Does antimatter look different?

[Doozler]

ugh, it is a very small portion of the scientific community that supports antimaterial gravitational repulsion, and the reason for this involves light being it's own antiparticle.

I will defer to your superior knowledge on this matter! The comment came because I had just read the below article on measuring the gravitational acceleration of anti-hydrogen for the first time at LHC:

http://www.theregister.co.uk/2014/03/31/cern_team_uses_gpus_to_discover_if_antimatter_falls_up_not_down/

I probably should have replaced "not sure if antimatter fall down" with "not experimentally verified that antimatter falls down"

[lajoswinkler]

Theoretically there is no reason why antimatter should look any different to normal matter, however, a chunk of antimatter of a visible size would do significantly more than blow his fingers off. One gram of antimatter being annihilated would liberate slightly more energy than the Fat Man atomic bomb used in WWII (21 kilotonnes)...

Not neccessarily.

The contact between two lumps is only on the surface. They would effectively blow themselves apart and away from each other upon touching in vacuum. It would be a very ineffective reaction. Only if someone would introduce a lump of antimatter on Earth would a grand explosion result, because matter is everywhere.

[TarkinLarson]

Wouldn't antimatter look and behave "normally" (like matter does in our normal universe) in an 'anti' universe (ie: one that was made of more antimatter than matter, the reverse of ours).

But again, being as light is also it's own anti-particle, you would not need anything special to see antimatter... as light would react with it as if it was matter. Surely?

[TarkinLarson]

I've done a little Googling to find out about light being an anti-particle of itself, and this was a very good academic link which explains it quite well and concisely if anyone is interested...

http://van.physics.illinois.edu/qa/listing.php?id=1153

[Guest]

Wouldn't antimatter look and behave "normally" (like matter does in our normal universe) in an 'anti' universe (ie: one that was made of more antimatter than matter, the reverse of ours).

Due to certain symmetries, it wouldn't do. You'd also have to reverse the time and swap left with right for it to behave exactly the same (it's called "CPT theorem"). It's actually a very interesting matter, so to speak. Consider the implication that we wouldn't be able to tell an positron moving backwards in time from an electron. What is all electrons in the universe are, in fact, a single electron going back and forth in time? This is actually a serious theory, though it's obviously a bit more complicated than that.

Light would be just fine for observing antimatter. It shouldn't really look different from normal one.

Edited April 3, 2014 by Guest

[Z-Man]

Not neccessarily.

The contact between two lumps is only on the surface.

Unfortunately, no. Two lumps of matter can only touch at the surface, true. That is, essentially, because the Pauli exclusion principle forbids two electrons to be in the same state, so the electron shells of lump 1 can't go where the shells of lump 2 are.

If Lump 2 is antimatter, however, things are different. The Pauli principle does not apply, the shell positrons already are in an intrinsically different state. Matter and antimatter can penetrate.

They still get blown apart once the reaction starts, you will probably say. Well, not small blocks. What happens next is that some electrons and positrons annihilate into gamma rays. Gamma rays are highly penetrating, they quickly leave the immediate area and do not blow apart the lumps.

And once only a small fraction of positrons and electrons are gone, what you have is a massively negatively charged lump of antimatter and a massively positively charged astronaut. The lump of antimatter will immediately be pulled entirely into the astronaut's hand where the rest of the positrons are eliminated. That's already 0.05%-0.1% of the total mass converted into gamma rays, again escaping without blowing anything up.

I'm not familiar enough with strong interactions and the relevant cross sections to say what happens to the nuclei once they find each other (which takes longer than the electron positron reaction because they are heavier). Maybe some (anti)nucleons annihilate on first contact and the recoil blasts the nuclei apart; in that case, still at least 2% more of the mass is converted into energy. Maybe before the first annihilation takes place, the entire two nuclei first penetrate each other (again, they're allowed to), in that case, energy conversion can be close to complete for identical elements of matter and antimatter.

[TarkinLarson]

Due to certain symmetries, it wouldn't do. You'd also have to reverse the time and swap left with right for it to behave exactly the same (it's called "CPT theorem"). It's actually a very interesting matter, so to speak. Consider the implication that we wouldn't be able to tell an positron moving backwards in time from an electron. What is all electrons in the universe are, in fact, a single electron going back and forth in time? This is actually a serious theory, though it's obviously a bit more complicated than that.

Light would be just fine for observing antimatter. It shouldn't really look different from normal one.

Oh man I love chats like this. This is one of the great things about the KSP community.

My mind has been blown... this is really interesting and am enjoyed keeping up with some of this conversation at least at a basic level. Time travelling electrons! It makes you realise how big and amazing the universe really is... even at a particulate scale. The thing that really entertained me is that you can smash two photons into each other, that have no mass, and they can produce something with mass, at the cost of energy (so keeping the whole thing constant overall). It really just reminds me to think of matter/energy rather than have them as two different things.

Would your reversing the antimatter's spin and other issues with the symmetry actually form a 'mirror' universe. Kerbals with goatees?

[MC.STEEL]

Oh man I love chats like this. This is one of the great things about the KSP community.

My mind has been blown... this is really interesting and am enjoyed keeping up with some of this conversation at least at a basic level. Time travelling electrons! It makes you realise how big and amazing the universe really is... even at a particulate scale. The thing that really entertained me is that you can smash two photons into each other, that have no mass, and they can produce something with mass, at the cost of energy (so keeping the whole thing constant overall). It really just reminds me to think of matter/energy rather than have them as two different things.

Would your reversing the antimatter's spin and other issues with the symmetry actually form a 'mirror' universe. Kerbals with goatees?

This is the very apex of "I know that i know nothing".

[AntiMatter001]

I have been pondering If antimatter is visually different from the regular stuff?

Like say you have a chunk of antiFerrum in space and an astronaut decides to grab it thinking its regular metal.Only to have his fingers blown off by the resulting reaction.

(For this experiment i assume that there are such chunks of antimatter floating in space).

While in atmo the violent reaction with the air is a dead giveaway.

well i'm pretty sure i'm not THAT voilitile but then again i wouldn't suggest poking me... i do pass pretty bad gas. XD

(this is meant as some comic relief guys... don't get all realism on my shizzle plz)

[SargeRho]

It is even more volatile than that. Part of it will annihilate before you touch it, from protons trapped in the magnetic field.

[lajoswinkler]

Unfortunately, no. Two lumps of matter can only touch at the surface, true. That is, essentially, because the Pauli exclusion principle forbids two electrons to be in the same state, so the electron shells of lump 1 can't go where the shells of lump 2 are.

If Lump 2 is antimatter, however, things are different. The Pauli principle does not apply, the shell positrons already are in an intrinsically different state. Matter and antimatter can penetrate.

They still get blown apart once the reaction starts, you will probably say. Well, not small blocks. What happens next is that some electrons and positrons annihilate into gamma rays. Gamma rays are highly penetrating, they quickly leave the immediate area and do not blow apart the lumps.

And once only a small fraction of positrons and electrons are gone, what you have is a massively negatively charged lump of antimatter and a massively positively charged astronaut. The lump of antimatter will immediately be pulled entirely into the astronaut's hand where the rest of the positrons are eliminated. That's already 0.05%-0.1% of the total mass converted into gamma rays, again escaping without blowing anything up.

I'm not familiar enough with strong interactions and the relevant cross sections to say what happens to the nuclei once they find each other (which takes longer than the electron positron reaction because they are heavier). Maybe some (anti)nucleons annihilate on first contact and the recoil blasts the nuclei apart; in that case, still at least 2% more of the mass is converted into energy. Maybe before the first annihilation takes place, the entire two nuclei first penetrate each other (again, they're allowed to), in that case, energy conversion can be close to complete for identical elements of matter and antimatter.

I'm pretty much sure a significant part will be heated so strongly that it immediately turns to plasma and scatters around. The collision will obviously not produce gamma rays only. This is macroscopic lump, solid state physics, not particle physics. Electrons and positrons are bound into clouds, and the lumps possess a molecular or ionic structure. They aren't free pointy particles colliding as in an accelerator.

[Z-Man]

I'm pretty much sure a significant part will be heated so strongly that it immediately turns to plasma and scatters around. The collision will obviously not produce gamma rays only.

The electron-positron reaction, which happens quicker, only produces gamma rays. What mechanism do you propose for the heating? The only energy you have available for the heating is the kinetic energy of the electrons. But that energy is only half the negative potential binding energy, and the electric binding energy of the nucleus-antinucleus is about the same initially and can go much, much higher (well, lower since it is negative) as the nuclei can pack themselves more densely now. Sure, individual nuclei can be ejected, but there is not enough energy available to completely scatter them in a way that prevents further annihilation.

You are right in one point, though: The state the matter/antimatter conglomerate is in can best be described as a plasma.

[K^2]

Z-Man, Pauli exclusion does not apply to electron-positron pairs as these are not identical particles. An electron and positron can share state, and there is no Pauli repulsion between the two.

[lajoswinkler]

Hmmm, let me get back to you, I'm gonna check this with someone more knowledgeable than me. It's an interesting topic.

[Z-Man]

Z-Man, Pauli exclusion does not apply to electron-positron pairs as these are not identical particles. An electron and positron can share state, and there is no Pauli repulsion between the two.

Yes, that's what I was saying, wasn't I? I may not have been overly clear.

It is, of course, entirely possible my entire prediction here is wrong. It's purely based on some rough arguments about energy and time scales and a lot of handwaving.

[lajoswinkler]

I contacted my physics guy and he can't tell. The question is pretty damn hard. Lone particles rushing at relativistic speeds in accelerators aren't systems of nucleons surrounded by lepton clouds, everything made into a cage.

I'm also sure there would be a difference between metal-antimetal collision and nonmetal-antinonmetal. The first pair has lepton gas, too.

[Z-Man]

I have to redact my attraction and total electron-positron annihilation claim. It doesn't work like that.

True, the matter and antimatter penetrate each other.

True, in the overlap zone, electrons and positrons annihilate, leaving a plasma of nuclei and anti-nuclei.

However, that plasma is overall electrically neutral and the leftover matter and antimatter are, too. So there is no reason for the electrons and positrons to leave their cozy spot. I was assuming they quickly redistribute over the whole former shape of the blob because... of reasons. That is silly, of course.

And without that, the rest of the process crumbles. The nuclei are free to react and certainly enough of them are hurled away from the plasma and into the leftover matter and antimatter and leave enough momentum there to blow everything apart.

[K^2]

I think, step one would be an either Perturbation Theory or simulation of an H-H-bar "molecule". I have no doubt that hydrogen and anti-hydrogen are going to interact. If they form a bound state, that's useful information. If they end up repelling, then we learn something too. Once we know how this system behaves, it's going to be a lot easier to understand how two chunks of matter and antimatter interact. Whether they tear into each other, or almost harmlessly bump into each other, with a small burst of radiation.

[How2FoldSoup]

Gravity is the weakest of all forces, you can't really measure it when there are forces 10^30 times stronger in place. Not on the scale where we have observed antimatter.

I've never seen any other force affect photons. That being said I wonder how the first experiments with antimatter and black holes will turn out. IE, what would happen if you dropped antimatter into a blackhole? Or other experiments with people much smarter than I can come up with.

[K^2]

IE, what would happen if you dropped antimatter into a blackhole?

Same thing that would happen if you drop in ordinary matter.

[Sirrobert]

A 1kg iron weight falls as fast as a 1000kg iron weight, all you need to do is see if these fall up or down.

Except that you can't do that when there are electromagnetic forces, that are WAY stronger, pulling on those nanagrams

I've never seen any other force affect photons.

Gravity is abit of an oddball among the forces.

The way I understand it, gravity is the weakest, but also has the furtest reach. So in the dept of space, there is only gravity to effect light

[Technical Ben]

Yup. Also some of the other "force carriers"

The interesting one is gravity- we're not 100% sure if antimatter falls up or down!

For obvious reasons it's considered to fall "down" as it's not a type of "anti-gravity". Though I suppose we could consider it travelling backwards in time, which could theoretically travel "up" when exposed to gravity. As gravity is very much a relativity related thing, I'd put a lot of money on antimatter being attracted positively to other matter (and it's self) via gravity. It's just one of those things that will be hard to observe.

Like we cannot observe the core of the moon to rule out it being made of cheese, but so far all evidence shows it's rock.

[K^2]

Gravity is abit of an oddball among the forces.

The way I understand it, gravity is the weakest, but also has the furtest reach. So in the dept of space, there is only gravity to effect light

Gravity has the same range as electromagnetic interaction. The difference is about the charge associated with the force. The relevant charge for gravity is the stress-energy tensor. So absolutely everything has gravitational charge. Electromagnetic forces are subject to electric charge, and there are plenty of electrically neutral particles. Photon being one of them. And in fact, it's true, that photon only carries gravitational charge. So gravity is the only force that will influence photon's propagation. Photon itself, however, it the gauge boson of electromagnetic force, so it will still interact with electrically charged particles.

On average, matter is neutral in all but gravitational charge. That's the main reason you see gravity having such a long reach.

[Sirrobert]

Gravity has the same range as electromagnetic interaction. The difference is about the charge associated with the force. The relevant charge for gravity is the stress-energy tensor. So absolutely everything has gravitational charge. Electromagnetic forces are subject to electric charge, and there are plenty of electrically neutral particles. Photon being one of them. And in fact, it's true, that photon only carries gravitational charge. So gravity is the only force that will influence photon's propagation. Photon itself, however, it the gauge boson of electromagnetic force, so it will still interact with electrically charged particles.

On average, matter is neutral in all but gravitational charge. That's the main reason you see gravity having such a long reach.

Well, even the things I thought I did understand in this topic are wrong.

So would that mean that, theoreticly, matter that is fully that is electrically charged would be effected by electromagnetic forces more than by gravity, while in space?

Or is there so much neutral mass 'emiting gravity (for lack of a better term that I know for it)', that that is the reason that gravity is the only force at those ranges?

[K^2]

There isn't a lot of electric field in most of the space, because matter is neutral on average. So it's not the question of how much it'd be affected. A charge particle on earth is affected by the same electric field in the same way as it is in space. But while gravitational fields far out in space can be significant, electric fields usually aren't.