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How big can an animal get? What size is implausible?

Posted: Tue Feb 07, 2012 8:27 pm
by munsterspeek
A lot of sci-fi does giant monsters, and just assumes they will be giant versions of the same thing. Going back to Them! and other radioactive monsters like Godzilla, Hollywood movies often size up something and then throw it up on the screen. You can even see this in Cloverfield and to some extent the recent Norwegian film The Troll Hunter.

I think the real science would be more interesting.

I wonder what sort of physics are involved. There is a lot of scientists already blogging or even submitting papers about this, maybe one of them would make a good guest? Does anyone know someone who would be a good guest for the show? ... HI6mUP8_5Q

I think it tails well, too, into the real scientific question: what is the upper size limit on animals?

Apatosaurus, for instance, has very special physical adaptations. The ideas of them "swimming" in swamps using their long necks to "snorkle" in deep water which is physically, I am told, problematic, but it used to be a common to hear scientist speculate on that. I've heard there were periods of time with higher levels of oxygen in the atmosphere that produced ( or allowed for ) giant snakes and so on.

Speaking skeptically, I read some crazy theories on years ago about the constant of gravity changing over time to allow for some of the larger dinosaurs.

Some topics I'd like to know more about:

Why, specifically, allows whales and other sea animals getting larger than land animals?
What about Dwarfism on islands ( mini mammoths ) vs. giantism on islands ( giant birds or the komodo dragon )? What are the evolutionary forces that drive each option?
Is there an upper size limit for insects and arthropods?
Has nuclear fallout or radiation ever produced giants of any type?
What forces do produce giants?

Re: How big can an animal get? What size is implausible?

Posted: Tue Feb 07, 2012 8:34 pm
by Gawdzilla Sama
Seismosaurus has led to speculation of 300 ton dinos.

Re: How big can an animal get? What size is implausible?

Posted: Tue Feb 07, 2012 10:17 pm
by Hex
I've heard of the oxygen problem. The more oxygen in the air the easier it is to circulate it throughout the body making larger animals to easily process oxygen than we have to today.

I've also heard about gravity in the water vs. gravity on land. Though they are the same, creatures that live in the ocean have buoyancy to help counteract the effects of gravity.

This explains that and more, better than I could.

Re: How big can an animal get? What size is implausible?

Posted: Wed Feb 08, 2017 2:31 pm
by Kevin Levites
Isaac Asimov wrote a wonderful essay on this exact topic, as he was called to task by his fans for writing Fantastic Voyage, which was a novel adaption of the movie with the same name.

I'll summarize his arguments, but in my own words.

If we suppose that I--who weighs about 200 lbs. and stands 6 ft. tall--was blown up in size to about 70 ft. tall (like in the television series Land of the Giants), there are a lot of negative consequences to my health.

Surface area increases as the square, while volume increases as the cube--this was pointed out by Gallileo 4 centuries ago.

This would mean that I would have about 1/12 of the surface area in my lungs, so it would be like having bad emphysema. I suspect that only a high-pressure dive chamber could keep me breathing.

My intestines would have only 1/12 of the area, so I would have to eat 36 meals a day to keep from starvivg.

My kidneys would only have 1/12 of the area in their tubules, so I would need to be on dialysis.

I would only have 1/12 of the skin surface area relative to body mass, so heat would build up quickly. I would probably have to live in arctic waters like a whale to keep cool.

If I tried to stand up from a seated position, my legs would snap like toothpicks because bone strength is a function of cross-section, and cross-section is a function of area.

To top it all off, consider my brain under these circumstances. Intelligence is attributed to the cerebral cortext, which is folded and convoluted to give it more area.

My brain would not have enough surface area to maintain intelligence, so I would probably be severely handicapped...probably like a bad microcephalic.

This even happens in real life. Alzheimer's disease can cause the convolutions of the brain to smooth out, and functional decline is closely correlated with this progression.

All of these points apply--in a different form-- to any living thing.

The only way a giant tarantula from the movies could kill you is if it falls on you when it dies.

Re: How big can an animal get? What size is implausible?

Posted: Wed Feb 08, 2017 2:37 pm
by bobbo_the_Pragmatist
Large animals could be flat rather thin blobs with distributed nervous system.

Think Rush Limbaugh.

Re: How big can an animal get? What size is implausible?

Posted: Wed Feb 08, 2017 2:50 pm
by Kevin Levites

There are ways around these issues.

If I was to design a giant animal (I am, after all, a professional science fiction writer), I might have it live in the water, and have two (or three...or more?) complete sets of redundant organs equally distributed along its length.

I would have more than one brain, because nerve impulses from the tail would take too much time to propogate themselves all the way to the brain. This is not exactly original, as some of the large, sauropod dinosaurs had nerve ganglions in their spines so that they could thrash their tails before the tiny brain knew about the situation.

Humans actually have something very similar, and for similar reasons.

Have you ever seen a picture in an anatomy course of a person snatching their hand away from the candle flame as an automatic response? The impulse goes to the spinal cord and travels right back without reaching the brain.

My huge animal would have to be a filter feeder, constantly swimming so that it could scoop plankton into its ever-hungry maw.

And so on.

Re: How big can an animal get? What size is implausible?

Posted: Wed Feb 08, 2017 6:36 pm
by ElectricMonk
Does it have to be an animal?

In a forest in Oregon, there is a fungus that covers 2,200 acres.

Re: How big can an animal get? What size is implausible?

Posted: Mon May 21, 2018 4:39 pm
by Bobbie the Pragmatist
What I don't like in the movies is the inconsistency of the size of the same character creature/monster. You can look up the height of King Kong, for instance, in the 1933 version. Then, compare that to his much greater height that I believe I can see when he battles Godzilla.