What keeps the stars apart?

Okay, so you wouldn't actually "see" the black hole approaching, but that wouldn't change the fact that it was approaching.

 

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the other star is accelerating away from you. and that would be a valid observation. the presence of the black hole invalidates your conclusion.

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I had always wondered if antimatter would be repulsive to matter and vice versa. It is my understanding that when we create antimatter, it is always in amounts too small for gravity to have any noticeable effect on it. Are there any theories on this? Is it possible to design an experiment to detect this? (Is it possible to design an experiment to detect the effects of gravity on an electron?)

 

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A 1999 FAQ .

 

Being an inertial observer doesn't make physics errors valid, and, anyway, you're not an inertial observer, since you're accelerating. Do you know what the word inertial means?

 

"We look at distant glaxies and again there is s certain uniformity.' -
No, pretty much everything you can see with your bare eyes is inside the milky-way.

 

Do you?
In GR a free falling observer is inertial.
A stationary observer in curved spacetime is accelerating (eg/ standing on the earths surface is considered as accelerating, but a mass in free fall is considered inertial)

 

From: http://empl.ksc.nasa.gov/Links/physglossary/physglossary.htm

"inertial reference frames move at constant velocities."


From: http://physics.about.com/cs/generalrelativit1/a/110703_2.htm

"an inertial reference frame is one that is not accelerating"


There is no such thing as a stationary observer. Observers are only stationary compared to something else. That's why they call it Relativity.

 

What keeps the stars apart?

can be rephrased as :What makes it unlikely for stars to attract and collide?

Just remember : r squared

 

Brandon, the free falling observer is accelerating with respect to some frames (in this instance, its the BH) but its rest frame is inertial because if you enter that frame, things follow SR locally.
The observer on the free falling star is considered inertial for this reason- as long as you ignore tidal effects.

 

Antimatter has ordinary mass, and therefore ordinary gravity.

There is an entirely theoretical type of matter, called Negative Matter
which (if it existed) would have negative mass and negative gravity;

this negative gravity is the same as the repulsive force pushing apart the Universe, and really would be repulsive.

Oh and negative matter is supposed to have negative inertia, if you can believe that.

No negative matter has ben observed, nor created, although it would make traversible wormholes a possibility.

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SF worldbuilding at
www.orionsarm.com

 

The universe is expanding, Right?

 

Yes, but the acceleration of that expansion is is caused by a tiny amount of negative energy which is contained within the vacuum of space itself. This thinly spread negative energy is what is generally called dark energy; it is apparently not possible to collect this negative intrinsic energy into a more concentrated form.