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I don't know how the dinosaurs did it, but I still don't see much of a reason to believe the earth has become more massive. It should be the same mass it was millions of years ago.

But dinosaurs must have been pretty powerful creatures. With more power, as it is recognized in physics, there is more applicable force, and therefore more acceleration. So if they were strong enough to counteract the disadvantages of their mass, they should have been fine. And I think they would have evolved with strong enough bodily structures as to avoid being crushed by their own weight.

Interesting thought, though.

No problem.


That's... hm. Well, let's just go to the reasoning.


I'm willing to bet that most elephants are faster than you are. That's not some slight against you, please understand--few people could. You're right that elephants don't seem to run, but that's because "running" is defined in terms of the characteristics of the gait rather than actual speed. Whether they do or not is really just semantics. The point is that they case be impressively fast--faster than most people--whether they're lumbering or running or whatever gait they use.


You've hit on something very important: if you scale up an animal (or anything at all, really), its volume will scale as the cube of the size--and therefore if the basic composition is similar, the weight will be likewise greater. In other words, if you became 10 times larger, you would weigh 10³ = 1000 times more. However, the strength of your bones and muscles depends on their cross-sectional area, so they will only be 10² = 100 times stronger. Effectively, scaling you up 10-fold makes you ten times weaker and frailer in terms of being able to move yourself around.

(Actually, it's worse than that. Your muscles and bones will be ten times weaker relative to your weight, but since this also applies to your heart and blood vessels, your stamina will be around ten times smaller on top of that.)

So, what's that mean? Just that you can't scale something up and expect it to perform. Those giant ants in old horror movies, for example, are completely unphysical--those twig legs would never support their new body weight, for example. Ants can't be size of elephants. But on the other hand, elephants don't have scrawny ant-legs, but massive pillars large enough to handle the stress on them.


The environment was very different back then. There are probably many biological factors contributing to this that I'm not aware of, but a very obvious one that I do know of is the elevated oxygen level in the atmosphere during the Cretaceous period. The tired feeling you get in your muscles is primarily from a buildup of lactic acid that happens when the muscles don't get enough oxygen (and that's also why exertion also makes you breathe faster--to get more oxygen). But if you could intake more oxygen with every breath, then for the same muscle mass, you could support larger wings and be able to beat them faster without tiring as much.

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Alright, first think of this: animals get their material from plants (perhaps indirectly, e.g., though eating other animals, but eventually herbivores come into the food chain, and from there plants). Where do, say, tress and grass get their material from when they grow?

(Actually, this is a very good exercise. Try to be very specific about where you think most of the plant's mass comes from. Many people get this wrong for some reason.)


True, the coal didn't exist, but is that the same thing as saying that the matter than ultimately ended up being coal didn't exist?


Think about where that plant and animal material ultimately comes from.


By all means, but it doesn't seem to me that you're properly accounting for it. You seem to be saying that it just appears from nowhere.

Edit: merged posts.