I'm a little late looking at this trailer from The Avengers 2: The Age of Ultron. You can watch the clip, but here is my version of the important part.
You would think that Tony Stark understands physics. The movie version of Stark is supposed to be like Elon Musk (who clearly understands physics) but it doesn't seem like it in this case.
What Is Wrong With Tony's Lifting Plan?
There are essentially four strategies Tony uses to lift the hammer (to attempt to lift the hammer).
- Lift the hammer with just his human body.
- Lift the hammer with an Iron Man glove.
- Lift using the Iron Man glove with the rocket thrusters turned on.
- Lift the hammer using the Iron Man glove and have War Machine help with just his glove on.
Of course he couldn't lift it as a human. I mean, he's mostly just a normal human in terms of strength. But what about using the Iron Man glove? Isn't that a good idea? Let's assume that the Iron Man suit does indeed give super human strength (which it does). Just using the glove isn't really going to help.
Before we look at lifting strategies, we have to say something about why you can't lift the hammer. I am going to use the theory that the hammer is super massive. In order to lift it, you need to exert an upward force greater than the gravitational force on the hammer. So, is Thor just THAT strong? Stronger than The Hulk? No. The hammer changes in someway to allow Thor to wield it. Clearly it's not just a plain hammer. It has to be able to adjust its weight to prevent someone for picking it up. If you say it always has a giant mass and thus a large gravitational force, how could it sit on a table? Wouldn't it just push right through the table? So I am going to say that the hammer can change its mass (or at least change its gravitational pull on the Earth).
Ok, even though the hammer is weird, Tony Stark is still dumb. Here is a force diagram showing all the forces on the hammer as Tony pulls on handle.
These are all forces ON THE HAMMER. The hammer is at rest so all of these forces must add up to a zero net force. This means that if the gloved hand where to pull up with a force of 100 Newtons, the gravitational force pulling down could be 110 Newtons and the table could push up with 10 Newtons - for a grand vertical total of zero Newtons.
That makes sense, right? But now let's look at the forces on just the glove. I will assume that the mass of the glove is small enough to ignore.
No matter how hard the Iron Man glove can pull on the hammer, something has to pull up on the glove and that something is our physics failing friend of Tony Stark. In fact, this glove doesn't give you super lifting strength, it just gives you super grip - probably Kung Fu level grip.
Now, if Tony had used the whole Iron Man suit then that would at least be a smart strategy. With the whole suit, the rest of the suit pulls up on the glove. However, there is still a problem. If Iron Man pulls up on the hammer with a force of 5,000 Newtons, then the hammer pulls down on him with a force of 500 Newtons (since forces come in pairs). This means that in order for the Iron Man suit to stay at rest, the floor has to push up on the suit with a force equal to 5,000 Newtons plus the weight of Iron Man. I suspect the floor could handle something like 5,000 Newtons - but could it handle 50,000 Newtons? At some point, the floor is going to break. No one is lifting that hammer unless the hammer wants to be lifted.
But wait! Tony also tries something else.
Ok, the rocket idea makes sense. The rockets on the glove would be able to exert a force that wasn't dependent on Tony's human strength. Also, these rockets don't require the floor to be strong since they aren't directly pushing on the floor. Of course, these are just tiny rockets so that I doubt they would help that much if Mjölnir doesn't want to be lifted.
What's Really Going On?
Lifting the hammer with the Iron Man glove was not such a smart thing to do. Using the rockets seems only marginally better. So, then why did Tony Stark do it? Here are some options.
- Tony Stark doesn't understand physics. This is the simplest explanation for his actions. However, if he doesn't understand physics then how did he build the Iron Man suit? I think the answer is that the computer Jarvis built the suit and S.H.I.E.L.D. along with Tony's father (Howard Stark) built Jarvis. Oh, of course this is different than the comic books.
- Tony Stark is drunk and doesn't know what he is doing. Or maybe he is on some type of recreational drug. It is Tony Stark - he likes to drink.
- Tony Stark knows that only a worthy being can lift Mjölnir and he also knows he is not worthy. However, in an attempt to appear that he is trying (even though he knows he will fail) he uses the Iron Man glove. He doesn't use the whole Iron Man suit because he wants Black Widow to be able to see his face in an effort to impress her.
- Tony Stark is super smart. In fact, he knows that Ultron is about to bust into the room and that Ultron is probably watching. By trying to lift the hammer with a glove, he is giving Ultron the impression that he is stupid and thus not a likely threat. We often call this "subterfuge".
But what about the physics of Thor's hammer (Mjölnir)? Yes, there are some interesting physics questions to consider. In some origins of Mjölnir, it is stated the hammer is forged from the core of a star. Could this happen? What would it's mass be? Great questions indeed.
The answer to these questions can be found in my new (and soon to be released book)---Geek Physics. I'll give a more detailed review of the book soon, but for now I will just say that this is sort of like a paper version of Dot Physics. Some of the topics in the book are reworked from previous blog posts, but the physics Thor's hammer is something just for the book.
