The Physics of Thor’s Hammer

By Rhys L Griffiths

The Mighty Thor is the Asgardian God of thunder and quite possibly the most powerful of all the Avengers.  He is super strong, can create lightning and he also wields Mjölnir, a large square-headed lump hammer that only the worthy shall lift. Thor is able to lift the hammer with ease whereas others, including Captain America, Iron Man and even The Incredible Hulk, have failed to do so.  So how is this possible?

Image from Thor: The Dark World CC Marvel

The Marvel character Thor was based on the Norse mythological deity of the same name, who wielded Mjölnir, a hammer so powerful that it could level mountains. When Marvel adapted Thor in the 1960s, they did make changes to both the Thunder God and his hammer making them both even mightier.  It is accounted that the Norse Mjölnir was created by dwarven brothers Eitri and Brokkr, but the movie’s origin claims that Mjölnir was forged in the heart of a dying star. Renowned Astrophysicist and fun squasher Neil deGrasse Tyson once tweeted ‘If Thor’s hammer is made of neutron-star matter, implied by legend, then it would weigh as much as a herd of 300-billion elephants’. Neutron stars are very small but incredibly dense, roughly two or three times denser than our sun.  If they were any bigger they would collapse in on themselves and form a black hole. A teaspoon of Neutron star would have a mass of roughly 10 billion tonnes. That’s one heavy teaspoon.  However Neil deGrasse Tyson is wrong, Mjölnir was forged IN the heart of a dying star, not OF the heart of a dying star, and according to Marvel, weighs approximately 42 pounds.  So what’s the true mass of Thor’s hammer?

Sir Issac Newton’s first law of motion states that an object at rest will remain at rest, if no net force acts upon it.  If Mjölnir is placed on a table, the force of gravity is pulling it down while the table is acting as a counter force (or normal force as it’s acting normal to any other surface).  If the mass of the hammer was that of 300 billion elephants then not only would it break the table but it would leave a pretty big hole in the floor. But Mjölnir is able to sit comfortably on the table, that is until someone it deems unworthy attempts to lift it. If I was to attempt to pick it up I could apply a force greater than the hammer’s mass but it still wouldn’t move. Mjölnir would have to emit an additional downwards force in order to remain still. In the Marvel comic book ‘Indestructible Hulk #8’, Bruce Banner says that Mjölnir can change its mass by emitting graviton particles.

A page from Marvels Indestructible Hulk #8

A graviton particle is a hypothetical particle that transfers gravitational forces from its field. By changing the gravity around itself it can be light enough for Thor to wield but too heavy for his enemies to lift. A worrying side note to include is that The Incredible Hulk gets stronger the angrier he gets, making him infinitely strong.  If he tries to lift Mjölnir then it could emit enough gravitons to sink through the Earth, creating a black hole and destroying everything.  So best to keep Hulk away from the hammer.

CC Marvel

One of the most interesting aspects of the Marvel character Thor is that he uses his hammer to fly.  The way he goes about this is by spinning it around incredibly fast and throwing it. He lets go of the handle for a split second and then grabs hold of it again, sending the hammer hurtling in the given direction while taking Thor with it.  This has angered many people as they believe it to be a violation of the principle of conservation of momentum and breaks the laws of physics.  However, this mode of transport is possible. If we look at the science we’ve already discussed and that Mjölnir has the ability to change its mass then when Thor swings it around at great speed, the mass increases thus drastically increasing the momentum.  When Thor throws it, his momentum is tiny in comparison, allowing him to hold on.

James Kakalios, author of ‘The Physics of Superheroes’ (and inspiration for the panel above) has another theory as to how Thor is able to build up so much momentum. ‘When Thor twirls his hammer, the mighty Mjölnir, he plants his feet firmly on the ground’.  Kakalios goes on to compare Thor to the X-men Villian the Blob who is impossible to move.  He plants his feet ‘so strongly on the ground that he effectively couples his center of mass to the Earth’s, such dislodging the Blob requires moving the entire Earth unless the connection is broken.’  Using this method Thor wouldn’t even need to release and re-grab Mjölnir in order to take flight, he would just need to jump a little, breaking the connection with the Earth.

So would I be able to take flight by spinning a normal hammer around quickly? No chance. I’ll leave the hammer throwing to Thor.

For more Superhero science check out:

Can I run as fast as The Flash?
Batman V Superman: Who would win?
Can science make a Spider-man?
Could Ego the Living Planet really exist?

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