PDA

View Full Version : Dark matter/energy?



Cael0
2012-Sep-28, 07:40 PM
As our knowledge of this mysterious substance increases, we learn that dark matter/energy counteracts the force of gravity and pushes matter apart. Could this mean that dark matter is comprised of something similar to an anti-graviton? Though gravitons are electrically neutral and therefore shouldn't have a respective anti-particle, perhaps gravity itself could be a charge of matter, where gravitons give matter positive gravity, and anti-gravitons (dark matter) gives matter negative gravity.

As a side thought: It is known that gravity causes a bend in space-time, so maybe it bends space-time in a certain direction. Instead of this (http://illustration.pixmac.com/4/space-time-and-gravity-space-pixmac-illustration-44560807.jpg) happening, anti-gravity bends space-time in the opposite direction, causing matter to "roll" away from the bend, instead of "rolling" into it.

ShinAce
2012-Sep-28, 09:18 PM
Remember that dark matter causes gravity.
Dark energy seems to not care for gravity and does its own thing.

If you're trying to propose an anti-gravity, you still have an immediate problem with dark matter. Dark matter = gravity; not anti-gravity.

Cael0
2012-Sep-28, 09:41 PM
I thought it was the graviton that "causes" gravity. Ah well, perhaps I'm mistaken. Back to wikipedia!

Swift
2012-Sep-28, 09:48 PM
Remember that dark matter causes gravity.
Are you sure about that? Dark matter responds to gravity (it appears gravity is the only force it does respond to), but I never heard it causes it.

Van Rijn
2012-Sep-28, 09:57 PM
Well, mass/energy will "cause" gravity - baryonic matter, cold dark matter, even photons.

Dark matter was introduced in the first place because of galaxy rotation curves that weren't dropping off as expected, indicating there was much more mass (with the associated gravitational effects) than could easily be detected.

ShinAce
2012-Sep-28, 10:10 PM
Are you sure about that? Dark matter responds to gravity (it appears gravity is the only force it does respond to), but I never heard it causes it.

I'm not saying it's the root cause of all gravity. Beyond that, Van Rijn has explained it well so I won't repeat.

I'm saying it does not have an anti-gravity to it.

Noclevername
2012-Sep-29, 12:56 AM
As our knowledge of this mysterious substance increases, we learn that dark matter/energy counteracts the force of gravity and pushes matter apart. Could this mean that dark matter is comprised of something similar to an anti-graviton? Though gravitons are electrically neutral and therefore shouldn't have a respective anti-particle, perhaps gravity itself could be a charge of matter, where gravitons give matter positive gravity, and anti-gravitons (dark matter) gives matter negative gravity.

As a side thought: It is known that gravity causes a bend in space-time, so maybe it bends space-time in a certain direction. Instead of this (http://illustration.pixmac.com/4/space-time-and-gravity-space-pixmac-illustration-44560807.jpg) happening, anti-gravity bends space-time in the opposite direction, causing matter to "roll" away from the bend, instead of "rolling" into it.

You are mixing up two unrelated concepts. The only thing dark matter and dark energy have in common is the word "dark" in the names.

Xibalba
2012-Sep-29, 03:43 AM
Could it be that the "hot gas cloud" recently discovered around the Milky Way renders useless the presence of dark energy/matter? DM was thought to compensate the lack of matter in galaxies, that would not be able to maintain themselves as they were if it weren't for this theoretical invention.

Maybe that cloud of hot gas will erase the need of dark energy and/or matter?

Cael0
2012-Sep-29, 03:48 AM
Could it be that the "hot gas cloud" recently discovered around the Milky Way renders useless the presence of dark energy/matter? DM was thought to compensate the lack of matter in galaxies, that would not be able to maintain themselves as they were if it weren't for this theoretical invention.

Maybe that cloud of hot gas will erase the need of dark energy and/or matter?

Another thought I had, as I believe the article I read stated that the gas cloud containt the mass of several galaxies, and dwarfs the Milky Way by comparison.

antoniseb
2012-Sep-29, 03:57 AM
... Maybe that cloud of hot gas will erase the need of dark energy and/or matter?
The article said it could account for the "missing baryon" problem, which is that about half to three quarters of the normal matter we expect hasn't been found (perhaps until now), but that is still only about 15% of the missing mass, the rest of which is presumed to be dark matter.

Noclevername
2012-Sep-29, 04:03 AM
Could it be that the "hot gas cloud" recently discovered around the Milky Way renders useless the presence of dark energy/matter? DM was thought to compensate the lack of matter in galaxies, that would not be able to maintain themselves as they were if it weren't for this theoretical invention.

Maybe that cloud of hot gas will erase the need of dark energy and/or matter?

Dark energy is our placeholder name for the force that seems to be accelerating universal expansion, and is not related to dark matter, the mass that surrounds galaxies and interacts with gravity but does not show up via electromagnetism.

IIRC, the gas cloud doesn't have nearly enough mass to account for observations.

icarus2
2012-Sep-29, 12:25 PM
As our knowledge of this mysterious substance increases, we learn that dark matter/energy counteracts the force of gravity and pushes matter apart. Could this mean that dark matter is comprised of something similar to an anti-graviton? Though gravitons are electrically neutral and therefore shouldn't have a respective anti-particle, perhaps gravity itself could be a charge of matter, where gravitons give matter positive gravity, and anti-gravitons (dark matter) gives matter negative gravity.

Dear Cael0

I have a similar idea. But this model is non-mainstream model.
It is a personal hypothesis. Therefore, carefully read it.

At the present, it is understood that dark matter and dark energy are completely different in nature. Dark matter corresponds to an attractive gravitational effect, whereas dark energy corresponds to a repulsive gravitational effect. Therefore, dark matter and dark energy have a completely different significance.

But, if negative mass(energy) exists, it is possible to explain the dark matter and the dark energy at the same time.


icarus2 it is not allowed to post ATM in Q&A, don't do it again.
Links removed.

Cougar
2012-Sep-29, 01:10 PM
Could it be that the "hot gas cloud" recently discovered around the Milky Way renders useless the presence of dark energy/matter?

No. From the way the stars and known gas within the galaxy orbit, there must be dark matter inside the galactic disk, not outside.

Dark energy, as others have said, is entirely different. It appears to be a quality of space, not matter.

Cael0
2012-Sep-29, 03:20 PM
Dark matter corresponds to an attractive gravitational effect, whereas dark energy corresponds to a repulsive gravitational effect.

Ok, so maybe mass bends space-time one way, and Dark Energy bends it the other way, and pushes things apart? From my understanding (little as it is), without the presence of a repulsive force, galaxies would be consumed by the supermassive black holes at their centers.

And maybe I simply have no idea what I'm talking about. TT^TT

antoniseb
2012-Sep-29, 05:07 PM
... From my understanding (little as it is), without the presence of a repulsive force, galaxies would be consumed by the supermassive black holes at their centers. ... And maybe I simply have no idea what I'm talking about. TT^TT

All that is required to keep matter from being consumed by a black hole is angular momentum. This is the same thing that keeps the planets and asteroids from being consumed by the Sun. Dark Energy is NOT needed and does not substantially contribute to keeping galactic contents from collapsing into the central black holes.

Cael0
2012-Sep-29, 08:03 PM
All that is required to keep matter from being consumed by a black hole is angular momentum. This is the same thing that keeps the planets and asteroids from being consumed by the Sun. Dark Energy is NOT needed and does not substantially contribute to keeping galactic contents from collapsing into the central black holes.

Ok, so the only correct thing I said was the latter. Thanks for clearing that up for me!

antoniseb
2012-Sep-29, 09:14 PM
Ok, so the only correct thing I said was the latter. ...
You are probably here to learn and exchange ideas. No problem with starting off in the dark.