I went to go see The Incredible Hulk. I liked the Hulk since I was a kid. I think I was a fan of the TV series then later stumbled into the comic book. The Hulk is not realistic by any stretch of the imagination. Complex mammals like humans die when exposed to high levels of gamma radiation, nor is it likely to achieve such an amazing transformation.
But one thing made me laugh during the movie was the Hulk’s weight.
I know, I know — it’s a comic book. But being a science geek, I can’t help but notice this stuff.:-)
At first, it seemed obvious that the Hulk was heavier than Bruce Banner. Then a scene on a medical table clinches it when Banner does his transformation, and the table buckles underneath him. A table which can usually handle 200+ kg easily. But where the hell does that extra mass come from? The movie makes it quite clear it’s gamma-radiation fueled metamorphosis, but still: gamma radiation to mass?
One kilogram of mass is the equivalent of 8.98755179 × 1016 joules (or roughly 19 megatonnes of kilogram of TNT). Assuming 100% effeciency in conversion of course. (HA! As if…) But to get 1 kg of mass, that means Bruce Banner, weighing in at 128 lbs (according to the Marvel database), absorbed at least 1.5 × 1015 grays of radiation (1 gray = 1 J / kg). Doesn’t mean much, huh? Let’s change the numbers around ala Wikipedia to sieverts (Sv) so we can look up the effects. From what I can tell:
1.54798125 × 1015 grays * 1 (for Gamma radiation) = 1.54798125 × 1015 Sv ≈ 1 547 981 250 000 000 Sv
(this is a very rough estimate based on the idea Dr. Banner received a full body dose, if we were talking about a portion of his brain, then the numbers go up… a LOT!)
According to Wikipedia, the highest known dose was in the 100 – 180 Sv range, and each of the victims died. Of course they go to great pains to emphasise how lethal that radiation dose was in the movie and comic books, but still: 1.5 million gigajoules of energy per kilogram of his body. 336 megatonnes of TNT per kilgoram of his body. He wouldn’t have died—he would have vaporized! And that’s just to get one extra kilogram of mass.
Obviously, the extra mass must be coming from somewhere else, and it has to be denser than the air around him. If he was absorbing air, then his net buoyancy in the atmosphere would not affect his weight—exactly like inflating a balloon doesn’t increase its weight. So I gotta ask: where does the Hulk get his bulk? (pun intended)
P.S. If Banner did have protein bars stashed on him, then his weight still weigh the same since the bars are on his person.
P.P.S. No, I don’t have better things to do—it’s too dang hot here in Vancouver to sleep!! 🙂
Sci-Fi Science Blunders Hall of Infamy 
I like the read, but here and there I like it less, and the pun-intended-part is just too much.
http://www.thebestpageintheuniverse.net/c.cgi?u=puns
By: rick on November 2, 2008
at 2:40 pm
Rick: “the pun-intended-part is just too much.”
Tough! It’s my blog and I can pun if I want to. 🙂
By: movieotaku on November 2, 2008
at 4:06 pm
Perhaps the radiation triggered a chemical reaction with the outside air and some bodily substances that compressed the air into a much denser material.
By: Ctesibius on June 22, 2009
at 6:16 pm
I thought about that at the time, but I think we would have noticed the sudden rush of wind as 1000+ kg of air was suddenly metabolized and fixed, about 833 cubic meters of air would be displaced (about a 1/3 of an Olympic-size swimming pool).
(How I calculated the amount of air for 1000kg is left as an exercise for the reader ;-))
By: movieotaku on June 23, 2009
at 3:25 pm
“where does the Hulk get his bulk? (pun intended)”
I don’t get it, where is the pun?
By: Yaba on September 28, 2009
at 8:49 am
well, apparently in the Hulk show, he transforms biologically not in physic. So instead of killing him, the radiation transform his cells/dna so that the cell can rapidly multiply faster than usual and then gets back to one cell in the next moment. :p
when watching scifi like this, its not much of a science, its more like a fiction. So we have to assume everything shown as facts and then try to come up with theories to prove its correctness, it is by this approach that scifi may become non-fiction one day, like how star war predicted space travel 🙂
By: mtsen on March 7, 2010
at 2:16 pm
We all watch Bruce Banner grow into the Hulk with his anger/accelerated heart beat. Its obvious that he gains tons of strength and stamina when the change occurs. Strength comes from muscle. Muscle weighs more than fat/normal tissue. So watching a relatively small man change into a behemoth of muscle, one can assume that the change affected his muscles, making him much heavier. Don’t think of it as him changing into something else, think of it as him growing into something else very rapidly. IE, if 150 pound man works out for months and puts on 30 pounds of muscle, he is now 180 pounds. Same concept…at least I think it is…
By: Jofus on June 5, 2010
at 11:46 am
I think the Hulk’s extra mass comes from water. Humans are 70-90+ percent water depending on who’s figures you believe. The atmostphere is full of water ergo it’s not such a stretch. Granted this has a similar problem to your massive instant vacuum null-hypothesis.
In the first movie with Eric Bana, when he turns back into Banner, a TON of steam pours off of him and water pours out of him. This tells me that yes water is a huge part of his mass and his transformation back is exothermic. This explains the speed differences in his transformation depending on where he is and the levels of ambient moisture in the atmosphere.
By: Brent on September 17, 2010
at 9:47 am
This is just my take on it:
When we get angry our bodies release energy so that our fight or flight response can work at optimum efficiency.
In the case of the Hulk that energy is combined with the stored energy that the gamma blast triggered in his cells.
You see, Bruce is not radioactive, just an artificially enhanced mutant. His mutation is the ability to store and convert energy to mass. Normally he would have found that he felt at his peak of health on a sunny day. A bit like superman, by on mortal terms.
The radioactive burst just enhanced that ability so now any energy his body produces triggers the energy stored in his body to multiply by his anger, and then to invert back on its self on a quantum level, that then gets turned into a bulk that mimics the surrounding tissues. Thus every river in his body is enhanced to the super human level.
The conversion back is an exact reverse of the change. His body absorbs all that energy back into his cells.
Oh yeah, his mutation allows for the storage of all that energy without negative effects due to the quantum mechanics of his cellular structure.
Like I said just my take on the whole Hulk/bulk problem.
By: Jason Mackinnon on December 20, 2011
at 3:26 am
According to the “official” explaination, he’s drawing mass from an extradimensional source to grow, and it returns there when he goes back to Banner.
Another explaination might be the energy being converted to mass might be from directly tapping superstring energy, kinda like the goofy ZPM’s in Stargate Atlantis…
By: Valandar on May 30, 2012
at 4:27 pm
How come no one has suggested dark matter if he could interact somehow with dark matter this would be easily explained. The fact is we can’t account for most of the energy or mass created by the big bang maybe he’s drawing from that
By: flibbleking on December 17, 2012
at 12:14 am
Because there is no such thing as dark matter or dark energy. I suggest that it is an internal energy form that is stored in his cells that is triggered by his rage, and the residual radiation starts the transformation. It then feeds off ambient energy, including the kinetic energy of objects hitting him, and transforms that into mass.
By: jasmack1972 on December 17, 2012
at 11:56 am