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Thor’s Hammer Is Not That Heavy (But It Is Scientifically Interesting)

In early February, astrophysicist Neil deGrasse Tyson said on Twitter that the superhero Thor’s Hammer (aka Mjolnir) “weighs as much as a herd of 300 billion elephants.” News outlets pounced on this, and the news was quickly circulating online. Sadly, Tyson was wrong.

Tyson’s reasoning was based on the idea that Mjolnir was “made of neutron-star matter.” Not so fast.

(Art by Mike Deodato Jr.)

“The critical mistake Tyson makes is thinking that Mjolnir was forged of the core of a dying star, when it was actually forged in the core of a dying star,” says Suveen Mathaudhu, a program manager in the materials science division of the U.S. Army Research Office, adjunct materials science professor at NC State and die-hard comics enthusiast. “It’s well documented that the hammer is made out of ‘Uru,’ a fictional metal from Thor’s native realm of Asgard.”

And Mathaudhu can cite documentary sources to back him up. For example, Marvel – which publishes the Thor comics – issued a “Thor’s Hammer” trading card in 1991 that states Mjolnir is made of Uru and weighs precisely 42.3 pounds. That’s lighter than a herd of 300 billion mice, much less a herd of 300 billion elephants. But it raises a different science question.

Using the dimensions and weight on Marvel’s trading card, Mathaudhu estimates that the density of Mjolnir is about 2.13 grams (g) per cubic centimeter (cc). That makes it even lighter than aluminum, which has a density of 2.71 g/cc. So what could possibly be that light and strong?

Mathaudhu has a theory.

“Perhaps Uru is the ‘holy grail’ of high-pressure physics: a form of metallic hydrogen,” Mathaudhu says. “Some predictions of the density of metallic hydrogen fall into this range, it requires extreme conditions to form, and could be a tremendous energy source. It’s thought to be present at the core of planets, such as Jupiter, and at the core of suns – which are stars, after all.”

While Tyson made a mistake in calculating the weight of Thor’s hammer, he succeeded in drawing attention to the sciences of astrophysics and materials science – which is a good thing. For more discussion of Thor, Mjolnir and physics, check out this interesting post on Scientific American’s site about momentum and how Thor can fly.

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  1. I wonder why Neil Tyson was pointing out the weight of the hammer alone. If I thought that the hammer was made from neutron star material, my concern would be the unimaginable way it would explode outside the gravity of the neutron star. Same applies to the Marvel’s mjolnir theory too, something forged in a dying star(under extreme gravity) would not stay the same once the gravity is released.

  2. It amazes me that for all the debate about how heavy or not the Hammer is that people fail to recall a few things. First the Hammer can generate enough force in a direction to propel it on it’s own at extraordinary speeds to the wielder or to propel the wielder (and passenger) along with it. It also receives mental commands at unknown distances allowing it to be retrieved.
    So the Hammer has telepathy in some form allowing it to hear a persons mind and it wielders wishes, it can follow a set of commands and determine a comparison to ideals to determine worthiness in the mind of the holder and from that generate any force necessary to fullfill the requirements of it. The Heart of the dying star part, perfect energy generation to power the device and provide a suitable durable shell to not even scratch as it hits even the hardest of materials in the universe. So they obviously formed the shell with so device within to create the effects given, including chargind particles to create storms and lightning blasts.

  3. “I really wish I had my hammer. Quite unique. It was made FROM this special metal from the heart of a dying star”
    -Thor, from Thor Ragnarok

  4. so basically, a full grown elephant weighs at approximately 7 tons X 300,000,000,000 = 21 Trillion Tons?

  5. The enchantment of Thor’s hammer its not quite simply a magic.The enchantment says anybody who is found worthy will be able to weild it.What I think is that it has some kind of property that allows it to change its gravity.In ‘man of steel’ kryptonians uses some machine to change earths gravity.This hammer is kind of like that,but in miniature self sustaining form.When some one who is not worthy tries to lift it it pulls it down by the same force exerted on it.So as much as force unworthy ones applies on it,it applies as much in opposite direction.Someone worthy tries to lift it they can do it without any difficulty,although only if he could lift 42 pounds,i know that is not a big deal,but even then do you think everyone can throw it or fight with such weigh even if deemed worthy,so only someone with brute strength could use it properly even if he could weild it.What I mentioned above makes it impposible to lift it by whoes not worthy. Let us see to it that Thor would say the real theory or something ,in future one day as he stated he know the theory in Avenger age of ultron.

  6. The enchantment is that nobody who is not worth can lift/wield it. Don’t think of the hammer as something with variable weight. The hammer or its enchantment prevent the non-worthy from wielding it, that is, they find themselves not believing that they can pick it up therefore they don’t, even though they think they are trying to.
    Think of it as a psychosomatic illness, or think of it as (to mix in yet another magic system) an Illusionist spell. If you are convinced the illusionary dragon was breathing a fatal blast, you might well die from it.


    1. What about when it’s just laying on the ground? If it weighed as much as the moon in an area less than 2 square feet it’s going to sink into the ground/bust through the floor

  8. Hi my name is Felipe Uhas, I am 13, and today you spoke at my school at Hesperia Junior High School. but sorry to say thor’s hammer actually weighs as much as 6.7268608 × (10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10 ×10). Why? well in Thor vol. 2, #80 (Aug. 2004). it was created by forging it with the core of a dying star which is also known as a white dwarf star. if you would like to contact me at I am willing to debate and tell you how i got to this conclusion but i would like some help as well.

  9. Let’s look at what we know.

    According to the movies Asgardians aren’t magic. They just have a level of technology so far advanced that it appears magical to us. So it can’t be embedded with some magic spell or enchantment.

    We also know that it can’t be super heavy or it would be crushing things every time it was set down. Tables couldn’t hold it, the helicarrior wouldn’t be able to take off and so on. Even if Thor could lift a super massive hammer how would he move around? Every time he stepped on something if would crumble beneath the weight of the hammer he holds.

    But we also know that Thor isn’t the only one who can wield it and the hammer chooses who can wield it. So far in the movies Thor isn’t the only one who is able to move it (I won’t spoil it by saying who or under what circumstances).

    Based on that we have to assume the hammer is a technologically advanced machine that has some awareness of who is touching it and can control it’s physical properties based on who that is. It must have some default mass that is not on the scale of billions of elephants because it can be set down without crushing things. It also must be able to change that mass to be exactly equal and opposite the force exerted on it by the unworthy. That explains why only the worthy can lift it but yet it doesn’t crush things otherwise.

  10. As much as I thought NDT’s explanation was cool, I have to side with the “42 lbs., but enchanted” answer.
    For one thing, the crater it makes when it lands on Earth in the first Thor Movie would be more commensurate with a 42 lb. object moving at astronomical speeds. If Mjolnïr weighed as much as 300 billion elephants it would’ve obliterated the entire planet.
    Secondly, we all know that “42” is the answer to The Great Question of Life, the Universe, and Everything, so it’s not unreasonable to think that a demigod’s primary source of power would involve that number somehow (yes, I’m aware that I’m mixing two different franchises – so sue me).

  11. THOR is much more powerful than the Hulk , if THOR wanted he could crush the Hulk ! The Hammer can only be moved by THOR and His Father ODIN .

  12. and also, to digritz, no one “unworthy” has lifted the hammer, period.

    The hammer is NOT super heavy, that only becomes light when someone worthy picks it. The Hammer is a judge of character. Odin spoke an enchantment into it, it has nothing to do with weight, so stop trying to explain it as super dense, when that has nothing to do with it, yeesh guys. All you smarty pants just look, well, ignorant.

  13. and for Franks comment, you are wrong. Thor can lift it cause he is worthy. Not due to his belt of strength, which has nothing to do with Mjolnir, or his powers. Hulk has never lifted it before, not canonically.

  14. Lol at all the people trying to explain it with science. It doesn’t matter. It was a hammer forged in the heart of a dying star. A hammer. Odin spoke the enchantment into it, stating only those worthy can lift it.

    He spoke the enchantment into it. This is the same guy who stripped Thor of his powers with a thought. Explain that with science. It has nothing to do with science, and physics. Due to the enchantment, the Hammer is a judge of character, and has a special bond with Thor, or one who can wield it, and can be summoned with a thought. It doesn’t need to be explained scientifically, when the hammer was given these properties by a vocal statement, by a man who was able to strip the Thunder God of his powers with a mere thought. No science here, it can’t be explained by science, just pure fictional divinity.

  15. You guys must not actually read much. Only Thor can wield the hammer, not even Odin can hold it with or without enchantment. However the only reason why Thor can is because he was given a magical belt which give him the ability to use it. Hulk can and has picked it up before but he isn’t able to just do as be pleases and swing it around like Thor can.

  16. Science and Thor’s hammer fine. I got no problem with that. The difference “Forged of a dying ” and “In a dying star” would seem to be totally irrelevant.

    If a material is forged at the heart of a dying star it could most certainly take on the aspects of the environment it is forged in. In this case incredible pressure. Now I can see a demigod being able to handle this but the material being forged. I don’t care if it’s Uru, Aluminum or bird shit. It’s going to be dense and as heavy as the atmosphere it is created in. Unless you add in magic. Then you can throw any and every theory out the window no matter how many degrees follow the name.

    Please remember that a star doesn’t start out as dense as it becomes when it’s dying or dead. IT’S MADE OF GAS! How does it become so heavy…. PRESSURE!

    Also one final thought there are others that have in fact picked up the hammer who were clearly unworthy. But it wasn’t easy which means it has another component aside from the enchantment. IT’S HEAVY!

    Materials scientist my rear end.

  17. Why even go with ‘magic’?

    We have quantum theory!

    Let’s look at it this way: Physics at the core of a star is a bit different than what we’re used to when taking a walk through the park.

    On one hand, the ‘metal’ of the hammer could be as deGrasse Tyson describes or as can be found in most Stephen Baxter novels: ‘Densely packed neutrons’ or ‘neutron star matter’. This would make it the most dense substance we can imagine outside of a black hole and would indeed weigh an enormous amount and be impossible to lift in Earth gravity (Heck, it would take an enormous amount of energy just to get it moving in vacuum outside of any gravity well).

    On the other hand, the metal could be ‘metallic hydrogen’. This would explain the lightning, right?

    But what if, as Tevye said, “There IS no other hand!”? What if the Hammer, being forged of material from the core of a star where particles behave *very* strangely, exists in BOTH states at once?
    Or, more appropriate to the circumstances, exists in one state for some, and another state for others.

    When Thor picks up Mjolnir, his perception resolves its quantum state as metallic hydrogen. Same goes for the ground it is on or the table upon which Thor rests it (thus not punching a hole straight through the mantle to the Earth’s core). Lightning? Sure! As far as we know, metallic hydrogen may be very energetic.

    When the ‘unworthy’ attempt to lift it, however, its quantum state resolves into a neutron mass, becoming immovable for *that* individual.

    Let’s even pretend that Thor, son of the All-Father Odin, can *manipulate* its quantum state. According to quantum theory, quantum states are manipulated by observation, and we might assume that a god could get a handle on that. That way he can easily swing it, and then while in relative motion impart great mass to it which would easily lift him skyward. Sure, that’s seriously cheating physics, but quantum mechanics kinda does that already… just on a much, much smaller scale.
    Indeed, existing in two states at once would explain why Mjolnir itself can sit gently on the ground while the one who attempts to lift it sinks into the earth.
    It would also mean that when Thor decides to strike something with it, it can do so with the force of “300 billion elephants”… pretty much what it would take to make an Incredible Hulk reel.

    So, thanks to the phenomenon of quantum theory, Mjolnir would work like magic in the hands of one who could manipulate its quantum state, while for very specific ‘unworthy’ sorts, they would indeed be trying to lift Neil deGrasse Tyson’s “Herd of 300 billion Elephants.

    1. You said EXACTLY what I was thinking, almost verbatim as I thought in my head. This is by far the BEST answer, IMO.

      Just as particle/wave motion of electrons is somehow determined by viewer perspective (observance), somehow, some observer, either the wielder, Odin’s enchantment, or the hammer itself “observes” and deems worthiness or the lack thereof and behaves appropriately per the “rules” allowing or disallowing the hammer to be manipulated.


  18. Did anyone think to ask what the carrying capacity of the SHIELD Helicarrier is when fully loaded? I’m no scientist, but I think the fact that the Helicarriar was in flight through Thor’s entire time on board, this might suggest a fallacy in the logic of 300 billion elephants, which works out to about two trillion tons.

  19. “The only way of discovering the limits of the possible is to venture a little way past them into the impossible.” – Arthur C. Clarke (Profiles of the Future, 1973)

    “Well… magic’s just science that we don’t understand yet; Arthur C. Clarke” – Jane Foster (Thor, 2011)

    Wow… my mind is blown that everybody is onto this, but mostly that NDTyson took the time to read, consider and post; This is the highlight of my year. I should point out that he does not “stand corrected”. His tweet started with “If”, so it really doesn’t matter what he’s saying it’s made of; it wouldn’t necessarily be wrong. As David Pizarro states, the burden of proof doesn’t necessarily fall on either one of us. The conjecture and discussion is a truckload of fun, but I suppose it depends on how much a truckload really weighs.

  20. Actually Thor’s Hammer is Zero Mass. Because this Rule: A/0=/A. Thus g/m=a or g/0=/g thus a=/g which means as a zero mass object Thor’s hammer is exerted on by /gravity (a gravity not of this universe).

    So out there is a particle of zero mass with an acceleration of /g.

  21. According to Norse mythology, the hammer was created by the dwarves, and the type & source of the metal was never really discussed. In the comics, “uru” is a metal found in Asgard – In one mid-1960’s issue, Thor is seen carving a substitute hammer out of a cliffside, which would indicate that the cliff was either a very pure vein of uru, or that the writing was very sloppy… But the lore of the comic is not that the hammer is heavy (and only Thor is strong enough to lift it), it tells us that Odin’s enchantment makes it to that only those WORTHY can lift the hammer. That’s why the Hulk can’t lift it, even though his strength is equal to or greater than Thor’s, but the alien Beta Ray Bill was able to easily heft the hammer. The comics have been maddeningly inconsistent as to whether machines can lift it, although if Thor leaves the hammer on a table, the table won’t collapse.
    Hope that helps!
    Tom Harris
    (Host of the Radio Free Asgard podcast)

  22. I don’t know if the burden is suddenly on Prof. Mathaudhu to explain the supernatural behavior of Mjolnir (such as the Hulk’s–or anyone else’s–inability to lift it), any more than the burden would have been on Prof. Tyson to explain Thor’s ability to lift something as heavy as 300 billion elephants. Suspension of disbelief might be psychologically easier when it’s ONE guy lifting something that heavy, but both cases require some serious flexibility in the laws of physics. The only question is which laws are being bent in the Marvel Universe.

    That said, the fact that Prof. Tyson took the time to comment on this is AWESOME (that man should be president). I know Prof. Mathaudhu (well enough to spell his name without cheating), and I suspect his reaction is the same.

  23. My degrees are in the arts but I will propose that the ability to move Thor’s hammer is magic… But I’d refuse to suggest that magic is scientifically uninteresting and may be especially relevant to areas of cosmology which have reached at concepts like the holographic nature of consciousness, a rather magical concept.

    Mathaudhu’s ideas seem pretty sound to me when it comes to the physical nature of the hammer. Keep in mind, the ability to lift the hammer is not limited to strength and fairly frail people have lifted it. The worthiness is tied to the spell and is about the beliefs, intent, and nature of the wielder; Thor’s strength doesn’t enable him to lift the hammer (it’s not especially heavy) but the spell prohibits other people from lifting it.

    But my own — totally casual — perspective on the spell and magic in general (and this may be nonsense):

    The hammer is contained in a closed space-like curve. Within this curve are alternate laws of physics (just as Star Trek warp bubbles defy physics and closed time-like curves defy normal rules of causality). The spell is a closed space-like curve and since the parameters of this spell are variable (ie. situational) then an outside force most likely continually monitors or adjusts the space-like curve or the hammer itself contains an artificial intelligence and a power source capable of modulating the space-like curve. (Or perhaps someone with an outside perspective of causality created a regression for the necessary space-like curve that would cause the laws of physics of the hammer to constantly vary but happen to be immobile at the chronological points where someone unworthy would attempt to lift it; if you can predict when the wrong person attempts to lift it, you can time the physical properties of the hammer to render it unliftable at those moments.)

    Likewise, the spells of someone like Doctor Strange may involve some kind of telekinetic or perception based geodesic manipulation to create highly specialized space-like curves. Effectively, it’s just creating special physical laws that apply in a localized region… and the tricky part is making those laws specific enough to adapt to desired contexts.

    So going with classic myth, a love spell (such as the kind the Enchantress uses) may simply be triggering special physical laws which cause the hypothalamus of a person to physically trigger certain chemical secretions by having it respond according to an internally consistent set of stimulii. For example, perhaps certain synapses have increased conductivity when other synapses are triggered as a special case of closed space-like curves in the brain.

    Basically, though, it’s just creating situational laws of physics that are more nuanced than the laws of physics in the external world.

    Just a thought, anyway.

  24. I don’t know if the burden is suddenly on Prof. Mathaudhu to explain the supernatural behavior of Mjolnir (such as the Hulk’s–or anyone else’s–inability to lift it), any more than the burden would have been on Prof. Tyson to explain Thor’s ability to lift something as heavy as 300 billion elephants. Suspension of disbelief might be psychologically easier when it’s ONE guy lifting something that heavy, but both cases require some serious flexibility in the laws of physics. The only question is which laws are being bent in the Marvel Universe.

    That said, the fact that Prof. Tyson took the time to comment on this is AWESOME (that man should be president). I know Prof. Mathaudhu (well enough to spell his name without cheating), and I suspect his reaction is the same.

  25. “”Whosoever holds this hammer, if he be worthy, shall possess the power of Thor.” is the inscription on the side, placed there by Odin. Hulk is not worthy, therefore he cannot lift it. It has nothing to do with weight or strength. It is an enchantment.

    1. The hammer sense who is picking it up, and decides if they are deemed worthy, unless your are so powerful you can overpower it. But once it decides who is worthy, if they are worthy it should weigh around 42 pounds, but if they are not, it decides how much it wants to weigh

        1. But surely it is impossible for any material to change its weight because weight is proportional to gravitational field strength so surely Odins magic doesn’t make the hammer change weight but it simply does not act upon their will

  26. I could have sworn I heard the fellow in the recent Thor movie say that Mjolnir was forged **of** the material of a dying star. If not, I stand corrected. And, I suppose, even if he did say what I thought, I stand corrected — I gladly defer (as should we all) to hard-core Comic Book people. But now you’re stuck making up all kinds of supernatural forces to account for the behavior of what is otherwise an obviously heavy object that even the Hulk can’t lift.
    -NDTyson, NYC.

    1. That’s exactly what makes my brain ping ping ping when I try to explain how it can be forged “in the heart” or “of the heart” of a dying star if I remember correctly, those are some astronomical pressures and temperatures. Any stars core with the needed 10 to 20 solar masses to make heavier elements can’t be duplicated anywhere But; in a dying star! Now, I’m thinking that Thors ancestors learned how fuse, collect and change neutrinos into a type of compressed metal. I imagine if they could do that, then it would have magical abilities like in the comics; but it’s all theories…

    2. All of you should check real Norse Mythology stories. It is said that two dwarven brothers forged it with Loki trying to stop them.

    3. Yes, you’re correct Thor did say that in “Thor: Ragnarok”, however the Marvel Cinematic Universe (Earth-199,999) is not the same the Primary Marvel Universe (Earth-616), and in the comics it was created IN the heart of a dying star WITH Uru which was later enchanted by Odin. It could be that in the MCU it is created from neutron star material but it’s probably more likely that Thor himself was wrong as the gravitational pull of his hammer would be close to that of a black hole, people around him would have their body parts sucked in at different velocities and would literally be shredded. You’re a physicist so I’m sure you know more about this than me. This has not been shown to happen in the MCU and not to mention that with that much pressure on the surface of ANY planet (Earth or Sakaar) it would surely sink to the inner core of the planet. Another thing that has not been shown to happen.

    1. One theory is that when someone other than Thor tries to lift it, it emits more and more gravitons, increasing its weight drastically and making it appear as though it’s really heavy. Theoretically the Hulk COULD lift it if his strength increase factor outmatched Mjolnir’s graviton emission rate then he should be able to lift it. However from what we’ve seen that’s never been the case.

  27. Its a MAGIC hammer. it MAGICALLY decides whos worthy enough to pick it up. the Hulk can easily become stronger than thor and still not pick it up.

    Whats this talk about science backing a marvel comic book?

  28. Thors hammer can only be lifted by those who are worthy…that being said you have to add magic in this equation (this is based on the comic right?). For those who are worthy, it could weight 42 pounds but for those who arent….it could be Neil’s answer so good luck lifting that