It’s a simplistic notion, I know. But then I’m kinda simple myself.
The strength of gravity from an object such as a planet depends on (a) the mass of the planet and (b) how far you are from the centre of the planet. For the Earth’s gravity to have been weaker than it is now, the Earth would have had to contain less mass, or have a larger radius. As far as we know, it’s always been the same size and mass.
One theory about the size of the giant sauropods (the big long-necked types like brachiosaurs) is that they may have spent part of their lives in swamps or lakes, so the water would help support their body weight.
If the earth spun faster, would the centripetal force make an appreciable impact on the gravitational pull at the surface?
No. An equivalent centripetal force would have acted on the tectonic plates below the creatures, making the relevant calculations the same as they are for us today.
It would have to spin a lot faster, but yeah. (Duh. I’m supposed to be studying classical mechanics, and I forgot about that one.) Not sure how much faster (anyone feel like doing the calculation?), but something would have to have happened to slow it down. (There’s no ‘drag’ force that could account for the Earth’s rotation slowing.)
I was thinking that the earth’s circumference would increase out from the center, and thereby reduce the force acting on the critters.
I thought the rotation of the Earth was slowing.
We did this calculation in first year physics class… how fast would the Earth have to spin in order for a person to fly off the surface? There was an answer, but it was ridiculously fast.
Pepsi: my point was that I don’t think it could have been going that much faster.
The Earth is slowing because of tidal friction with the Moon. As I understand it, in the time of the dinosaurs the day was about 21 hours. It doesn’t matter exactly what the number is, because the corresponding acceleration is not a signficant part of the gravitational pull - something like 0.45%.
What is making the Earth rotate slower.
‘First Year’ suggests that you were regarding the earth as a solid sphere, not a small solid sphere surrounded by molten rock surrounded by floating solid rock
Achernar: thanks, that’s what I was after. All the physics has fallen out of my head tonight. And I hate not being able to delete the messages where I said something stupid. :rolleyes:
I guess this notion isn’t new, as a quick google led me to a page that pushes this idea.
http://www.kitombo.com/e/gon/0423.html
Has some calculations that I didn’t try to verify.
The short answer to the OP is “No.”
The longer answer involves population dynamics, energy resource utilization, the differences between reptilian-style dentition and mammalian-type teeth, the square-cube law as applied to bare skinned endotherms, Ted Holden, flying feral chickens, physics equations, and some snickering.
A theory that has been discredited for some time, I might add. The skeletal structure of large sauropods is such that they are light but strong. Simple engineering principles are sufficient to explain how they were able to function, without the need for swamps, weaker gravity, alien anti-gravity rays, or anything else.
Oh yeah? Every time we go to the moon, we bring rocks back!
Well, the Earth did have less mass before the addition of the mass of the meteor that killed off all the dinosaurs.
Peace.
I’ve heard that the size of dinosaurs could be contributed to the fact the Earth used to have much more oxygen. More oxygen = larger life forms.
It can be attributed to a lot more plant life. It’s just a theory, but it does make some sense.
If the earth had a larger radius, it is highly unlikely that it would have had the same mass. It is more likely that it would have had a larger mass with the larger radius, thus leading to a more powerful force of gravity.