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  #21  
Old 28th February 2016, 03:35 AM
surreptitious57 surreptitious57 is offline
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Default Re: Accident

Small point of pedantry : galaxies do not sit still while space expands between them. They just move slower
for they have mass. Whereas empty space does not. And in actual fact nothing in the observable universe is
at absolute rest. For every object of mass is affected by the gravitational attraction of other objects of mass
As even light which has zero mass can be bent by gravity around very large objects of mass like black holes
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  #22  
Old 28th February 2016, 03:49 AM
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hackenslash hackenslash is offline
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Default Re: Accident

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surreptitious57 said View Post
Small point of pedantry : galaxies do not sit still while space expands between them. They just move slower for they have mass.
Strictly true, but entirely misleading in the context of this discussion, because we're talking about cosmic expansion, and local motion is entirely irrelevant to that. In that context, galaxies sit still while space expands between them.

If you're going to correct someone, make sure you're talking about the same thing.

Quote:
And in actual fact nothing in the observable universe is at absolute rest.
You might want to check with Herr Doktor Einstein about that, because he asserted that everything in the universe has equal claim to being at rest.

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For every object of mass is affected by the gravitational attraction of other objects of mass
What about an object equidistant between two identical masses? Are you8 sure gravity is relevant here?

Quote:
As even light which has zero mass can be bent by gravity around very large objects of mass like black holes
I know I've told you this before at least once, so it should be sinking in by now; light isn't being bent, it's the space that's being bent. The light is still travelling in straight lines (geodesics).

Seriously, if you're going to correct me, make sure you aren't talking bollocks. Muphry's Law strikes again.
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  #23  
Old 28th February 2016, 04:10 AM
Spearthrower Spearthrower is offline
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Default Re: Accident

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surreptitious57 said View Post
Why is the atmosphere not regarded as the boundary of Earth?
Most importantly, it's not just 'atmosphere' but a certain molecular density, because you'll find plenty of atmospheric molecules outside that boundary.

Also, you could rightly consider the point where Earth's gravitational pull ceases to be felt the boundary of Earth.

Any which way, heat certainly does escape the 'boundary'.

Last edited by Spearthrower; 28th February 2016 at 04:12 AM.
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  #24  
Old 28th February 2016, 04:25 AM
surreptitious57 surreptitious57 is offline
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Default Re: Accident

An object that is equidistant between two identical forces or objects of mass may have other forces or objects acting
upon it too. If they had a greater gravitational attraction then gravity would obviously be relevant in such a scenario
A geodesic is a straight line in space which is bent by gravity. You did indeed correct me about it with regard to light
but that is how I imagine it to be. Though I will try to avoid repeating the error for it is really not that hard to rectify
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