How strong is gravity?

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acecharly

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How strong is gravity?
« on: 12/06/2012 21:36:40 »
We think of gravity as very weak, but when its possible to fit every human person on the planet into a grapefruit if you removed all the space between its nucleus and electrons, maybe it just doesnt have much to work with and is actually incredibly strong.

Any thoughts welcome

Cheers Ace

CliffordK

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Re: How strong is gravity?
« Reply #1 on: 12/06/2012 23:51:42 »
Interesting idea that the density of "normal matter" is in fact relatively low compared to the density of nuclear material.

Obviously chemical and intermolecular bonds hold a person together, and not gravity.  And gravity is much weaker than for example a Carbon-Carbon molecular bond.

In a sense "weight" is arbitrary, and just a measurement of our interactions with Earth's gravity.

Density is irrelevant when considering interactions between cosmic bodies.  The gravitational force between the Earth and moon would be the same if the Earth and moon were 10x as dense, or $$\frac{1}{10}$$ as dense, assuming the same mass.

To us, the average density of planet Earth is more or less a measurement of the distance between us and the center of mass, so in part Earth's density is important.

Soul Surfer

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• keep banging the rocks together
Re: How strong is gravity?
« Reply #2 on: 13/06/2012 00:04:30 »
An interesting and very relevant point acecharly. This space exists because the electrons are fermions and need space because of their uncertainty.  Normal matter as we know it is incredibly dense compared the mean density of matter throughout the universe.  Even at the point where the cosmic microwave background was generated when the universe was around the temperature of the surface of a star it was less dense that the earth's atmosphere is now.  That's a helluva lot more space.

It is very interesting to think what might have created this space.  This is generally called Dark energy.  If there was a very light fermion that interacted only by gravity lets call it a gravitino.  it could well in effect create this space with its large uncertainty volume and gravitational repulsion when the pericles are too close together.
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