With the recent newsthat scientists have captured an atom of anti-hydrogen, I was wondering, suppose we develop the capability to create antimatter in large quantities, and capture it for significant periods of time. What would it look like?
In the movies it’s always portrayed as this ethereal, glowing stuff which has whatever physical properties are required to move the plot forward.
But would, say, a block of anti-lead look that different from a block of lead?
It’s been awhile since I’ve taken any Physics, but my understanding is that antimatter has exactly the same physical, optical, and chemical properties as matter. So, a block of anti lead – assuming you could keep it suspended in a vacuum and not let any matter come near it – would look just like lead. Indeed, there is no way to prove that the distant galaxies are composed of matter and not antimatter.
That said, you need keep antimatter away from all matter. The easiest way to do this is to arrange for your antimatter to be a charged gas, a plasma, and use electric and/or magnetic fields to contain and confine it. So, glowing, ethereal antimatter is actually fairly reasonable.
I’m not a physicist, but this website says it would look and sound the same.
Interesting. Thanks.
Although the reasoning about the block of lead (or whatever) sounds right to me, I was under the impression that it is known that distant galaxies are composed of matter and not antimatter. I am pretty sure that I have read that it is (or once was) a challenge to physics/cosmology to explain why matter is so much more common than antimatter in the universe, since, prima facie, they ought to have been created in equal quantities at the big bang.
Am I remembering this wrong? Is there no such problem? If I have remembered right, and we do know that distant galaxies are not antimatter, then, given the points made by the posters above, how do we know that? (And has the problem of explaining why the universe contains so much less antimatter than matter been solved?)
It’s not that the galaxies would look different, it’s that there’s (very tenuous) gas between galaxies. If some of the galaxies were antimatter, there would be reactions between the intergalactic gas and anti-matter gas were they came in contact, and that would be detectable.
From what I understand, the reason scientists don’t believe other observed galaxies are made of antimatter is this. The space between galaxies is not empty, and if a neighboring galaxy was made of antimatter, regular matter would inevitably collide with it creating a detectable amount of radiation. Of course I’m not a physicist, so someone else feel free to contradict me if you’ve got a good argument.
edit
Looks like I was beaten to the punch while I was editing my initial post
Indeed, an appropriately isolated block of anti-lead would look just like a block of lead.
You are remembering right. There are two main ways you can look for distant anti-matter.
(1) We live in a region of matter. If there is a region of antimatter somewhere, the boundary between the matter and antimatter regions would glow with the products of annihilation. No such glow is seen anywhere, and from this non-observation one can set limits on the amount of antimatter, its proximity, and/or its spatial distribution.
(2) If there is an antimatter galaxy out there, it should have (among other things) antimatter stars making antihelium and antimatter supernova spewing antimatter everywhere. No such antimatter component of heavy cosmic rays has been seen.
Coincidentally, the Alpha Magnetic Spectrometer discussed in this thread is aiming to improve the limits on antihelium rates by three orders of magnitude, which (under some not too unreasonable assumptions) would push the limit for antimatter galaxies out to the boundary of the observable universe.
It’s worth pointing out that one of the long-term goals of trapping antimatter, as the ALPHA collaboration has now done, is to study exactly the question posed in the OP. Everything we know so far tells us that antihydrogen should have the same atomic spectrum as hydrogen, but no one has yet performed the spectroscopic measurements because no one has had any trapped antihydrogen to work with.
My physics teacher in high school said something that always bugged me about antimatter. He said that it had negative mass, that if you could somehow put it on a scale with an equal amount of mass, the scale would read 0. This totally blew my mind. Was he fulla crap?
Yes.
That would be negative matter, not antimatter - and just to muddy the waters further, if tachyons exist, they have neither positive nor negative but *imaginary *mass…
Huh.
When I look back on all the crap I learned in high school…
The only justification for showing antimatter as ethereal or glowing is that it would be very hard to perfectly isolate from ordinary mass. (For example, a perfect vacuum isn’t possible). Even a small number of collisions between antimatter and regular matter would produce energy, some of which could escape as visible light.
But I almost hate trying to justify Hollywood at all.
It may not have negative mass, but it may have negative weight. That is, antimatter might fall up instead of down. See for example the New Scientist article “Does antimatter fall up?” or the Slashdot article “Does antimattter fall up or down?”.
What about the explanation that Ex Chemist offered - that the easiest way to store antimatter would be to turn it into plasma?
A small correction, the current accepted scientific view is not that matter and antimatter are identical mirror images of each other, “that antimatter has exactly the same physical, optical, and chemical properties as matter”, but that there are very particular ways in which they differ, the CP violation. These differences in what we have observed between the behavior of matter and antimatter are hugely important as they are presumed to explain why we see little antimatter compared to antimatter in out universe.
Another case illustrated how matter and antimatter behave differently is the recent case of positronium
There is a novel explanation that I am particularly found of however: I propose that matter and antimatter are exactly mirror images of each other but that as a result of that opposite orientation that that can move differently and position themselves differently in the multiple curled up dimensions above and beyond the three extended spatial dimensions. Thus we creatures of matter are existing in space that incompletely intersects with the space that antimatter exists in, see only a small portion of the antimatter that exists and do not see the full extent of the antimatter we do see as some of it is poking into curled dimensions differently than our matter does.
These articles are simply speculation about the results of a future experiement. The New Scientist article goes on to explain that current theory expects that both types of matter will behave the same way in a gravitational field, and a spokesman for the experiment is quoted as being willing to bet that there will be no difference (although it would be exciting if there was).
We’re just saying that it would look the same, since our eyes detect CP-symmetry-respecting photons. You could certainly perform experiments that could tell anti-lead apart from lead, but I read the OP as meaning literally “What would it look like?” which, as far as we know, has the answer “the same”.
That article doesn’t show that matter and antimatter behave differently, but rather that we don’t understand something about how positronium interacts and breaks up when it encounters matter. It also suggests that we may need to work more on understanding positron-atom cross sections en route to a positronium-atom cross section understanding. (Positrons and electrons do, of course, have different scattering rates on the experimenters’ targets since the targets are made of matter.)