Is antimatter invisible?

Question

If not, say there was a pile of it in front of me in space. What would it look like?

Answer 1

Interesting question. Antimatter can be contained only in a complete vacuum. If you had some antimatter that wasn't contained, it would look like a flash of light as it converted to energy.

On the other hand, if you had a container that housed a perfect vacuum holding antimatter, you wouldn't be able to see the anti-matter at all unless the container were transparent - or had a window that would allow viewing (I should note that such a container is not currently technologically feasible).

That leaves the question of what happens when light interacts with anti-matter in a vacuum. That I don't know. My initial guess would be the same as the non anti-matter counterpart, but it might absorb light differently.

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Here is an exerpt from an article I read:

"When antimatter and matter come into contact, they annihilate each other and create two photons: p*(p-) -->two photons. In any reaction between particles, anti or normal, the baryon and lepton numbers must be conserved. In other words, the total baryon and lepton number of the reactants must equal the total baryon and lepton number of the products. There is a problem with the Standard Model, however. If every particle in the universe was changed to an antiparticle, we would expect a universe that would be a mirror image of our own. However, because not all the properties of antiparticles and particles are the same, the new universe would not look like a mirror image of our own. The difference would result from the fact that the rate at which particle reactions take place in our universe would not be equal to the rate in the mirror universe. Rate(X -->B + L-) not equal to Rate(X --> B- + L) "

I'm not sure what is meant by "not all the properties of antiparticles and particles are the same". There is more here:
http://aether.lbl.gov/www/science/antimatter.html

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Here's another reference that has a different claim:
http://www.princeton.edu/~dbaumann/PHY115Questions.pdf#search='antimatter%20color'

I think the second reference makes a valid point about the excited state of matter vs anti-matter. It correctly points out that two atoms, one matter the other its anti-matter counterpart, would emit the same frequency of light if both were excited to the same state (since the reason an object reflects light is due to electrons falling from an excited state back to their base state). The question that comes to my mind though, is would a light source excite both the matter and anti-matter in the same way.

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I think the bottom line is anti-matter wouldn't be invisible, but since the only anti-matter that has been created so far is anti-hydrogen (http://www.aip.org/enews/physnews/2002/split/611-1.html), which is invisible as matter, the question seems to be unresolved.

Answer 2

Since No one has ever made enough to look at its a damn interesting question, Lets assume its in an absolute vacuum so that there is no regular matter near by. If not the answer is simple: It looks like an atomic explosion! Now comes the fun part. We see by interactions of photons on the rods and cones on our retina within our eyes. So the question boils down to: Given an ambient light source how does the antimatter effect the photons? I suspect that the answer is the same as for regular matter, some are reflected some are absorbed some are refracted, some pass straight through, and some are scattered. But the assumes a complex "anti-atomic" structure . The antimatter produced to date has been just elementary particles. The light would mostly pass straight through, and they would be invisible, unless they were unstable and giving off created photons through decay processes.

Answer 3

We haven't yet made enough to be visible; only microscopic amounts. If there were any naturally-occurring antimatter in the solar system, we';d know about it by now, because its signature of hard gamma radiation every time it came into contact with, say, gas molecules, would be hard to mistake for anything else.

If there was a pile in front of you, it would look like a blindingly bright flash of light. It probably does have similar colors to those we know, but I wouldn't want to get that close to it.

Answer 4

One interesting thing about antimatter is that it's exactly the same as regular matter but with reversed electrical carge and their tendency to annihilate one another in blinding flashes of light.

So, if you somehow had a blob of antimatter *completely* isolated from normal matter, it would look totally ordinary! This experiment is, of couse, impossible; that just increases my baseless courage in my analysis however. :-)