Expansion of space and dark matter

In summary: It is false that gravity waves travel at the speed of light.2] Yes, we can interpret the goings on of a black hole beyond a certain extent. For example, if a black hole swallowed a star, the star's light would be bent as it passed by the black hole. This is due to the strong gravitational force exerted by the black hole.
  • #1
spacetime1234
6
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question 1. i need some help understanding this. it is proven that the universe is infinitely expanding correct? what is the exact reason for that?

question 2. i have a couple questions on dark matter. does dark matter give off its own gravity bending space-time, I am assuming ?
 
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  • #2
spacetime1234 said:
question 1. i need some help understanding this. it is proven that the universe is infinitely expanding correct? what is the exact reason for that?

question 2. i have a couple questions on dark matter. does dark matter give off its own gravity bending space-time, I am assuming ?

1. It is believed that the universe is expanding and that it will continue. Is it PROVEN? There IS evidence, which is why we believe this, but to say it is proven is kind of iffy. It's better to say that the current evidence combined with our currrent understanding of physics supports the idea that the universe is expanding. The reason for the expansion is currently unknown. There are several hypothesized things such as dark energy that might explain it, but we currently don't know.

2. From our current theory on dark matter, it DOES interact through gravity. Meaning that it does have gravity like normal matter does. This is supposedly the reason why galaxies are held together, as the amount of matter that is visible to us currently doesn't seem to be enough to hold everything together. That and other discrepencies as well.
 
  • #3
spacetime1234 said:
question 1. i need some help understanding this. it is proven that the universe is infinitely expanding correct? what is the exact reason for that?
By "reason," do you mean what is the evidence, or what is the physical mechanism that people invoke to explain the observations?
 
  • #4
so, a possible theory would be that dark matter gives off a repulsive force that is expanding the universe?
 
  • #5
yes the evidence
 
  • #6
spacetime1234 said:
so, a possible theory would be that dark matter gives off a repulsive force that is expanding the universe?

No, that is Dark Energy. Dark matter interacts through gravity and pulls stuff in like normal matter does.
 
  • #7
spacetime1234 said:
yes the evidence

One of the biggest points in evidence is the increasing amounts of redshift as we look at things further and further away from us.
 
  • #8
very good explanation thank you
 
  • #9
spacetime1234 said:
so, a possible theory would be that dark matter gives off a repulsive force that is expanding the universe?

As Drakkith points out, DM has an attractive force, just like regular matter.

Indeed, DM was initally hypothesized as an explanation of an observed larger gravitational attraction than expected. (i.e. the gravitational effect was observed first and, without any explanation forthcoming, it was thus proposed that there was some extra matter floating about that could not be seen - i.e. dark).
 
  • #10
without dark matter would light still bend in space?
 
  • #11
spacetime1234 said:
without dark matter would light still bend in space?

Yes. Gravity from normal matter bends light. One of the first experiments to prove Einsteins theories on relativity was measuring the bending of light around the sun.
 
  • #12
very well sir. another question for you. If Newtons third law states that every reaction has an equal and opposite reaction , would it be possible for everything a black hole intakes it would spew out somewhere else maybe a white hole ?
 
  • #13
spacetime1234 said:
very well sir. another question for you. If Newtons third law states that every reaction has an equal and opposite reaction , would it be possible for everything a black hole intakes it would spew out somewhere else maybe a white hole ?

1] That is a misapplication of Newton's Law.

2] We know that the infalling matter of a black hole does not go anywhere. We know this because we can measure the BH's gravity, which is in direct correlation with the amount of matter there.
 
  • #14
Drakkith said:
One of the biggest points in evidence is the increasing amounts of redshift as we look at things further and further away from us.

There is also a second, independent source of information from the CMB anisotropy, and it confirms the nonzero cosmological constant.
 
  • #15
Firstly let it be known that I am a total philistine. I dropped out of community college before I even got an AA so don't let my ignorance offend you who is reading this.

In response to the certainty that the matter in black holes does not go anywhere -- Ok, so from my limited understanding according to Einstein, gravity waves travel along the fabric of spacetime at the speed of light i.e. the sun disappears, it would take approx 8 minutes (or what have you) for the gravitational effects to be felt. Does a black hole warp spacetime to an infinite degree? Are we necessarily able to interpret the goings on of a black hole beyond a certain extent in that warping? In my mind I'm seeing that when spacetime is warped/stretched it takes longer for the gravitational wave to travel along it to an outside point and be "observed" It almost sounds like I'm asking whether or not gravity affects itself which sounds bizarre to me now that I think about it.

That aside, I found this thread on google because I was searching for information on dark matter. I had the thought "What if mass isn't what warps spacetime, but an already warped spacetime is what attracts/pools mass?" I made the assumption that if this were the case there would be places where spacetime was warped but there would be no observable mass because there simply wasn't any nearby matter to "pool" into the warp in spacetime, so I started looking into dark matter.

Once again, I apologize for my ignorance. I'm simply an unemployed drunkard with a computer.
 
  • #16
Theget welcome to the forum. I think it is good that you and others ask questions. Perhaps the various threads already here may help?
 
  • #17
Sorry, I should've looked through the forum before replying.
 
  • #18
spacetime1234 said:
question 1. i need some help understanding this. it is proven that the universe is infinitely expanding correct? what is the exact reason for that?

question 2. i have a couple questions on dark matter. does dark matter give off its own gravity bending space-time, I am assuming ?

There is none proof of 1. What exists are observations that is currently expanding.

I think that you confound dark matter with dark energy
 

1. What is the expansion of space?

The expansion of space refers to the theory that the universe is constantly expanding and the distance between galaxies and other celestial objects is increasing over time. This expansion is believed to have started with the Big Bang and is still ongoing.

2. How does dark matter play a role in the expansion of space?

Dark matter is a type of matter that does not interact with light or other forms of electromagnetic radiation, making it invisible to telescopes. It is believed to make up about 85% of the total matter in the universe and its gravitational pull is thought to be responsible for the acceleration of the expansion of space.

3. What evidence supports the existence of dark matter?

There are several lines of evidence that support the existence of dark matter. One is the observation of the rotation of galaxies, which suggests the presence of more mass than what can be accounted for by visible matter. Another is the gravitational lensing effect, where the gravity of dark matter bends the path of light from distant objects. Additionally, observations of the cosmic microwave background radiation also support the existence of dark matter.

4. How does the expansion of space affect the formation of galaxies?

The expansion of space plays a crucial role in the formation of galaxies. As the universe expands, it causes the matter to spread out, creating regions of lower density. These regions then become the sites for the formation of galaxies, as the matter is pulled together by the force of gravity. Without the expansion of space, it is unlikely that galaxies would have formed.

5. Is the expansion of space accelerating or slowing down?

Current evidence suggests that the expansion of space is accelerating. This was first discovered through observations of distant supernovae in the late 1990s. This acceleration is thought to be driven by dark energy, a mysterious force that counteracts the pull of gravity and causes the expansion of space to speed up.

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