Am 18.10.2015 um 08:03 schrieb Stephen:
> On 10/18/2015 3:44 AM, clipka wrote:
>> Einstein's General Theory of Relativity is nearly a hundred years old by
>> now, but I think it is only now, in the age of YouTube, that a
>> fundamental understanding starts seeping into common knowledge of what
>> the theory /really/ means.
>>
>> For instance, according to the General Theory of Relativity,
>> gravitational pull is caused by the curvature of spacetime. That's what
>> it says, isn't it? Right?
>>
>> Err... nope.
>>
>> What the General Theory of Relativity /really/ says is that there is /no
>> such thing/ as gravitational pull. To the contrary: What really makes
>> you stick to the ground is not a force pushing /you/ /down/, but a force
>> pushing /the ground/ /up/. More specifically, the electromagnetic forces
>> between the atoms of the earth push it apart with such a force that the
>> ground races upward at an acceleration of 9.81 m/s^2 - and all the while
>> the fabric of space near and at earth just contracts at an equivalent
>> rate, shriveling like the surface of a punctured balloon, so that the
>> effective distance between the atoms never gets any bigger despite their
>> accelerated motion through space.
>>
>> I had been pondering this for a few days now, when I stumbled across
>> this video which I think gets the idea across quite well:
>>
>> https://youtu.be/NblR01hHK6U
>>
> 
> 
> So we should think that instead of the Earth attracting the apple with a
> force of, say, 1.0 N. The apple attracts the Earth with a force of
> 5.86E+25 N. Makes sense.

No, no - not at all.

What happens is that Earth, by virtue of having mass, gobbles up space
inside and around it. Always. Constantly. Whether there are any apples
out there or not. (So does the apple, but that's negligible compared to
Earth's dietary budget.) There's no acceleration or even movement
involved there /per se/ - in the vicinity of matter, distances just
shrink over time. Fast.

If it was only for this mechanism, earth would shrivel to nothingness in
a matter of... minutes? hours? Dunno, but certainly in less than a day.
Space between the elementary particles would just shrink to zero.

Fortunately, electromagnetic force comes to our rescue: The electron
clouds of any two atoms in the universe repel each other. Partially this
is compensated by the fact that the electron clouds of any atom  in the
universe also attracts the nucleus of any other atom, but on average the
net EM force is repelling. And there are a lot of atoms in the Earth. So
the atoms making up earth constantly accelerate away from each other.
Earth is exploding.

Now while this seems even more bad news, it is important to note that
the repelling EM force heavily depends on the distance between the
atoms, much more so than the space-gobbling mechanism does. So while
space is busy shriveling away and Earth is busy exploding within this
space, these two mechanisms have long reached an equilibrium: The
distance between Earth's center and its surface is constant (save for
some other minor effects, such as Earth accreting more solid material
and evaporating light gases such as Helium).

But even though Earth's radius is constant, Earth's surface still /does/
accelerate upward. Not because it is attracted by apples out there, mind
you - to the contrary: Earth and the dropping apple /repel/ each other.
A tiny bit. But much more so, Earth is repelling itself, and hurtles
onward towards the unsuspecting dropping apple - until the two come so
close that EM forces between Earth and the apple suddenly skyrocket, and
(after a bit of bouncing around) come into equlibrium with the collapse
of space. The apple now races outwards along with Earth's surface.

Whoosh.

We're riding an explosion that is the only thing standing between us and
the formation of a black hole.


Also, think of this: If you throw an apple, it moves through space in a
/straight/ line - any apparent curvature of its trajectory is due to
Earth's surface constantly accelerating upwards. Not towards the apple
but away from Earth's center. In a lump of space that's busy shrinking.

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