The worldbuilder's double-sucker-punch: the cubed-square law and atmospheric hypoxia.

They suck because now you can't (realistically) have giant metal robots or terrestrial monsters the size of skyscrapers. About the biggest monster we could get is something the size of a Brontosaurus. In modern days, it's something the size of an elephant.

But what about AQUATIC monsters?

We know that things under water tend to grow much much bigger because they don't have to support their own weight. The largest elephant on record weighs somewhere around 12 tons. An average blue whale weighs about 100 tons, with the real monster whales busting the scales at over 170 tons.

Under our earth's gravity and atmosphere, how much bigger can we go? Somebody please tell me that the oceans of my earth-like planet could be teeming with Kraken-sized kritters and Cthulu-sized terrors. How big can we go before physics starts writing us a ticket?

  • $\begingroup$ I'm just going to point out here that it's not going to be a monster in any sense of the word but 'large' because the large aquatic creatures also tend to be the docile ones, the notable exceptions being the toothed whales, who are still smaller than their cousins the baleen whales. $\endgroup$
    – Halfthawed
    Apr 30, 2020 at 23:05

1 Answer 1


Beating the square-cube law it's easy: just allow the surface to grow at a good ratio of the volume. Go distributed and/or go flat and/or get a fractal 'skin' surface.


  1. supercolonies - ant, bees, coral
  2. clonal colonies - Pando - the trembling giant, Oregon humongous fungus.

Are they monsters? They are certainly big.
And they are able to do damage? I don't think the trees invaded by the fungus are happy. See (or watch) also The Swarm for a potential example of how fast the damage can be exacted.

Now, how big? How about a coral supraorganism the size of Europa, with the energy obtained from the tidal heating?

Will they develop a nervous system? I suppose that's not impossible, even if there will be no "brain" (as the centralized location of "processing", but a distributed/diffuse one. With nodes resembling an octopus'es brain (scroll to "The ‘Brain’ of Cephalopods – An Outline and a Summary of Novelties"):

In the octopus, as far other cephalopod species, the ‘brain’ is assembled through a series of ganglia of molluscan origin to form lobes that are fused together into masses

interconnected by dense (still distributed) networks like the enteric nervous system (that second brain that gives one "the feeling of guts").

Will they develop intelligence? Very likely, although their intelligence is unlikely to be comprehended by a human intelligence. Because an intelligence is formed by the direct experience in the interaction with the environment and one must admit that the two ways of sensing/interacting with the environment (human/monster) differ too much.

Will it develop technology? Unlikely. Too adapted to its/their environment, there's hardly any evolutionary pressure to drive towards the technology.

But assuming it does, I don't want to think of a conflict between Earth and a planetoid sized organism, able to move the hosting rock through interstellar space to get here.
But maybe you, the hard SciFi author, are tempted to think about it?


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