Navigation Menu+

Compendium of Reason Physics Q & A

One of the many highlights of 2014’s Brian Cox and Robin Ince’s Christmas Compendium of Reason shows that took place at the Hammersmith Apollo was the live Question and Answer sessions that opened the second act.  Audience members tweeted in questions for the panel during the interval and then a select few were answered on stage.  This recording is taken from the second night on Friday 19th December.  The panel was chaired by Robin Ince and featured particle physicist Professor Brian Cox, theoretical physicist Professor Jim Al-Khalili, astronomer and The Sky at Night co-host Dr Chris Lintott and planetary scientist Professor Carolyn Porco.  The session began with an on-screen appearance from the Robin and Brian puppets and Robin making fun of Brian while Brian stood backstage…

Please note that the following clip contains some explicit language and may not be suitable for young children.

Can you just gaze up at the sky and point at a thing?


Robin - We now are going to find out from those physicists, please welcome Brian Cox, Carolyn Porco, Chris Lintott and Jim Al-Khalili!

Brian - It’s so frustrating to have to sit there behind this curtain unable to answer this gibbering maniac.

Robin - These are their questions Brian: question number one, which I think shows how deep their learning and knowledge of physics has become since watching your programmes, question number one from Helen is, can you just gaze up at the sky and point at a thing? So thank you for that, Helen White.

Brian [to Chris] - You’re also an astronomer.

Chris - I’ve always wanted to know how this is done.

Brian - This is Sky at Night versus Wonders of the Solar System face off -  pointing face off.

Robin - This is going to look like Saturday Night Fever!

Carolyn - What are you doing? 

Brian - We’re going to point at the sky!

They point at the sky to much applause.

Robin – Well, that’s that.  The next one is, ‘Do you think the double-slit theory of light proves that all is pre-determined and all decisions are inevitably pointless?’  You can see how I segued from this to…so, ah, who wants to start?  Jim, I’ll start with you.  So the double-slit experiment, the idea of pre-determination, all decisions are ultimately pointless, you’ve been kind of dealing with this currently on your BBC2 show, or BBC 4 show, is it both, I don’t know, anyway, well in one world it will be, so, um, what do we reckon?

Jim - If you follow the multiverse interpretation of quantum mechanics, then the particle, rather than going through both slits, there are two universes, in one it goes through one, in the other universe it goes through the other, so all possibilities exist and everything is predetermined.  But, although I think Brian is quite keen on that interpretation, I’m not.  So I think there’s what’s called quantum indeterminism which means that everything is open and subject to chance and probability but I don’t think that affects our free will because we don’t have free will.  Well, we think we do but that’s just an illusion and that’s got nothing to do with quantum mechanics.

Brian - Happy Christmas!

Robin - But in another universe, Sad Christmas and in another one, F**king Christmas.  Well done, by the way, your swearing in your tweets has really improved, well done Professor Idle. Has anyone else, so, in terms of…what do you think, Brian?  Predetermination and free will.

Brian - So Jim’s right, there are two, there’s a few interpretations, quantum theory, well, the first thing to say is that it works so it’s our best description of nature, at all scales, at all levels, the only thing it doesn’t describe is gravity which is described by Einstein’s Theory of General Relativity which is a hundred years old next year, it’s its hundredth birthday in 2015, ah, so there’s no doubt the theory works as an accurate description of nature.  The problem is, exactly as Robin referred to in the question, how do you interpret the idea that it’s a probabilistic theory, basically.  So what the theory tells you is given a particle in some place, at a partiular time, or in some region of space, where is it likely to be at the next instant?  Is it likely to be here or here or here, and it gives you a beautiful prediction of the distribution of probabilities.  There might be a 50% chance it’ll be here and a 20% chance it’ll be here etc.  So, the thing is, how do you interpret that?  Because obviously when you make a measurement of the particle, it is somewhere.  So what happens?  What changes?  And that’s the thing.  So the many worlds interpretation, as Jim mentioned, is that actually all of those probabilities are real and there are essentially an infinite number of universes and in some of them, everything happens.  So that’s the many worlds interpretation.  The interpretation has problems because…

Chris - The problem is that it’s expensive!  You have to solve an infinite number of universes to solve a problem with your theory.  It’s just extravagant!

Brian - God doesn’t mind.

Carolyn - Don’t you have…

Brian – So, the point is, so the other idea is though, what does it mean it observe, you get into philosophical problems then as Jim…what does it mean?  Do I observe it?  Does it mean that conscious observers are special or does it mean… So there are problems with the interpretation and there’s no universal agreement, it’s fair to say.  The theory’s a hundred years old…

Jim - Yeah.  Quantum Theory is the strangest…it’s the most powerful theory in the whole of science but it’s the only theory in science that doesn’t have a unique explanation or interpretation.  It seems to have got away with it and that’s outrageous.

Carolyn - Well that’s what makes it powerful.

Jim - Well,  hmmm...  

Carolyn - It’s very flexible.

Jim - There’s no other theory in science…Einstein got given credit for the general…for the special theory of relativity, all the maths was already done, all he did was come up with an interpretation and explain it and he’s credited with it.  Quantum mechanics, all the maths is there, and we’ve got half a dozen interpretations and we don’t know which is the right one.

Brian - Did you just slag off Einstein?

Jim - Pardon?

Robin - Fight! Fight! Fight!  There is actually, one of the questions was, who would win in an arm wrestle, Jim Al-Khalili or Brian Cox.  You’ve [Brian] got more to lose if you get bruised.

Carolyn - Am I allowed to ask a question?

Robin - Carolyn, yes.

Carolyn - I want to ask a question.  This multiverse idea is a little bit unsettling to me because it seems to violate energy. I mean, if you have an infinite number of universes you need an infinite amount of energy.  Right?

Brian – Well, not necessarily.  In, um, there’s a strange property of general relativity, this is Einstein’s theory of relativity, it says that space and time are curved by the presence of energy.  And you can arrange things such that, or things can be arranged that the energy in the curvature, the energy in the gradational field, if you like, exactly matches and balances and cancels out the energy in the matter and the energy in the universe.  So under specific circumstances you can have a zero energy universe existing where the energy in the field in spacetime is cancelled out by the energy in this stuff [taps the chair].  So it’s a free lunch, essentially.  You can have a free lunch .

Carolyn - I don’t know.  I think you did a little trick right there.  [Everyone laughs.]  You did …

Brian – No, it’s Einstein.  That bloke he doesn’t like!

Carolyn - No, you did a trick.  You did a trick because there’s mass in these universes and mass is energy.  You just did the normalisation and you made everything go to zero.

Brian - No, I’m just assuming it’s taken as read in this audience, that energy and mass are the same thing.  Everybody knows that E=MC² in this audience.  It’s the most educated audience…

Carolyn - OK.

Robin - Every time we do one of these…Thirty years ago David Bowie was on this stage retiring Ziggy Stardust.  Now, Brian, tell me more about quantum mechanics!  Ah …

Brian - This is good, isn’t it?  We should give ourselves a round of applause!  Christmas quantum mechanics!  Brilliant.

Robin - We’ve only got four minutes left so Carolyn, and I’ll ask this to you as well Chris, if all the space agencies gathered together and pooled all their finances together, where should we be going next?  That is the question.  If there was one place to go, where should human beings be going next?

Carolyn - OK, I think everyone knows what I would be saying about this!  I think the most pressing question is, the most interesting question is whether or not life has gotten started elsewhere.  And we have places in our solar system that are really promising to go look, and the most promising place is that little moon I spoke about and that is Enceladus.  Why is it promising?  Because it’s ocean, which we know is laced with organic material.  It’s salty, which means it’s in contact with its core.  That’s starting to sound like our ocean, it’s starting to sound like it’s got all the hallmarks of places that we have been saying for decades now are habitable zones and we should go and investigate whether life had gotten started there.  On Enceladus that ocean is gushing into space.  OK, and all you have to do, I’m very fond of saying this, I’ve said this many times, all you have to do is land on the surface, look up and stick your tongue out and you’ve got what you came for because that stuff is, you know, gushing up, and 90 - 96% of it comes down and snows back down on the surface.  So it’s trivial to go sample it.

On places like Mars, they’re digging, they’re digging, they’re always finding water, water was there, but nothing yet …

Carolyn is interrupted by a weird cross channel in the theatre’s speakers.

Robin - Oh, that’ll be the CIA.

Carolyn - Somebody doesn’t like my answer!

Chris - I thought that was first contact!  But look, this is nice, but it’s all very parochial.  That’s like sitting here and deciding where we’re going to explore on the Earth.  We’re going to go to Clapham.  You know, this is local stuff.  I’ve nothing against Clapham.  Um, but, I’ve misjudged this audience.  Never mind.  I want us to be an interstellar species and I think we can make a start at that now for fairly small amounts of money. We know that there are planets around most of the stars in the galaxy, we didn’t know that a few years ago.  And we know how to launch a probe to one of those systems.  Now it wouldn’t be a very special probe.  It’s essentially a webcam with a slow motor but it would get us there in about 150 years.  And I think it would be good for us to know that there’s an experiment going on that would take 150 years…

Carolyn - Where are you going to?

Chris - Sorry?

Carolyn - Where are you going?

Chris - Oh I was going to…Proxima Centauri’s looking a bit dodgy, but there are four or five stars with exoplanets within ten light years or so, so you can get there on century timescales for not much money.

Carolyn - OK, well I want to be alive…

Chris - We should do both.

Carolyn - …I want to be alive when this happens.

Chris – Yeah, but it’d be good for us to know that right?  

Carloyn - OK.

Chris - To know that future…we’re going to launch an experiment that future generations get the results from.  And there is a catch by the way, we don’t know how to get this thing there so it can stop.  So it would go at an enormous velocity past these planets and send back about one picture.  But I think that would be a really fabulous picture!

Brian - It would be!  The ultimate cathedral really, isn’t it?

Chris - Yeah!

Brian - This is the ambition, to build this thing that will…

Chris - Exactly.

Brian - I see where I’m going there, that will essentially tell you nothing but…

Robin - Right, we’ve got three minutes so [we’re already well over time at this point…] this has been asked by about 17 different people.  Interstellar, what the f**k happened there?

Much laughter from all.

Robin - I’ve kind of condensed that into, ah, so who’d like to start on that one?  Jim?

Jim - OK.  So, ah, I enjoyed it.  The whole point of a science fiction movie is that it’s science f**king fiction!  Don’t take it seriously!  It bugs me!  Physicists say, ‘Ooh, it was wrong!’.  The person who was the consultant on Interstellar was a guy called Kip Thorne.  He was one of the leading experts on Einstein’s General Theory of Relativity.  He was the consultant, he was the guy who read Carl Sagan’s manuscript when he wrote the book Contact, he knows what he’s talking about.  Clearly the filmmakers took his advice and then ignored it in vast swathes of the film but, on the whole, I thought it was, well, actually, OK, no, there was a lot wrong with it…

Robin - Right.  No.  You’re rambling now.  Carolyn?

Carolyn - I enjoyed it too.  And let me just say Kip Thorne was also, as I was, a consultant on Contact.

Jim - You were as well?  I do apologise. 

Carolyn - No, no, no, I had nothing to do with wormholes or anything, I’m just saying he was more than…he did more than just read it, he was a consultant.  I don’t know enough about all this cosmology stuff to know exactly where they went wrong, but I enjoy pictures that depict a human future utilising space, being present in space.  So I even like Gravity, as silly as that was, with astronauts crashing into spacecraft and nothing happens to them, very unrealistic, but I enjoy seeing that kind of stuff.

Robin - Chris Hadfield was great, Chris Hadfield who was on this last year, he went, ‘the underwear we actually have in space is very different to what they wore in Gravity’.  A lot more absorbent and has various pipes.  So, um, Brian, how do you get away with dark energy, I mean those sums don’t add up.

Brian - Ah, they add up beautifully.  So I should just say, so dark energy is…the universe is observed to be accelerating in its expansion which is a thing which was unexpected, you would think that the universe is expanding but there’s matter and energy in it so they would be slowing the expansion down, but it’s speeding up.  And we know exactly how much of the energy of the universe is taken up doing that, it’s something like 68%, I think.  And one of the remarkable things is, if you add up all the energy in the universe, so the dark matter, and the dark energy and the matter and the radiation, everything, then you get a very specific number, Omega, which equals one.  So it’s a very specific, it’s one of the great mysteries, and the great questions…

Carolyn - That’s a normalisation.

Robin – Well, what a great hook.  We’re left with one of the great mysteries.  We’re going to have to come back and find out next year.

Brian - It’s very well proven.

Robin - It’s going to take longer than that.  So, we’ve run out of time.  Who would’ve imagined that twelve minutes isn’t long enough to cover all of physics?  So, thank you very much to all of our panel, a big round of applause!