Captain America's Shield: The Physics thread

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Ted C
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Captain America's Shield: The Physics thread

Post by Ted C »

So, here's a hypothesis for the various behaviors we've seen of the shield.

The shield absorbs kinetic energy, but momentum still has to be conserved. This means Cap can still feel a blow to the shield and still be knocked around.

Not all parts of the shield absorb energy equally. He can strike with the edge and do harm, while taking a blow in the shield's center that would break bones.

There's a limit to how much energy the shield will absorb. More than that limit is reflected back the direction it came from.

Other idea?
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Re: Captain America's Shield: The Physics thread

Post by Ahriman238 »

Are we accepting movie evidence? Comics? Animated?
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Re: Captain America's Shield: The Physics thread

Post by Ted C »

This is mostly a Cinematic Universe thread.
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Re: Captain America's Shield: The Physics thread

Post by Ahriman238 »

Ah. Okay. In that case, the most impressive things we see the shield do are let Cap survive an overhead strike from Thor, and resist the HYDRA disintegration beams countless times. Well, the Glowstick of Destiny too, I suppose.
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Re: Captain America's Shield: The Physics thread

Post by Gaidin »

It all depends on the amount of force obviously. I think Conservation of Momentum is right in a comic book sense.

Thor's Hammer threw Thor back with how much force that thing threw onto the shield, but with how little force Bucky could comparatively throw onto the shield with 'just' a cybernetic punch it just sorta stops him and he starts pushing down from there, if that makes sense. At least as far as the shield blocking blows anyway.
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Re: Captain America's Shield: The Physics thread

Post by Napoleon the Clown »

The edge not absorbing blows isn't enough to explain how we've seen Cap use the shield. He's smashed faces in with the front of the shield, too.

Maybe some property of the shield allows force (and rapid acceleration) to be applied from one side but not the other, or some shit. So Bucky's punch initially stops, but he keeps pushing and the acceleration is slow enough to not trigger some sort of reaction in the shield that would stop it. And when Cap smacks a bitch the shield allows him to apply force since the acceleration originated from his side of the shield. Or something.
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Re: Captain America's Shield: The Physics thread

Post by Gaidin »

You're still just talking about amount of force in essence and it stems from Thor >>> Bucky > Cap smacking a bitch.
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Re: Captain America's Shield: The Physics thread

Post by Havok »

The cinematic universe is just as silly as the comic version. There is no way to explain it other than with made up "science".
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Re: Captain America's Shield: The Physics thread

Post by InsaneTD »

What if the amount of energy absorbed is proportional to the strength of the attack? Bullets aren't just stopped dead in the movie, the ricochet off, so the shield is doing Bugger all to their energy, might not even do anything to it, the shield thickness and captain's strength being enough. Attacks that can't be absorbed are reflected instead.
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Re: Captain America's Shield: The Physics thread

Post by Simon_Jester »

Bullets ricocheting is actually a very intuitive behavior for the shield- it's a thick slab of metal held by a very strong man. Bullets would tend to ricochet like that off a steel plate, too.

Personally, I think the problem is that in the movies they have the shield act more or less like we'd expect a metal slab to work against 'human-scale' threats, things like punches, bullets, and being thrown. But against things like artillery or ray guns or the hammer of Thor, it acts differently than you'd expect from just handing a guy an infinitely tough slab of metal and saying "good luck!"

So any anomalous behavior must be applying to very energetic events.
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Re: Captain America's Shield: The Physics thread

Post by Grumman »

While it isn't a perfect match, the way I'd treat it is to say it negates force applied to the front of the shield, and that's it. It can't negate force applied to the edge of the shield or it couldn't ricochet, and it can't negate force applied to the back of the shield or Captain America couldn't move it. And it obviously doesn't negate force applied by the shield or he couldn't hurt anyone with it.
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Re: Captain America's Shield: The Physics thread

Post by Kojiro »

InsaneTD wrote:Bullets aren't just stopped dead in the movie, the ricochet off, so the shield is doing Bugger all to their energy, might not even do anything to it, the shield thickness and captain's strength being enough.
Actually no. They are stopped dead. Rewatch that scene- the bullets drop to the ground right at Cap's feet.
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Re: Captain America's Shield: The Physics thread

Post by InsaneTD »

Well that blows my theory out of the water. I hadn't noticed that.
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Re: Captain America's Shield: The Physics thread

Post by Havok »

That's why I said it is silly. Like the comics, the shield is basically magic and does what is needed for that particular scene/panel.

Hot chick pissed off at Cap for flirting? Bullets stop dead.
Red Skull shooting at Cap? Bullets ricochet and kill the henchmen about to get the drop on him from behind.

The only thing the shield has ever done consistently is block fire completely while Cap kneels behind it and come back to Cap's hand, unless impeded.
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Re: Captain America's Shield: The Physics thread

Post by Ford Prefect »

The shield is like Steve Rogers' patriotism made manifest as a physical object. It certainly has properties, but none of them really correspond to the material universe as we understand it.
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Re: Captain America's Shield: The Physics thread

Post by Napoleon the Clown »

So the shield is to Captain America as the feather is to Dumbo?
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Re: Captain America's Shield: The Physics thread

Post by Ford Prefect »

It is both that and an actual physical object supposedly made out of an actual physical material, though by 'actual physical' I mean 'not real'.

One of the endearing things about fiction is the way in which objects can stand for an represent ideas and those ideas can in turn have effects upon the events within the fiction. The shield represents Rogers' unwavering faith in his particular set of ideals, formulated by reference to his beliefs of what 'America' is. As those beliefs are unshakable, the defence afforded by the shield is impenetrable. This is just a variant of Hav's (quite accurate) 'it just does whatever' thing, but you know.
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Re: Captain America's Shield: The Physics thread

Post by SCRawl »

Oh, I'll give it a shot.

Objects with relatively low energy striking the shield normal to its surface will have all of their energy absorbed by the shield, and then quickly dissipated as heat. Objects striking the shield at an oblique angle to its surface will still have the normal portion of their energy absorbed, but whatever their lateral energy is remains. In other words, if you're standing right in front of the shield and you shoot it right in its centre, the bullet will just deform and fall to the ground. If you're standing at the same spot and aim closer to its edge, it will ricochet with a portion of that energy.

Large impacts to the shield (such as the overhead blow from Thor's hammer) are absorbed and immediately redirected in the direction from which they came. (This is awfully hand-wavy, I know, but I really can't think of something that works well.)

The edges of the shield were heat treated differently from the rest of it, giving them greater hardness. (It's all still one piece of vibranium, but the crystalline structure is different.) So the edges are less able to absorb energy, but are able to deliver blows.

As for delivering a blow with the front of the shield...I've got nothing.
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Re: Captain America's Shield: The Physics thread

Post by Napoleon the Clown »

I dunno, I think I'll just think of it as being a regular old shield and Steve gained more than just physical prowess, he also gained subconscious psychokinetic abilities. Howard Stark (wasn't that who showed him the shield, my memory is fuzzy) was just taking the piss about the shield's abilities. That's how the paint can get fucked up, too. Steve believes that it will be damaged, so it does get damaged. Bucky can catch the shield because Steve subconsciously believes his cyborg arm will allow that. Same with the punch scene. It's also why he can bounce the shield off people with such precision.

As to why Thor's strike with Mjolnir caused the massive shockwave, Steve believed that all the force applied would go somewhere and subconsciously decided that's where it would go. So it went there.


I don't actually believe this is what the writers had in mind, but it's honestly just as good an excuse as anything else.
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Re: Captain America's Shield: The Physics thread

Post by White Haven »

...Captain America is not an Ork.
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Re: Captain America's Shield: The Physics thread

Post by Napoleon the Clown »

Of course he isn't! He doesn't reproduce with spores. That would just be silly. He also seems to be a bit brighter than a typical ork.
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Re: Captain America's Shield: The Physics thread

Post by InsaneTD »

What if they misinterpreted the results they got when first testing the material, and instead of absorbing energy, it reflects/redirects it? A bullet hitting dead centre would stop dead because all it's energy is reflected back at it, where one striking at a off angle would ricochet off with little loss in energy. It's been a while since I've seen the original, does the beam weapons stop or radiate/reflect off?
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Re: Captain America's Shield: The Physics thread

Post by Grumman »

I agree with White Haven. It would be like saying Batman isn't a good detective, he's just a clairvoyant. It undermines the character.
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Re: Captain America's Shield: The Physics thread

Post by Alkaloid »

It's been a while since I've seen the original, does the beam weapons stop or radiate/reflect off?
Starks suit repulsors reflected off it in the Avengers. They seem to deliver a lot of kinetic energy with relatively little heat as well, so bullets presumably do the same.
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Re: Captain America's Shield: The Physics thread

Post by Havok »

OK, how about this. The shield is neutral. What I mean is that it absorbs everything and when Cap deflects a bullet it is Caps arm delivering the energy to do it. So when Cap just stands there like in the scene where the chick shoots at him, the bullet just falls. But when a bullet gets deflected Cap uses his peak strength to kinda flick it the direction he wants. Think of it like him punching the bullet back or in the direction he wants.

Also Cap's shield is usually shown in three separate rings and then the center piece when unpainted. I didn't see anyone say this specifically, but could each ring have a different property?
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