 Hello, my name is Simon. I'm a professor of quantum technology here at the University of Oxford and I want to make a video not about quantum technology, although that is a cool topic and I would like to make some videos about it. This is a video about the movie Iron Man and whether the stuff we see happening in that movie, all the fantastic fight scenes and crazy stuff going on, is allowed by physics. Is it a yes or no from the point of view of physics? On whether we what we see happening could happen. I think it's quite interesting because it causes you to think about some of the physics and maybe the answers are a little bit surprising. I should say it's not my intention to upset anyone and spoil a movie for them. I really enjoy the movie. It's a great movie. So I'm not trying to spoil it I'm just trying to think about it But if you would rather just watch it without someone like me criticizing the science, then maybe don't watch this YouTube video I'm really not trying to, you know, start any fights here. I just want to enjoy thinking through the science. And what else to say? I think that it's a good movie to choose because Iron Man is a technology-based hero. All his abilities and powers are supposed to come from the technology that he has built and that is in our own near future. In fact, it's set in the now But it's a little bit more advanced than we have because we understand that Tony Stark, the guy who wears the suit in Iron Man, is a genius And so he is able to go a little bit further, a little bit deeper than the rest of us can and effectively bring tomorrow's technology into today But we're not talking about sort of Star Trek level technology and doing things that physics would consider or that our best understanding of physics says is impossible. It's just making, you know, 10 years time, perhaps, technology possible now. So I think that's why it's a really interesting one to choose. So what can we say about this checklist of abilities that the suit has from the point of view of physics? First, the toughness of the suit, its strength against impact I see no problem with that. Physics allows for super strong materials compared to the stuff that we have in everyday life. What about the physical strength that he has? Maybe 10 or 100 times stronger than a normal person. He's able to do some pretty amazing stuff I don't see a problem with that in the sense that you can certainly imagine lots of small powerful electric motors Which are woven close to the surface of the suit because it's quite, you know, type fitting really So that it boosts his own power. I don't see a problem with that What about the flight of the suit? Can he really have little rocket boosters? I mean they're not rocket boosters or something else, but effectively little propulsion systems built into his boots and into his palms I don't see a problem with that either. You could imagine engineering something we understand today like a jet engine You could imagine engineering a tiny version of that If you had enough power to supply to it, it could accelerate air or and push it back out And that would give you the boost that you need. So I don't see any deep problem with any of those things What about the computer system? Well, the computer system is the most impressive thing about the suit in some ways because it seems to be way ahead of where we are. His Jarvis AI is fantastic Compared to anything that we can talk to on our phones or in our computer systems today So that's a huge credit to Tony's genius that he's got that working But again, no problem from the point of view of the physics as far as I can see because Of course the human brain is approximately as powerful as that and that's allowed by physics You would just need a system like that that's in some other way Distributed in the armor so I don't see any problem with any of those features But we should think for a minute about the power systems Oh and before that I should say of course the little weapon systems like little missiles and things Nothing to say about that from the point of view of the basic physics Why not? Why not have tiny missiles that are very explosive? Can't do it yet But there's no reason to think that we're anywhere near the limit on that Okay, so then the power system. This is interesting because if we tried to build Tony's suit today We could have a go at most of the components But what would stop it from working especially stop it from flying is that we would not be able to build a small light Power generator that would get the whole thing going and that's actually part of the film is that's the missing ingredient when the When the villain of the piece tries to make his own suit He can't get that bit working and he has to steal it from Tony So that is a really interesting heart of the suit really it's a miniaturized arc reactor We're told now an arc reactor isn't a thing from the real world So we can only guess at what how it might work But we can use physics to put some limits on what any kind of power system will do and check that it all works out So fortunately in the movie Tony actually tells us How much power his prototype his first version of the arc reactor produces? What could it generate if my math is right I don't know I says Three gigajoules per second. So we're told there that it produces three Gigajoules per second now That's actually a ton of energy a gigajoule per second is also called a gigawatt Three gigawatts is what a power a nuclear power station might produce a good-sized nuclear power station would have that as its power input So Tony has somehow created a little thing that fits in the palm of your hand But at least for a while can produce the same power output as a nuclear power station But hey, he's a genius the question is is that okay with physics can such a small thing in principle produce so much power Well any system that is going to produce power will have to consume something so have to consume some fuel It's only a little gadget so we can't consume a lot of fuel Let's suppose that it consumes one gram of fuel So a little amount of fuel which we wouldn't which we easily could fit inside the thing And we wouldn't even notice whether it been consumed or not how much power or how much energy I should say can we get out of one gram of material a little bit of matter in the maximum allowed by physics The answer this is really really interesting. It uses an equation from physics that you have heard of I don't care if you never even did high school physics You have heard of the equation that I need to use now to figure out the limits on what the arc reactor could do That equation is Einstein's equation e equals mc squared So there the m is the mass of the fuel which is one gram and the e is how many Jewels of energy are going to be released, which is what we want to know So we need to work out this c squared number the speed of light squared speed of light in meters per second Which is what we should be using is Actually three with eight zeros after it 300 million meters per second fast enough to go around the earth seven times per second By the way, so I'm pretty fast and we've got to square it We've got to square the speed of light. So it's going to be huge Let's do that three threes a nine will call that 10 and those eight zeros when squared will give us 16 zeros So c squared is about one with 17 zeros after it So one with 17 zeros after it so huge number When we multiply that by our little amount of matter, which is one gram That's a thousandth of a kilogram. So we'll knock off three of our zeros But that's still going to give us 14 zeros. So that's how many joules of energy we could get out of a gram Or how much is that in gigajoules where the gigajoule would be one with nine zeros So it's still we still got five zeros left. So that would be a hundred thousand Gigajoules Tony tells us that his device can produce three gigajoules per second So that would mean it could run actually for according to physics the absolute limit that a device was remember We're not working out Tony's we're working out the limit that he mustn't go above But so our device that's perfect generator allowed by physics would actually be able to produce the amount of power that Tony wants for What 30 about 30 33 thousand seconds before it would even use one gram of fuel So the bottom line Tony's generator can produce a ton of power same as nuclear power station But such a little thing could produce that much power quite easily The limiting machine that would be allowed by physics could actually do way more than his gadget So the the final thing we should just quickly check on the power side of things is is this enormous amount of power Actually enough to do the stunts that Tony does the incredible things the suit does can this huge power level We suspect the answer is going to be yes, right because the output of the nuclear power station But let's just check so one thing to do one way to check it would be today How much energy does it cost for Tony to go up 10 kilometers straight upwards 10 kilometers from the ground? That would give a rough sense of the energy costs of zooming around and as long as it's small Compared to the amount of power coming pouring out of his arc reactor, then we're going to be okay with things all right, so How can we work that out? We need to know how heavy Tony and his suit is or how much mass it has let's say Tony is 75 kilograms Let's say the suit is heavier than him But not crazily much more heavy because you know we don't get the incense the sense that it's a massively heavy thing So let's say that Tony plus his suit is 200 kilograms and then it's going to go up by 10 kilometers, which is 10 to the power of 4 meaning 10 with four zeros after it meters So we need to do a little multiplication, which is the weight or the mass of Tony and his suit times the distance upwards times The gravitational force on each kilogram that he's having to oppose by going upwards And so that number is 9.8. Let's call it 10 So we need to do 200 times 10. That's 2,000 times 10 to the power of 4. So that's 20 million Joules 20 million joules is how much energy quite a lot of energy, but it takes to take the suit up 10 kilometers and Maybe His his thrusters are not a hundred percent efficient It's not really possible to convert energy into thrust with 100 percent efficiency Let's even say even though he's a genius Let's say that those aren't those boot things are not great. So let's say they're 10 percent efficient But remember he's his reactor is producing three gigajoules per second So it seems fine even that extreme maneuver is within the capabilities of the arc reactor and given that I think we can also allow him to use some of his boost power You know in an offensive way and run his computers and I think there's no problem with the super strength Feets because if you look in a let's say a factory which manufactures cars You'll find big robots that can basically pick up a car a car and twirl it around those robots will not use Anything like the output of a nuclear power station. So Again, he's good. He's good in terms of having plenty of power for all the feats that we see him achieving So do I have any problem with it at all? Yes, I have a problem with it But it's it's and it's such a surprising thing if you it can't already spot what it is It goes all the way back actually to the toughness of the suit the fact that it seems to protect him from any kind of Impact we need to talk about that because it is actually a problem this the thing is what I'm going to explain It doesn't make any difference how strong the suit is the suit could even be stronger than the suit We see in the movie which does take a bit of damage even a suit that didn't take a scratch During all the violent things that Tony experiences would still not protect him because of a thing called momentum conservation Which must be obeyed and the suit can't help with So it goes like this. Let's think about the scene where a tank shell comes along and hits Tony in midair Now for simplicity we can say that Tony was essentially still Compared to the tank shell which came in from the side and whacked him now the suit is super strong So it stops the tank shell from tearing a hole through his body and going out the other side In fact, the tank shell will not be able to touch Tony's body because it's inside this invincible suit But still that event would kill him as we see it portrayed on screen. Why so the problem is this That the tank show comes in very fast It would actually come in I look this up at something in excess of a thousand meters per second comes in very fast And then it hits him now momentum conservation insists that after the event the momentum must be the same as before So that means that Tony will have to be moving backwards and the shell Well, it could bounce off But that's worse for Tony because then he has to move back even faster to make up for it So the best thing for him would be if the shell carries on moving with him at the reduced speed after the impact But even then he will have had to suddenly have accelerated very dramatically in a short amount of time This is the problem. So we could work out what that acceleration would roughly be if we say that the tank shell is 5 Kilograms, which again, I looked up and that's apparently about right for that kind of tank Tony himself We already said is 200 kilograms And so what this means is that if we say that the tank shell comes in and then they move off together They will move off at roughly in the ratio of their masses So then a 40th, which is the ratio between the 5 kilograms and the 200 Roughly a 40th of the speed that the shell came in So a 40th of a thousand meters per second, which is 25 meters per second. That is quite fast. It's not shockingly fast It's about 25 6 is one big 150 so that would be 1.5 kilometers per minute Which is the sort of speed that you might do in a car down a motorway So it's nothing shocking But what's shocking is that Tony has to go from a standing start to that speed in a tiny amount of time How much time or basically the amount of time that it would have taken the Tank shell to pass through him if it was going to pass through him, but it didn't hit him So then they're going to move off together. How long would it have taken to go past him? Well less than a thousandth of a second because it's doing a thousand meters per second coming in and He's less than a meter in this direction. So let's say a thousandth of a second being generous to Tony He's got a thousandth of a second to go from nothing to 25 meters per second That is an acceleration albeit very briefly he has to have an acceleration of 25,000 meters per second per second because he did it in such a you know only a thousandth of a second Okay, so an enormous acceleration. Would the human body be able to tolerate that? Well, my body is tolerating a force that's trying to make me accelerate right now Which is the force due to gravity. It's trying to make me accelerate downwards at 10 meters per second per second But it's not succeeding. Look, I mean, it's it's trying to pull my arm off right now, but my arm is fine So we are designed or evolve to put up with that kind of force and it's absolutely fine If you go in a fast car You know round a corner or if you go to a fairground and experience forces there Then you might experience several G several times gravitational force in one direction or another going around a steep corner Or on a roller coaster or something like that and again, your body can put up with that for a while and it's fun If you think about though very dangerous levels of force then I gather from looking online that a hundred G a hundred G Which would be a force that would accelerate you a thousand meters per second per second Would be the kind of force that may be fatal for a human or you may luckily get away with it If you were in say a car accident with those kind of forces were involved So that would be a thousand meters per second second would be around the Lethal level that you might or might not care where with but we're asking Tony to do 25 times more than that 25 times over what we might say is the human limit approximately the human limit now He's a fit guy and he's a hero of the film But I don't think it's reasonable to think that his body can withstand 25 times what other people's bodies can withstand So what would actually happen the shell would come in it would push against the suit Accelerate the suit the suit inside of the front of the suit would push against Tony and accelerate him But at a rate that his body cannot withstand the forces going through his body and trying to you know accelerate His internal organs and so on are communicated through his flesh and bone And they just would not be able to put up with that So what he would end up doing is being horrible say it But he would be pasted against the inside of the suit at the front inside of the suit So that when he crashed and they came and opened up his suit He would just be Tony paste on son the inside of the suit And there's no way around this the suit It the strength of the suit does not protect him from this now a similar problem comes When he hits the ground It's less extreme, but it's still I think if you run the numbers would be likely a fatal impact when Tony hits the ground We see him in the cup of the scene sitting the ground He seems to go into the ground only about a meter and so in that very short distance He has to decelerate from doing a very rapid speed like something like 25 meters per second to zero and again His body won't be able to put up with those internal forces. It will be pasted So the problem with the suit is that it can't protect him from momentum conservation Is there anything that you could do about this if we were trying to design Tony's suit for him and fix this problem What would we do? Well, this the solution that might be allowed by physics most easily would be to have thrusters That are not only in his boots and his palms, but which are distributed over the outside surface of his suit So that when he is about to receive an extreme acceleration event the thrusters can fire and cancel it So for example when the tank show is coming in at the moment of contact Thrusters would need to fire out the back of his suit to cancel out the incoming force And it would still satisfy momentum conservation by the way because the momentum would now be in the form of let's say the air Molecules or whatever it is that he's shooting out from his thrusters They would be moving off very rapidly in that direction so that he doesn't have to and similarly when he's about to hit The ground back thrusters could fire and allow him to more gently come to a halt But we don't see that in the movie. He doesn't have that feature What else could he do? Well, then you're into some if you want it to be like it is in the movie without the extra thrusters And he is just okay through these extreme acceleration events Then what we need to do is go is appeal to physics that doesn't really exist physics like in Star Trek for example, which we're supposed to be now 500 years in the future or something and We see a starship accelerate from a standing start to extreme velocities even faster than the speed of light because they can do that And what what doesn't happen is the bridge crew all gets pasted against the back of the bridge because of the extreme Accelerations this doesn't happen and why doesn't it happen because they've got something called inertial dampers Which is not a real thing It's just the writers of that story putting in something a mystery technology that makes it okay But Star Trek can have mystery technologies because it's so far in the future that they are Breaking the laws of physics as we understand it They do things that look to us like magic, but I don't think we can reasonably allow Tony to have that kind of thing What it would need in fact this inertial dampers type thing it would need inside his suit He would have to have a technology that can push on every molecule of his body with just the right force to make it accelerate Or decelerate correctly without having to pull or tug on the molecules around it because that's the problem It's the problem is that hit the insides of his body are not designed to communicate those kinds of extreme forces So we would need to take that problem away by directly pushing on every particle of his body with something like a fake Gravitational field would do it so if we could fake gravity if we could generate a gravitational field inside his suit That's just in the right direction at the right time. Yes, we could accelerate him safely But we don't know how to do that We don't know if that's even possible We would think that it isn't possible and I don't think Tony has got that kind of tech because if he had you know He'd be he'd be in a Star Trek type universe and not in the one we see in it So that's my that's my objection which is you know You could say it's a like nitpicking objection, but I think it's really an interesting one Basic to the physics of any kind of scene where you see someone Surviving something because they seem to be inside of inside some kind of protective enclosure. So there we are I think you know, it's a high score for the credibility of the Iron Man suit If you allow that he's clever enough Tony Stark is clever enough to build such an advanced power generator The miniaturized arc reactor then the abilities of the suit all make sense. They're fine The only problem we have is just in a few scenes I think actually in three key scenes in the movie where an extreme Acceleration event or deceleration event happens and we are given no reason to think that Tony has such advanced tech That he can prevent the Consequences of that acceleration event on his own body for even though it's inside the suit So there we are. That's my only criticism of the science really or the only one that's sort of fundamental in the physics And I hope that doesn't like annoy you because I mean, it's a great I'm not criticizing the film. I think it's a great film It's correct to have these dramatic scenes like a tank shell hitting him and so on It's great fun to watch but the physics of it is not is not possible as presented Okay, so I would like to make at least one more of these where I look at a different superhero and I'm going to look at if I do it I'm going to look at the superhero that is my favorite growing up as a kid and still my favorite Which is the Incredible Hulk and you might think that I'm if I was critical of Iron Man I'm going to have to be super critical of the Incredible Hulk But not necessarily maybe maybe not but not necessarily not necessarily Because I want to focus on just what physics allows and not for example what biology allows So we'll see but I try to be kind to the Incredible Hulk because he is my favorite Okay, if you want to see that video then do go ahead and subscribe And if you found this one interesting drop it a like or drop a comment in if you disagree with me You think I've been unfair or too fair to Iron Man and you think you know the science in it is either Perfectly fine or absolutely rubbish then leave a comment. Okay. Thanks a lot