Does antimatter look different?

[MC.STEEL]

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.

[Padishar]

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)...

[Ralathon]

The appearance of an object depends mostly on the electron shells. Metals look shiny because their outermost electrons are free to wander about and objects have colors because atomic bonds absorb certain wavelengths.

Since antimatter has the exact same weight and the exact same (but opposite) charges the visual characteristics are the exact same. So in a perfect vacuum you are unable to see the difference between iron and antiiron based purely on reflected or emitted light.

Here's the catch though, 'perfect vacuum'. Even interstellar space contains plenty of stuff. The solar wind pumps out 1e9 kg/s of matter. At 1AU this means your antimatter gets bombarded with 3.5e-15 kg/(m^2*s). So your antimatter will emit about 630 watts of energy per square meter facing the sun due to annihilation at the surface. It should be trivially easy to measure this unexpected energy with the proper equipment. Most of the energy is going to get dumped as hard Gamma or neutrinos, but depending on the medium you might be able to see some Cherenkov radiation with the naked eye.

[*Aqua*]

Can we really see antimatter? We see stuff because it reflects light or emits light on its own.

Antimatter can't reflect lights. Photons will cause explosions if it comes into contact with it. (That's what I believe.)

Does antimatter emit 'anti-emissions' when it is heated? If yes, we can't see it, the emissions will destroy every sensor or eye.

[Ralathon]

Can we really see antimatter? We see stuff because it reflects light or emits light on its own.

Antimatter can't reflect lights. Photons will cause explosions if it comes into contact with it. (That's what I believe.)

Does antimatter emit 'anti-emissions' when it is heated? If yes, we can't see it, the emissions will destroy every sensor or eye.

What you believe is wrong.

Antimatter only annihilates when it comes into contact with its normal counterpart. A positron and a proton could snuggle without issues, but a positron plus an electron would destroy each other. Antimatter isn't made out of antilight (infact, light is its own antiparticle) so light mixes just fine with antimatter. We often use light to trap antimatter using optical tweezers in fact.

[*Aqua*]

Light is its own antiparticle? Weird. Thanks, I didn't know that.

Does that apply to all EM radiation?

[Doozler]

Light is its own antiparticle? Weird. Thanks, I didn't know that.

Does that apply to all EM radiation?

Yup. Also some of the other "force carriers"

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

[Ralathon]

Light is its own antiparticle? Weird. Thanks, I didn't know that.

Does that apply to all EM radiation?

Yes, it does. All EM radiation is essentially the same, the only difference is the wavelength. Radiowaves consist of photons with a wavelength of a few km, (red) light has a wavelength of about 0.6 micrometer and gamma radiation has a wavelength of a few nanometers.

[GreatWyrmGold]

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)...

Of course, since the reaction would start when the astronaut's glove brushed the anti-ferrium, a whole gram might not react.

Light is its own antiparticle? Weird.

Welcome to advanced science.

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

Well, [abbr=In My Humble and Uninformed Opinion]IMHaUO[/abbr], it makes sense that antimatter would be repulsed from matter. If it was, that easily explains why all the matter and antimatter did not annihilate each other before either could form any kind of structure.

[Padishar]

Of course, since the reaction would start when the astronaut's glove brushed the anti-ferrium, a whole gram might not react.

Though if a gram is equivalent to 21 kilotonnes then 1 microgram would be equivalent to 21 kg of TNT and I wouldn't want that going off anywhere near me, let alone in my hand...

Also, when annihilating in this way you have to add the mass of the normal matter, so you're doubling the energy released...

[KerikBalm]

Since gravitational attraction is a property of mass, and anti-matter still has mass, why wouldn't there be a gravitational attraction.

Antimatter is essentially the same set of particles, with opposite charges, right (perhaps this is oversimplified), but I can't imagine why there would be gravitational repulsion, unless we were talking negative mass-mass.

Furthermore, can't such things be measured already?

[SargeRho]

So far, I think only nanograms are stored at any given time. That's not enough to see if it's attracted or repelled by gravity.

[Brenok]

Since gravitational attraction is a property of mass, and anti-matter still has mass, why wouldn't there be a gravitational attraction.

Antimatter is essentially the same set of particles, with opposite charges, right (perhaps this is oversimplified), but I can't imagine why there would be gravitational repulsion, unless we were talking negative mass-mass.

Furthermore, can't such things be measured already?

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.

[TheGatesofLogic]

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. If antimatter had a gravitational repulsion from normal matter then it would be expected that light, because it is it's own antiparticle, would have to propagate asymmetrically with respect to these fields, and this leads to several interesting phenomena which potentially violate many known laws, including causality in certain situations. Current understanding predicts that antimatter would appear exactly like normal matter except when in the presence of its opposite, leading to some interesting astronomical phenomena which have yet to be onbserved if the universe created antimatter and matter in equal parts, such as annihilation spectra barriers in intergalactic space due to the mixing cosmic winds of particle and antiparticle pairs.

Edited April 2, 2014 by TheGatesofLogic

[magnemoe]

Though if a gram is equivalent to 21 kilotonnes then 1 microgram would be equivalent to 21 kg of TNT and I wouldn't want that going off anywhere near me, let alone in my hand...

Also, when annihilating in this way you have to add the mass of the normal matter, so you're doubling the energy released...

Interesting, so if using antimatter dust as a minefield in space it would be more effective against fast moving targets, more particles would react before blowing apart, kind of like an chain reaction

[Rakaydos]

Interesting, so if using antimatter dust as a minefield in space it would be more effective against fast moving targets, more particles would react before blowing apart, kind of like an chain reaction

Interstellar dust (or the containment device to keep intersteller dust out) gives all the mass the antimatter needs.

[nhnifong]

Wouldn't antimatter also annihilate with virtual pairs and emit something like hawking radiation?

[Brotoro]

Wouldn't antimatter also annihilate with virtual pairs and emit something like hawking radiation?

If there is a virtual pair, then there is energy that needs to be 'paid back' for the creation of the pair (and paid back quickly. Quantum mechanical loan sharks are fierce). If your particle annihilated with a virtual particle, that energy would go back to paying for the creation of the pair in the first place...and all you'd have left is the other particle from the pair (exactly like the one you started with)... and no radiation.

[KerikBalm]

So far, I think only nanograms are stored at any given time. That's not enough to see if it's attracted or repelled by gravity.

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.

Edited April 2, 2014 by KerikBalm

[78stonewobble]

Sure it is... thats what a mass spec does.

If Antimatter "fell up", then it would have negative deflection in a mass spec, no?

Of course, there would be other ways, but a mass spec illustrates the principle that you don't need a lot.

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.

To be honest tho I don't think anyone's dropped any kind of antimatter dumbbell, without a boatloat of magnetic fields affecting everything, but yeah, antimatter should, as far as I've read, behave like normal matter except for the opposite charge.

[Ralathon]

Sure it is... thats what a mass spec does.

If Antimatter "fell up", then it would have negative deflection in a mass spec, no?

Of course, there would be other ways, but a mass spec illustrates the principle that you don't need a lot.

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.

A mass spectrometer measures mass (Hence the name). Interaction with gravity causes weight, which is the thing we're interested in. The deflection in a mass spectrometer is caused by a magnetic field after all, not a gravitational field.

Most physicists are pretty sure it'll fall down like normal though. If it acted any other way you get some strange predictions that we don't see in nature. For example, light is its own anti particle, so if you have have a lightbeam run through a gravitational field you'd expect the beam to split in half. 1 half would curve following towards the mass and the other would curve the other way. But we don't see this when we look at gravitational lenses in astronomy.

Another good reason is that it allows you to build a perpetuum mobile. If antimatter falls up and matter falls down it should be entirely free to move a particle-antiparticle pair up or down in a gravity well. But light gains energy when it moves down a gravity well. So if you make a particle pair, lift it a couple of kilometers before you annihilate and then capture the released light lower in a gravity well you've gained free energy from nothing.

[FenrirWolf]

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. If antimatter had a gravitational repulsion from normal matter then it would be expected that light, because it is it's own antiparticle, would have to propagate asymmetrically with respect to these fields, and this leads to several interesting phenomena which potentially violate many known laws, including causality in certain situations. Current understanding predicts that antimatter would appear exactly like normal matter except when in the presence of its opposite, leading to some interesting astronomical phenomena which have yet to be onbserved if the universe created antimatter and matter in equal parts, such as annihilation spectra barriers in intergalactic space due to the mixing cosmic winds of particle and antiparticle pairs.

That last part gave me a random thought of a hypothetical pair of neighboring star systems with their own intelligent species, but one of the star systems is matter and the other antimatter. They could send messages to each other with EM radiation, but don't try to arrange a meetup!

[N_las]

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.

The problem is that you have to cool the animatter down enough. If its to hot, the velocity of the positrons is way to high to see any effect of gravity. To cool positrons down, one shots them into a metal. It is a misconception, that they will annihilate instantaniously. A large number of positrons will leave the metal at a lower temperature, because they lost energy by colissions with regular matter in the metal.

Imagine they would have room temperature after that. That would mean a velocity of 1.1*10^5 m/s. If the free fall along a 100 m horizontal vacuum tube, they will have a vertical displacement of 4 µm. But after 100 m the positron beam would have a very big radius in the order of meter. So it is impossible to measure if they went up or down.

Especially if you consider that the smallest electric charge in the area of the experiment would displace the beam much farther.

[K^2]

One can set up an antimatter fountain. It will probably be done soon enough. But nobody seriously expects to see repulsion. There are all sorts of problems with that, many of which we should have seen symptoms of by now.

There is every indication that antimatter behaved exactly as matter does, to within some chirality corrections in weak interaction. Even that is just matter of handedness.

[Dispatcher]

Perhaps antimatter will have a strange color of charm.