists can't even agree on things like diet and childcare, so be patient!

BenJC : What other reading material is there around the issues the series covered?

Sir Martin Rees : I'd recommend three of my books called, 'Just Six Numbers', 'Our Cosmic Habitat' and 'Our Final Century'.

peterbennett : Sir Martin - what shape is our universe? I never got this.

GODlike : its doughnut

Chat Ed : mmm

Sir Martin Rees : It is symmetrical and almost completely smooth, but with so-called ripples imprinted in the big bang, which develop into galaxies and larger cosmic structures.

nai : sir martin rees is scaring me he knows to much

Ramish : If we were able to become silicon people, then we wouldn't need to reproduce would we?

Sir Martin Rees : Ramish - I think that is one of the many disadvantages of being downloaded into a computer.

metafizzick : Are theoretical physicists now on a collision course with metaphysics?

Sir Martin Rees : meta - I don't think so but there is some territory which they should realise they share.

ab : How do I know that you are talking to me?

Sir Martin Rees : Heh.. that is a deep philosophical question ab, you know you are hearing me but you could of course be, what philosophers call , a “brain in a vat”, receiving signals via your nerves which don't correspond to an external reality like me.

peterthegeologist : What experiment would you most like to see performed, money no object, that you think would help to answer fundamental questions in cosmology?

Sir Martin Rees : I'd be more modest and try to understand the origin of planets and life, because I really believe that exobiology is a great science for the 21st century.

Elliot : What research are you working on right now?

Sir Martin Rees : I'm trying to understand how the first stars and galaxies formed after the big bang and how black holes form.

neo : what do you think the future will hold for humans

liz : How do you think we might evolve?

Sir Martin Rees : In my off-duty moments I speculate about multiverses and extra-terrestrial life. I think this century will be a dangerous one but beyond that time humans may live not just on earth, but out in space. The ones in space will use genetic engineering to quickly modify themselves into new post-human species better adapted to an alien habitat.

ashchap : do you ever get depressed and think 'what’s the point'

Sir Martin Rees : ashchap - things that depress me are everyday things and wondering about the cosmos tends to cheer me up rather than otherwise.

Chat Ed : I would love to keep him chained to chat for many more hours, but time is up... for us at least.

Sir Martin Rees : This series tried to focus on the big questions, not just because they are important but because the experts are just as confused as everyone else so there is not as big a gap between specialists and the average viewer as there would be if the focus had been on more specific technical issues. But even though the ideas are fascinating what leads to progress in science is always new experiments and technology - armchair theorising by itself won't find the answers. So we hope for better experiments and more advanced technology. Thank you for your questions and goodbye.

alien_nation : thanks sir martin really good show thanks

Silv3r : thanks for opening our minds to other concepts

karen : Thanks Sir Martin

Fred Robinson : Yes - well done.

blackcurrant : Thankyou

Greg : thanks for a great series!!!

Adam : Thankyou Sir Martin

ollywass : keep it up

MrClarinet : Thanks Sir Martin, everyone here enjoyed it (including my Granddad)

Arf : thx sir martin.

voodoo : Pleasant dreams!

dna : good programme, thanks

Sir Martin Rees leaves the room