Our resident Hollywood physicist takes on The Dark Knight and comes up victorious

Watch the Physics Fly Warner Brothers

With The Dark Knight, the action-infused sequel to Batman Begins, dominating the box office in recent weeks, it’s clear that the revitalization of the new Batman franchise is no fantasy. In my opinion, The Dark Knight doesn’t quite come up to the level of its predecessor—its relentless action sequences left me a bit numb after a while, and the constant quick cutting in these scenes gives the audience too much to absorb all at once. Nevertheless, it’s got some very good performances (notably, the late Heath Ledger's much acclaimed portrayal of the psychopathic Joker), an intricate plot and dramatic psychological conflict.

Meanwhile, the action sequences, and the use of technological gadgetry are on par with a James Bond movie, and The Dark Knight provides an ample springboard to apply some Hollywood physics. There are so many chases, collisions, jumps, flights and explosions it’s easy to highlight a few of these for some exciting physical analysis. We’ll also take a look at some of the fancy gadgets and discuss the physics (or lack thereof) behind them: There’s a lot there. So let’s highlight some relevant scenes.

Click here to delve into “The Physics of Batman.”

Adam Weiner is the author of Don't Try This at Home! The Physics of Hollywood Movies.


Did you even watch the movie? In the scene where batman bent the barrel of a gun, he had a type of exoskeleton on his arm and hand to help him. Maybe he used this when he was gliding as well? I thought you might have picked on the Batpod a bit more, taking a corner on that would've been impossible with those tyres. But you seem to have forgotton the fact that this is a comic book film, it's a brilliant piece of theatrical art! It dosen't have to be correct, it's fantasy. Just try to watch it without picking holes in it, you might appriciate it a bit more.

I agree with strange 009. This article is pretty terrible and shows incredibly poor knowledge of the movies being written about. The Garbage Truck/ Semi mistake could have easily been avoided by a 10 dollar trip to see the movie again after writing the article, or even just by letting someone who was actually paying attention to the movie read this article before it was published. This is just poor work. Did it not occur to the author that if Batman had run into and destroyed the Joker's Semi, that it doesn't make very much sense that Batman is flipping it over 5 minutes later?

Why would you both register on a science website just to both look like idiots? I really don't get it. All this guy is trying to do is apply actual physics to a movie to see how the two compare. It has nothing to do with the movie plot or the series or anything of that nature. Oh and learn how to spell. Tyres...really?


Tyres is an accepted British English spelling of tires.

Also, if you read the article, which you clearly haven't, you would see that a lot of the assumptions the author makes are foolish. For instance, he assumes the tumbler runs into the semi truck and pushes it up into the road above. His major qualm with the physics is that the Joker would have been killed as he smacked into the front of the semi trailer. However, the tumbler runs into the garbage truck which was ramming the swat truck. The garbage truck doesn't contain the Joker. His argument is based on an event that doesn't happen.

He also assumes that the batpod uses it's momentum to flip the semi truck, when it is clear that isn't what batman did. (That would be outlandish, which is funny because that isn't what the author argues about.) He clearly wraps the cord around several sturdy light poles and lets them stop the truck as the fall and get caught against buildings. The author also assumes that the cord used is only a cm squared in cross section (which is tiny) and that the truck is stopped instantly, when it is actually stopped within the time frame of a couple of seconds. The calculations he does are just irrelevant given the assumptions he makes.

Why would you register on a science website just to look like an ignorant dolt? You and the author both suffer from the same problem. A tiny bit of research would have kept you from looking stupid, and you didn't take the time to do it.

Ok let's take a minute and clarify a few things here. First of all, those of you who point out that it is in fact the garbage truck and not the tractor trailer involved in the head on collision, you are right to make the correction, and while it is difficult to get all the details watching the movie live (twice) while taking notes, I accept that accuracy in these plot matters is important. However, before I explain why the assumptions that you criticize are in fact reasonable, I must say that I believe you are missing the point (and the spirit) of this kind of article.

Of course we all realize a movie like this is a fantasy, and I am not out to "trash" the movie, in fact I indicate in the introduction that I liked it overall although not as much as Batman Begins. Nevertheless the point here is to use the movie scenes to bring up some interesting physics principles. For those of us (who like physics and science) it's enjoyable to de-construct the scenes, and analyze them in this way. It does not ruin the movie for us, it just adds an educational element. Satirical comments are usually meant to be lighthearted, not as a demonstration of superiority.
This may not appeal to you and that's fine.

Now let's clarify a few specific points. Yes if it is the garbage truck that is in the head on collision, then my comments about the Joker flying into the wall aren't relevant to the scene and I would certainly prefer I hadn't missed that. However, the general point is to highlight a principle. It should apply equally to what would happen to the Joker in the flipping truck. In general the effects of severe accelerations are overlooked on characters in action movies. There are several other examples of this in the movie, for example when Batman catches Rachel at the last minute by opening his bat wings and landing on the car.

As far as the cable goes, you guys are wrong when you say that it acts on the truck for over a second. The major force of impact happens very quickly and the majority of the flip in the air occurs after that force ceases to act. It is given its initial rotation during a very short collision time, and maintains that rotation (Newtons first law) after the collision ceases. Collisions with rigid objects occur on a time scale of about one one hundredth of a second. The cables are not completely rigid but a time scale of a tenth of a second for the time during which the major force is applied is quite appropriate when stretched taught as they are. As is a cross sectional area of a square centimeter for the cable. That's about the thickness of your little finger. Rent the movie when it comes out, as will I, and you can see that the thickness of the cables are in that range.

I completely agree that the purpose of this article is to find a healthy way to apply our interest in physics to such an awesome movie, but when i see calculational errors it certainly makes me cringe...

When calculating the force on Batman's arms while opening his wings, the gravitational force and the centripetal force are acting in perpendicular directions (down and horizontally) and cannot just be added together. (It happens to not make much difference in this cases since one is so much larger than the other, but still.)

And I'll agree that for Batman to have that much cable handy, saying the cross sectional area is 1 cm is reasonable. However, 63 billion N/m^2 DOES NOT convert to 63,000 N/cm^2!!! It converts to 6.3 million, which is strong enough to support the assumptions made. It seems a far more reasonable argument to assume that the lightposts would have broken off (assuming that Gotham uses a common, low strength material for its thousands of lightposts).

Yikes! What a day. Yes your right about the conversion: 63 x 10 ^ 9/100 cm ^2 does equal 6.3 ^ 6. So ok yes if the cable is made of carbon nannotubes then it could be strong enough to withstand the impact and the weak link as you suggest could well be the lamp posts.

As far as the centripetal force calculation it is correct. There is no special force called the centripetal force. The "centripetal" force is simply the vector sum of the forces acting radially on an object moving in a circle. So in this case the centripetal force is equal to the component of the air resistance force acting towards the center of his circular path minus the component of the gravity force acting away from the center of the circle. I took the easiest point of the motion to analyze which is at the bottom of the arc where the air friction component is straight up and the gravitational force acts straight down. If there is any horizontal component of force it is irrelevant to this calculation although it would add mean there is still a bit more force acting on Batman's arms. In the calculation therefore we are determining the force of air friction on Batman's arms which he in turn exerts back on the air.

In reply to strange 009, you have obviously never ridden a motorcycle on the street. When you make a turn, you don't simply turn the handlebars like you do on a bicycle, what you actually do is push the bar in the opposite direction that you normally would. Even though the tire barely turns, the bike leans over and you turn. This is called counter-steering, and is how all turning is done pretty much over 10km/h. While that bat bike would certainly be hard to steer at low speeds, and that way he whips around before almost running the Joker down might be implausible, the steering he does while moving is perfectly normal.

As for the semi flipping over, that is pretty unrealistic. For that to happen, there would have to be a force applied in the Y direction. With the cable pulling the way it was, it would only apply force in the negative x direction. Just adding the vectors, it is impossible. Also, the kind of torque that would be applied should the vectors have existed would be huge, and would likely just rip everything apart before turning that thing on end like that. The semi flipping over is completely impossible in that scenario, so lay off the author.

First off, sorry to Adam Weiner, perhaps I was to harsh. There are a lot of impossible things going on in the film, but that should be expected. I love science and I love films, so I can understand what you mean.

Now, Jacubious, I know how to take corners on a motorbike at speed, I know that you have to lean in to the corner so that the bike tips quite nicely thanks to rounded tyres. (Yes, nosnhoj1078, TYRES. Get an english dictionary.) But the Batpods tyres aren't rounded enough, in fact their almost square when viewed from the front. Batman would have to be much heavier and I'm sure the overall centre of gravity would have to be placed much higher for the Batpod lean over. It looked great though, and thats the main point, isn't it?

I recently read an article about the Batcycle that said it could only be ridden by one stuntman and then only in a straight line. All the Batcycle scenes were done "green screen"

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