Physicist Provides Scientific Explanation for Why No One Can Lift Thor's Hammer
In the recently released Avengers: Age of Ultron footage that premiered during Agents of S.H.I.E.L.D., the Avengers step up one by one to attempt to life Thor's hammer. None succeed, of course (although Captain America came too close for Thor's comfort), causing Thor to jokingly proclaim them "unworthy." And, indeed, the mythology in the comics states that the Mjolnir can only be lifted by someone who is "worthy." But how does the hammer determine who is worthy? And once it does decide, how does it prevent itself from being lifted? In a recent Wired article, physicist and astronomer James Kakalios provided answers to these very scientific questions.
"Norse mythology and Marvel Comics tell us that Mjolnir is composed of 'uru metal,' forged ages ago by the blacksmith Etri in the heart of a dying star," explains Kakalios. "Presumably uru metal is magical in nature, and thus conveys the enchantment placed on it by Thor's father, Odin. But in this matter we are not concerned with the fantasy of myths or comic books, but the real world of Hollywood movies."
First, he debunked the theory put forth by Neil deGrasse Tyson that the hammer is physically too heavy to lift without superpowers. If, as Tyson hypothesized, it was made of neutron star matter, the densest material in the universe, then it would weigh approximately twelve thousand trillion pounds. In that case, it seems unlikely that either Tony Stark's coffee table or a random book would be able to support its weight, as seen in the Avengers: Age of Ultron footage:
(Plus, it would be a bummer if "worthiness" were determined by physical prowess.)
So Kakalios proposes his own explanation. The mythology behind Thor is more sci-fi than fantasy in the movies, and his race of "gods" are supposedly alien beings who are scientifically advanced to the point that their technology appears to be magic. So the uru metal is not magic, but has distinctive physical properties that afford it its "powers." First, it must have nanotech embedded within it which allows Odin to reprogram the hammer with his voice when he says the famous words in the first Thor film, "Whoever holds this hammer, if he be worthy, shall possess the power of Thor."
But then there's still the question of how the hammer executes this instruction. Tony Stark theorizes in the footage that there's a biosensor which recognizes Thor's fingerprints, but this wouldn't be consistent with Captain America moving it slightly, presumably because he is generally a more stand-up guy. So the nanotechnology must have biosensors that have the ability to create a full psychological profile from some kind of biological marker.
But then, once the Mjolnir decides that someone is unworthy, how does it prevent itself from being lifted? The answer, according to Kakalios, lies in Newton's First Law of Motion, which states that an object at rest will remain at rest unless there is a net force exerted upon it. So the Mjolnir will only be lifted if the force exerted upon it is greater than the gravitational force pulling it towards the ground (or the coffee table). Presumably, if it doesn't fall through the coffee table, then Iron Man's glove should exert a force on it that is greater than its gravitational force, which means that it must have the ability to emit particles called gravitons, which increase gravitational force, when it detects "unworthiness."
"When Tony Stark tries to lift Mjolnir using his Iron Man glove, he exerts a large upward force, greater than its weight, and yet the hammer remains at rest. So where does the additional downward force come from? One can only conclude that a unique property of uru metal is that, under the proper stimulus, it can emit large quantities of gravitons. On Earth, these fundamental particles have not been experimentally confirmed to exist, but as stipulated, the Asgardians are ahead of us scientifically. Gravitons are conjectured to transmit the gravitational force, and if an object emits additional gravitons, it is equivalent to increasing its mass. Thus, when an 'unworthy' person applies an upward force, the uru metal increases the hammer's weight to exactly cancel this lift, and the hammer remains unmoved."
Or, you know, it's magic. That works, too.