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AaronKnight
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Is it possible that a far off galaxies that we are unable to reach are made up of anti-matter? How do we know that they are made up of matter?
We're pretty darned sure this can't be the case. As mathman noted, if this were the case we would see a lot of matter/anti-matter annihilations. We have looked for these, by the way, and don't see them.AaronKnight said:Is it possible that a far off galaxies that we are unable to reach are made up of anti-matter? How do we know that they are made up of matter?
Vanadium 50 said:The lack of annihilation radiation, like mathman points out, provides a powerful constraint. Any antigalaxies must be very far away indeed. However, eventually the annihilation radiation is washed out in the diffuse x-ray background, so there is a limit to this technique. A better method is to launch a particle detector into space and look for anti-helium and anti-iron nuclei in cosmic rays produced in distant anti-galaxies. Only test runs have been made so far, but when the whole experiment is run, the limit will be pushed close to the edge of the visible universe.
Chalnoth said:We're pretty darned sure this can't be the case. As mathman noted, if this were the case we would see a lot of matter/anti-matter annihilations. We have looked for these, by the way, and don't see them.
Well, it's not a cloud of anti-matter. It's a cloud where matter-antimatter annihilation is occurring. Though apparently its direct causes aren't well understood, this doesn't surprise me a whole lot because there are a lot of extremely energetic interactions going on in and near the galactic core. One possible explanation might be that it's just a cloud of normal matter caught in a jet of almost equal parts matter and anti-matter.twofish-quant said:Just to clarify, we don't see matter/anti-matter radiation from distant galaxies. There is however a rather large cloud of anti-matter in the center of the milky way
http://apod.nasa.gov/apod/ap970501.html
Well, no, not really. It just comes back to the CMB: our early universe was extremely uniform, so that there really wasn't any place for the anti-matter to avoid annihilation early-on. This would have been the same for every place in the universe that stemmed from our inflation event.AaronKnight said:Due to the universe being 13.7 billion years old means that we can only see light that has taken that long to reach us. Could matter-antimatter annihilations occur further away than that so the gamma radiation hasnt reach us yet to detect?
how are we so sure there's no bumpy spots i mean sure our area is pretty calm but if this were the ocean we were talking about you wouldn't see a glassy calm spot and think the whole ocean were glassy calm the universe is 156billion lightyears across http://www.msnbc.msn.com/id/5051818/ and is 15 billion years old assuming we can see 15 billion lightyears in both directions this leaves 126billion lightyears of stuff we cannot see.. so whose to say matter isn't the rare item in another 30 billion lightyear swath of the cosmos i know it says that we can see those objects due to expansion but we only have a really young snapshot of the other side of the universe no idea what it looks like now and definantly no radiation can get here from there anytime soon (soon being the next 100billion years)Well, no, not really. It just comes back to the CMB: our early universe was extremely uniform, so that there really wasn't any place for the anti-matter to avoid annihilation early-on. This would have been the same for every place in the universe that stemmed from our inflation event.
Er, the 156 billion light years is what we can see. The curvature of space-time allows us to see further than you might otherwise expect from naively looking at the age of our universe.VooDooX said:how are we so sure there's no bumpy spots i mean sure our area is pretty calm but if this were the ocean we were talking about you wouldn't see a glassy calm spot and think the whole ocean were glassy calm the universe is 156billion lightyears across http://www.msnbc.msn.com/id/5051818/ and is 15 billion years old assuming we can see 15 billion lightyears in both directions this leaves 126billion lightyears of stuff we cannot see.. so whose to say matter isn't the rare item in another 30 billion lightyear swath of the cosmos i know it says that we can see those objects due to expansion but we only have a really young snapshot of the other side of the universe no idea what it looks like now and definantly no radiation can get here from there anytime soon (soon being the next 100billion years)
That's being misreported in the article.Er, the 156 billion light years is what we can see.
Sorry, yeah, silly mistake on my part.Ich said:That's being misreported in the article.
The radius of the observable universe, as defined in the article, is about 46.5 Gly, not 78 Gly.
Cornish et al. actually reported a minimum diameter (minimum translational distance) of the whole universe of 78 Gly.
There are some more glitches in those articles, obviously the press release was not really well formulated.
Matter is any substance that has mass and takes up space, while anti-matter is the opposite of matter and has the same mass but opposite charges. When matter and anti-matter come into contact, they annihilate each other, releasing a large amount of energy.
Studying matter and anti-matter in distant galaxies can help us understand the origins of our universe and the fundamental laws of physics. It can also provide insights into the behavior and interactions of these particles in extreme environments.
Scientists use a variety of instruments, such as telescopes and particle detectors, to study the light and energy emitted from distant galaxies. They also look for specific signatures and patterns in the data that can indicate the presence of matter and anti-matter particles.
Studying matter and anti-matter in distant galaxies can have practical applications in fields such as energy production and medical imaging. By understanding how matter and anti-matter interact, we can potentially harness their energy for efficient energy production. Additionally, studying anti-matter can also improve our understanding of how it can be used in medical imaging techniques.
One theory suggests that the universe began with an equal amount of matter and anti-matter, but due to some unknown asymmetry, more matter was created, leaving behind the matter we see today. Another hypothesis is that there are parallel universes where anti-matter dominates, explaining why we see a lack of it in our own universe. Ongoing research and experiments aim to provide more evidence and insights into these theories.