Expanding Universe: What We See & How We Know

[Swimfit]

Thank you for taking all the time helping me too understand about the expansion. I was watching some videos on YouTube about the expansion of the universe. It was very interesting. It was saying that the outer most stars that are in the red shift that space around them could reach faster than the speed of light, and that they could soon get past the point of us being able to see them anymore. Are they too reach those speeds because of less gravity? Swimfit

 

[phinds]

Thank you for taking all the time helping me too understand about the expansion. I was watching some videos on YouTube about the expansion of the universe. It was very interesting. It was saying that the outer most stars that are in the red shift that space around them could reach faster than the speed of light, and that they could soon get past the point of us being able to see them anymore. Are they too reach those speeds because of less gravity? Swimfit

The "outermost stars" in the OBSERVABLE UNIVERSE are moving away from us at 3 times the speed of light because of the not-understood phenomonon we call "dark energy", which seems to be the same thing as the "cosmological constant" which causes the DIMENTIONS between not-gravitationally-bound systems to increase, and to increase more the farther apart they are.

 

[Swimfit]

After I sent that last message the thought came to me dark energy. It's funny I always thought that nothing could travel faster than the speed of light. But that rule pertains to massive objects and space has no mass, so can go as fast it wants. Now does dark matter have mass? Or is that an unknown, or unmeasurable? God all this stuff fascinates me. Swimfit

 

[alexg]

After I sent that last message the thought came to me dark energy. It's funny I always thought that nothing could travel faster than the speed of light. But that rule pertains to massive objects and space has no mass, so can go as fast it wants. Now does dark matter have mass? Or is that an unknown, or unmeasurable? God all this stuff fascinates me. Swimfit

Since dark matter is known exclusively through it's gravitational effects, and since gravitation implies the existence of mass, I'd guess that it does indeed have mass. But if it's a kind of mass which does not interact electromagnetically with ordinary mass, we'd have no way of detecting it other than gravitational effects.