Your take on Antimatter and Our Universe?

[Abhi_KS]

Okay,

There is a speculation that most of our universe is Antimatter, but, I have a question here : When we see universe, we see stars, nebulae and all the stuff - are they not matter? If yes, then why there are some overwhelming speculations about the constituting percentage of antimatter in our universe? If no? then please explain me how?

[swansont]

Whose speculation would this be? One of the unanswered questions in science is why we have more matter than antimatter.

 

http://en.wikipedia.org/wiki/Baryon_asymmetry

[Sensei]

Okay,

There is a speculation that most of our universe is Antimatter,

 

When you're mixing antimatter with dark matter, that doesn't bode well for future..

[Kramer]

May be the idea of " the universe invaded with anti matter is based in assumption that anti matter has gravity repellent ability toward matter .
If this assumption will be not true, idea fall out.

[Airbrush]

Okay,

There is a speculation that most of our universe is Antimatter, but, I have a question here : When we see universe, we see stars, nebulae and all the stuff - are they not matter? If yes, then why there are some overwhelming speculations about the constituting percentage of antimatter in our universe? If no? then please explain me how?

You are mistaking "dark matter" with anti-matter. They are completely different things.

[Airbrush]

Maybe the OP intended to ask something about this. This comes from the post by Swansont:

 

"Another possible explanation of the apparent baryon asymmetry is that there are regions of the universe in which matter is dominant, and other regions of the universe in which antimatter is dominant, and these are widely separated. The problem therefore becomes a matter/antimatter separation problem, rather than a creation imbalance problem. Antimatter atoms would appear from a distance indistinguishable from matter atoms, as both matter and antimatter atoms would produce light (photons) in the same way. Only in the border between a matter dominated region and an antimatter dominated region would the antimatter's presence be detectable, as only there would matter/antimatter annihilation (and the subsequent production of gamma radiation) occur. How easy such a boundary would be to detect would depend on its distance and what the density of matter and antimatter is along it. Presumably such a boundary would lie (almost by necessity) in deep intergalactic space, and the density of matter in intergalactic space is reasonably well established at about one atom per cubic metre.[3][4] Assuming this is the typical density of both matter and antimatter near a boundary, the gamma ray luminosity of the boundary interaction zone is easily calculated. Approximately 30 years of scientific research have placed boundaries on how far away, at a minimum, any such boundary interaction zone would have to be, as no such zones have been detected. Hence, it is now considered very unlikely that any region within the observable universe is dominated by antimatter.[5]"

 

http://en.wikipedia.org/wiki/Baryon_asymmetry

[swansont]

The idea that there might be antimatter regions is called unlikely. Hence the inquiry as to who was speculating this.

[ScienceLord]

Matter and Anti-Matter cannot theoretically speaking be in different parts of the universe. For example, if Matter was on the side we were in, and Anti-Matter on the other, most of the universe will explode in pure energy. Discussing where you find Anti-Matter is one of the hardest topics.

 

~ Science Lord

[BearOfNH]

[...] For example, if Matter was on the side we were in, and Anti-Matter on the other, most of the universe will explode in pure energy.[...]

 

... so said explosion would constitute a really big bang, then?

[ScienceLord]

Yes, a big bang? If anything a lot larger than that!

 

~ Science Lord

[Strange]

Matter and Anti-Matter cannot theoretically speaking be in different parts of the universe. For example, if Matter was on the side we were in, and Anti-Matter on the other, most of the universe will explode in pure energy.

 

Not necessarily true. Imagine there is a distant galaxy (or galaxy cluster) made entirely of antimatter. There is no matter there for it to annihilate with. Similarly, there is still no antimatter for our local matter to annihilate with.

 

Somewhere, though, there will be a point where the intergalactic gas around the antimatter galaxies (which will itself be antimatter) will meet the intergalactic gas around the matter galaxies (which will itself be matter). That means there will be an area where two very thin (near perfect vacuum) clouds of gas meet. There will be occasional meetings of matter and antimatter, which will annihilate, producing gamma rays.

 

There have been attempts to identify the signatures of such antimatter clouds. So far nothing has been found.

 

(Apart, possibly, from this: http://www.dailygalaxy.com/my_weblog/2013/03/in-2011-an-analysis-of-data-from-a-nasa-fermi-gamma-ray-space-telescope-turned-up-massive-previously-unseen-galactic-struct.html)

[swansont]

 

Not necessarily true. Imagine there is a distant galaxy (or galaxy cluster) made entirely of antimatter. There is no matter there for it to annihilate with. Similarly, there is still no antimatter for our local matter to annihilate with.

 

 

That would not have been true for all time, though. At some point, a relatively high density of matter and antimatter had to be in close proximity, giving a non-thermal radiation signal as they annihilated. We should be able to see the remnant of that signal, if such a scenario were true.

[Strange]

Good point.

[Jdaniel343]

We wouldn't be able to see a galaxy of anti-matter would we, due to the fact that the photons would be anti-matter coming from that galaxy.

[Strange]

We wouldn't be able to see a galaxy of anti-matter would we, due to the fact that the photons would be anti-matter coming from that galaxy.

 

There is no such thing as an anti-photon (or, to put it another way, the photon is its own antiparticle).

 

Photons interact with antimatter in exactly the same way as matter:

http://alpha.web.cern.ch/microwaveInteractionsResult

[Jdaniel343]

Thanks