For real? We ask a physicist to ruin our favorite action sequences

Gravity
Blockbuster Hollywood action flicks. They rock. Where else can you pony up $10 and get edge-of-your-seat thrills that last 90 minutes?

Almost as much fun as watching them is, well, nit-picking them with your friends afterward. You know what I mean: “D u d e … there is totally no way that Batman could have ridden the Batpod that way in real life, I mean C’MON!!” But how can you tell what was pure, unadulterated movie magic and what was — perfect conditions assumed — actually possible in the real world?

Here’s how: Ask a scientist! So we did. Not just any scientist, mind you. Nope, we went straight to a physicist who doesn’t just the talk the talk, he totally walks the walk. Dr. Austin Richards, A.K.A. Dr. MegaVolt, who — just like Bruce Wayne — dons a special suit in which he regularly risks his life, courtesy of a pet Tesla coil that just happens to generate a million volts of electricity.

You need to have a pretty firm grasp of both physics and reality when playing with lightning is your hobby. So we’ve got a reasonable degree of confidence that when Dr. Richards says, “That ain’t real,” he’s on the level.

Here then, are five of the, ahem, bats–t-craziest movie scenes from the past two years, with a brief reality check, courtesy of Dr. MegaVolt.

Scene 1

Air Force One Rescue – Iron Man 3

Reality Rating: 1/5

Why it works

Strangely, getting 13 people to link up during a high-altitude skydive isn’t the problem with this scene. In fact, the mid-air sequences were shot with the help of a professional skydiving team who performed the link-up as it’s seen in the film. Where we have to make some much bigger leaps of faith is at the end of the sequence.

Why it doesn’t work

First off, some basics: People who fall out of jet airplanes at cruising altitude do so going about 600MPH at 35-39,000 feet. In other words, they simply don’t do it without a helluva lot of specialized equipment. Hypoxia from the altitude alone could be lethal.

Now, assuming Tony Stark’s Iron Man suit was capable of generating the thrust needed to slow about 1600 pounds of mass from terminal velocity to a safe-ish water landing speed (a force equivalent to the thrust generated by a business-class jet engine), and, assuming Stark’s “electrification” of the first passengers in the two-sided chain could generate enough muscle tension to keep their hands closed on various limbs (you’re beginning to see the problem here right?), we must still face this inconvenient truth:

iron-man-3-special-fx-030

“The two people holding onto Iron Man’s hands have it particularly rough,” Dr Richards says. “They have to hold back their mass, plus the mass of the people below them in the chain, times about 2 gee of acceleration at the end when they are about to be released into the water.”

The calculation looks like this: An average person has a mass of about 60 kg. The flight attendant, Heather, has to hold 6 people including herself. 360 kg times 2 gee is 7.2 kN, which is 1,600 pounds of force. That would probably rip her arm off or at least severely damage it.

So how many people would be waving happily from the water? None. Iron Man himself would have to hold back 12 people total, or 3200 pounds of force. We haven’t included Tony Stark’s weight in the calculation because (spoiler alert!) he wasn’t in the suit.

Scene 2

Cherno Alpha, Crimson Typhoon vs Otachi, Leatherback – Pacific Rim

Reality Rating: 0/5

Why it works

We looked at the Jaegers long and hard (and from many different angles), trying to find something that we could hang our physics hat on and, well, there just isn’t a hat stand in the world big enough for this job.

If we were to be very generous, we might concede that if (and we’re talking an “if” the size of an acid-barfing Kaiju) it were possible to build and power a robot/mecha on the size and scale of the Jaegers, without them ripping themselves apart, they might indeed be able to pull off some of their more basic moves (walking mostly). Sorry, that’s all we got.

Why it doesn’t work

The biggest problem with Jaegers is that in order for them to do what they do, we would need everything (technologically speaking) to be different than what we have at our disposal today. But the movie doesn’t even give us leeway on that point, claiming that the very first Jaeger to enter service has its inaugural Kaiju battle on April 23 of, wait for it, 2015! We’re not even sure the Apple Watch will have launched by then, nevermind a 1,980 ton, battle-ready mecha.

Dr. Richards concurs with many of the observations made in this light-hearted critique of Jaeger engineering, and feels these facts pretty much sum up the degree to which physics has been ignored: “The Bugatti Veyron, the world’s fastest car, produces 922 lb-ft of torque. He also says the world’s largest hydraulic motor produces 1,290,734 lb-ft.” For those who aren’t so math-inclined, this translates into, “88,461 Bugattis or a little over 63 of the hydraulic motors just to hold the robot arm straight out at the shoulder.” Want more? Here’s an even deeper analysis.

Scene 3

Debris hits Shuttle Explorer – Gravity

Reality Rating: 4/5

Why it works

You simply have to hand it to Gravity’s director, Alfonso Cuarón. His obsession over the details in this film resulted in the most realistic depiction of space we have to-date (and that’s the assessment of a former astronaut, not a physicist).

In this clip, not only are the physics of the scenario well within the bounds of reality, but so is the absence of sound as thousands of pounds of space shuttle get ripped to shreds by orbiting debris. And though there have been excellent debates over just how real some of the movie’s elements and working precedents are, Dr. Richards’ take on this particular scene is: Very real indeed.

Why it doesn’t work

For the sake of this clip, let’s assume that some of the more problematic elements of the movie leading up to this scene were all possible, and happened as described. The big problem isn’t so much the physics as it is how those physics are portrayed. Dr Richards explains why:

“In the film, the Russian spy satellite debris comes around and passes them every 90 minutes, so it is at orbital speed relative to the shuttle and the astronauts (in other words, it is going ~25,000 miles in 90 minutes, which is 17,000 MPH). The kinetic energy is so high that things would shred super fast and pieces would be blown everywhere,” he says.

The debris field itself would almost certainly be invisible, thanks to its velocity. From Dr. Stone (Sandra Bullock) and Kowalski’s (George Clooney) point of view, the space shuttle Explorer would suddenly start developing holes and then appear to rip itself apart – an almost eerier prospect than the physical debris field shown in the scene.

Scene 4

Flip Car – Fast And Furious 6

Reality Rating: 3/5

Why it works

The Fast and Furious franchise is much-loved for its crazy-fast cars and crazy-fast and/or suicidal driving done by its lovable band of outlaws. Many of its action sequences make extensive use of special effects, CG and otherwise, because, by and large, vehicles just don’t do what they’re seen doing in these movies.

But there are exceptions, and the sixth installment’s “flip car” is one of them. Kind of. Turns out, if the flip car was equipped a special rail to guide the path of the oncoming vehicles, they would indeed flip exactly as they do in the movie, and that’s exactly how these stunts were created – no digital effects required.

Why it doesn’t work

“Without the help of that rail — which creates a 45-degree angle to the road surface — the oncoming cars would likely crush the flip car, especially if they collided dead center as opposed to off-center. The angled plates just aren’t long enough or angled enough to achieve the flipping power you see in the film.”

Scene 5

Bridge/Tank Scene – Fast And Furious 6

Reality Rating: 2/5

Why it works

Yes, we know, two clips from the same movie. But you’ve got to admit, the Fast and Furious movies do make for a plethora of debatable action sequences.

In this instance, things seems to obey the laws of physics for the first 20 seconds or so, inasmuch as you’ve got fast cars driving, er, fast, and a neat high-tension cable that lodges itself into the rocky sides of a freeway and magically auto-winds itself taut… but then physics pretty much takes a vacation and never comes back.

Why it doesn’t work

It’s all about the cables, folks. First, let’s deal with the tank reveal. We’ll assume that it’s meant to be a modified M1 Abrams tank, or at least, one very much like it. For weight purposes, we’ll guess it’s about 55 tons (in fact, a modified Chieftain Tank was used during filming). That’s roughly 110,000 pounds.

So that cable would have to be strong enough not to snap (or dislodge itself from the rock — a far more likely event) after being hit by the semi-truck (which would actually need to be one of these) at 41,000 pounds (plus the weight of the tank itself) at a conservative highway speed of 45 MPH, giving us 13,767 kilojoules of kinetic energy.

Now, since the whole contraption isn’t brought to a halt immediately (it looks like the cable has some give to it), we’ll say it came to full stop in 10 meters. To do that, the cable would need to withstand a force of 1,376.7 kN without breaking. A two-inch thick steel cable might be able to pull off this feat, but it would be a stretch.

Fast-And-Furious-6-Bridge-Tank-Scene

The next piece of cable magic comes at the end of the sequence when that same tank is reduced from its full-tilt run to a dead stop the moment the dangling Mustang catches on the bridge’s legs. The same math applies, only this time, with the shorter stopping distance (let’s say 2M), the cable (which looks far less robust than the one used to stop the convoy) has a far bigger load to contend with.

“Let’s be generous and reduce the tank’s weight to 100,000 lbs. At 45 MPH (which is 20 KMH less than the producers said their modified tank was capable of), our steel cable must now try to weather an astonishing 4,535.9 kN of force, which is about 1 million pounds!” Dr Richards points out. You’d need a cable thicker than the diameter of those used on the Golden Gate Bridge’s vertical deck ropes to handle that strain without breaking.

Speaking of breaking, given that the cable connecting the tank and the Mustang-cum-anchor looks to be wrapped around the tank’s main gun and not attached to something a bit more solid like the front of its under-carriage, you’re stuck with the conclusion that the barrel of the gun could withstand this same force without snapping. But some Chieftain tank barrels have been known to bend just through normal use.

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