I'll start by saying that whilst my scientific knowledge is pretty basic (if ever-increasing) it would be good to hear answers that can give a layman's summation as well as a more scientific explanation, if that's possible.

So: all changes in matter must be exothermic or endothermic, and the question is pretty much as written - for example, it seems to me that the Incredible Hulk's rapid change in size (or that of any fictional shapeshifter for that matter) would have to have an enormous corresponding release or intake of energy which would realistically cause them to either combust or flash freeze. If anyone is smart enough to deduce which it would likely be, I'd love to see the deduction.

Bonus points for an explanation of why that never seems to be a problem for any of these beings (even if the fully realistic answer is 'because the writers ignore it.)

Edit for world-building clarity - I have used the Hulk as an obvious pop-culture creature that everyone is aware of, and one that specifically changes scale dramatically. The question could be applied to any and all shapeshifting creatures though, and I'm aiming to find a realistic way to represent this or work around it within my fiction. Even if the answer does just end up being 'magic', I would still like to have a real-world factual basis to work from.

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    $\begingroup$ Welcome to Worldbuilding.SE! Questions about existing universes are off-topic here; this site is strictly for building new universes. If you want an in-universe explanation for whether Hulk's transformation is endothermic or exothermic, you can ask on SciFi.SE. $\endgroup$
    – F1Krazy
    Commented Sep 10, 2022 at 12:51
  • $\begingroup$ I agree with @F1Krazy. This question should be on SciFi.SE. $\endgroup$ Commented Sep 10, 2022 at 13:29
  • $\begingroup$ I suppose I should have been clearer in that I would be using this answer to worldbuild creatures with similar abilities, the Hulk was just the most obvious parallel I could think of in pop-culture. Was also not aware of SciFi.SE so I shall ask there too :) $\endgroup$
    – Morthane
    Commented Sep 10, 2022 at 17:41

1 Answer 1


It can't be neither of the two, because if it was one of the two transitions would happen spontaneously, while usually shapeshifting happens at will in both ways.

My hypothesis is that the two versions of a shapeshifter are two metastable states with same energy content.

enter image description here

Shapeshifting simply needs the transition from one state to the other to be activated, and it is the moment when the shapeshifter does the patented gesture.

  • $\begingroup$ Hmm that's interesting - I'll have to look into that in more detail, I don't think I have the knowledge yet to comprehend what's being talked about in the thread, but I think I get the idea. My thought with the question was if we continue using the hulk as reference, I was picturing the human-sized mass expanding due to the breaking of chemical bonds, and then shrinking back as bonds are formed, but then something like ice or some metals expands as bonds form on freezing instead. Obviously I have the base knowledge to think of a question, but not enough to know if what I'm asking is dumb XD $\endgroup$
    – Morthane
    Commented Sep 10, 2022 at 19:25

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