I think the point is, what affects that ‘some point’ where weight gets too big? Obviously, having a liquid environment helps - does the liquid density matter? Gravity? Local condition absolutely matters - now, maybe his goal of way-way-way big is impossible, but I’d want a cite that Earth has absolutely ideal conditions for large-scale life, and there’s nothing bigger out there.
Well, it has some to do with local conditions. One of the reasons we don’t have gigantic jurassic sized mosquitoes anymore is that the concentration of oxygen in the atmosphere is much lower now. Bugs don’t have lungs, they have spiracles, so to get big they need a higher percentage of oxygen. Cite.
An interesting corollary to this question is “why don’t we have megafauna on Earth?” Part of the answer is the square-cube relation, but that obviously isn’t the whole answer. The ratio of a volume to its surface area wasn’t any different when dinosaurs roamed the Earth, but we did have gigantosauruses. What’s up with that? Another possible explanation is Darwinian. Small animals just out compete big animals, and that’s why people are people-sized and not as big as a house.* Of course, gigantic animals didn’t just appear one day, so they must have had some competitive advantage versus the smaller animals in order to evolve in the first place.
My guess is that the answer is that climate and luck both play large roles in what kind of animals are present. In the Mesozoic era there was a lot of oxygen in the atmosphere, and it was relatively easier to get big. I’m not an expert in this kind of thing by any means, so I can’t speculate on the answers, but I don’t think it’s a priori a stupid question to ask. (Otherwise I wouldn’t ask it. 
)
- If people were as big as houses, what would they live in?!
Uh, yes, I did read the article and mercy me, I even understood it—in fact, it wasn’t even an alien concept to me before your posting the link. I’m not suggesting that the square-cube law can be rendered null and void under the right conditions, I’m certain it applies across the board, from one end of the universe to the other. It’s as inescapable as gravity. I do, however, posit that the law’s effect on the ultimate size of creatures will vary depending on local conditions. Heck, we see its variable effect on life forms right here on earth (e.g. insects can’t grow as large as mammals; land creatures can’t generally grow as large as water-bound creatures, etc), why would we not expect even greater variability of the effects of the square-cube rule on biospheres with even more profound changes in planetary and biological conditions?
I’m not sure about a reducerizer, but we’re probably not far off from discovering and being able to accurately manipulate genes responsible for organism size. And this may ultimately be the answer to the problem of bringing large endangered carnivores back from the brink of extinction. By genetically manipulating the Bengal Tiger down to the size of a hamster, my house alone could probably serve as a viable habitat for the entire species. And, watching the tiny felines stalk, ambush and administer the tracheal coup de grass on vermin mice would be worth the price of admission (not to mention the satisfaction of sending a diminutive Grizzly Bear off to silence our neighbor’s yappy miniature poodle). Alas, when we terraform new planets, regaining large bestial habitats, we simply genetically engineer our petite carnivores back to their original size.
…On second thought, why limit ourselves to miniaturizing only the carnivores?
I must confess some type of vulgar hedonistic delight at the thought of eating a hamburger patty made from an entire cow. Finally, McDonald’s may retire its weary ad campaign, claiming 100 billion hamburgers served for the much catchier, 100 billion bovine butchered.
(…Yes, they need me on Madison Avenue…)
…And, don’t even get me started on* Pigs in a Blanket* hors d’œuvres—with a whole little piggy carcass in each blanket…*mmm…mmm…good!
*
Minnows as large as blue whales would be a hell of a lot more than $2.99 per dozen at the local bait shop…
Or you’d just use the BIG dollar bills.
I think you mean “living creatures can make in themselves”, in which case I wouldn’t put it out of the realms of possibility for there to be creatures with a buckytube skeleton and diamond joint bearings somewhere. But it’d have to be a pretty high-energy environment, IMO. We’d probably see it as a hell-planet.
Me, I’d say the OP’s question leaves out something - what fills the smaller niches? Are even the bacteria upsized - say, mouse-sized? Something will fill the smaller niches then.
Anyway, I don’t think size works that way. In addition to the square cube law, there’s things like the properties of water etc. to look at, and those are pretty universal. It’s true you can do funky things with hydrogen and other molecules at high T&P (See the excellent Hal Clement stories Mission of Gravity and Close to Critical), but any universal solvent, whether H[sub]2[/sub]O or H[sub]2[/sub], is going to fall foul of the size issue at some point. And something swimming in H[sub]2[/sub] isn’t a minnow, anyway.
Well, if you scale gravity inversely to size, it cancels out the additional power – make something 10 times as big, it gets 1000 times heavier, its bones only a 100 times stronger; but if that thing exists in gravity 1/10 of that on the Earth, its weight is only 100 times that of its smaller-sized and earthbound version. Of course, lowering gravity is capped by the need of holding on to some form of atmosphere.
Regarding individual cells, though, I can’t imagine that those would scale up well – think, for instance, about nutrient transport: if you scale a cell up by a factor, the rate of transport through the cell walls scales with the square, while the volume that needs to receive whatever is being transported scales with the cube of that factor.
How about a huge, slow-moving, balloon-like, “liquatic” creature with a high-tensile-strength membranous skin wrapped around a hyper-elastic, buckyball- latticed, “cartilaginous” skeleton, with a super-efficient metabolism that extracts energy and constituent organic building blocks, in baleen-siphoning fashion, from its large, non-massive planet’s abundant, free-floating, plankton-like food supply?
…oh, wait…I just described my mother-in-law…