[QUOTE=Strain of Thought]
About the expansion of stars:
They do not start as extremely dense matter and then grow to form planets, they start as faint clouds the size of solar systems, made mostly of hydrogen, the smallest atoms possible, and then shrink. The planets are the little bits that don’t get sucked into the forming star.
A star continues to lose mass over its entire lifetime, both in the form of direct conversion to energy through fusion and gas escaping as solar wind. Many stars do expand tremendously near the end of their lifetime, but they are not gaining mass when they do so. To apply a simile, they are puffing up like marshmallows in a microwave, because they are then fully cooked. So this expansion comes at the cost of an equal amount of density.
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What you’re saying is exactly what I meant. I don’t mean how stars are formed, I’m talking about once they are formed. They do expand, once they are a star. And what I was asking is why is it so preposterous to think that a planet may expand without losing significant mass, by decreasing it’s density?
If the molten core is expanding, then the original “surface” would indeed crack apart exposing the new surface of cooling molten core. Which is the theory that I’m questioning here. Why couldn’t the earth expand by losing density, muchlike a star?
Forgive my persistence here. But I am exercising a sort of reverse skepticism here. I’m interested in the science that proves the theory of an expanding earth wrong. So far the best “hard” argument I’ve heard is the exponential change in gravity being undetected in fossil records. I can’t say I really fully or even partially grasp the idea of the curvature of space.
Also, if the earth were expanding at the rate of increasing it’s radius by half every 2 billion years. Would we be able to detect such growth at this time?
[QUOTE=Chronos]
The Earth’s crust is accelerating outwards, but that doesn’t mean it’s expanding. When you can understand how those two statements can be simultaneously true, Grasshopper, you will understand the curvature of space.
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Negative acceleration?
Ludovic, that depends on your convention for the direction of acceleration. If you call the outward direction positive, then the acceleration of the Earth’s surface is positive. But that doesn’t really help the conundrum, either way.
[QUOTE=Chronos]
The Earth’s crust is accelerating outwards, but that doesn’t mean it’s expanding. When you can understand how those two statements can be simultaneously true, Grasshopper, you will understand the curvature of space.
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Wait, I thought the Earth’s crust is constantly accelerating inwards (except the poles), but not getting any smaller. And that when Grasshopper understood that, they would understand the vector nature of acceleration.
Man, I don’t know about physics. Maybe it would be less confusing to be a Zen monk..
In Newtonian physics, that’s true. But my statement was from relativity. In General Relativity, gravity is considered to be a “fictitious” force, just like the centrifugal force or the Coriolis force, so something which is sitting on the surface of the Earth is accelerating.
