If scientists managed to make a solid block of antimatter that they would be able to visually see in front of them, would they actually be able to see it if light were shown upon its surface and reflected? I=Or is the light from anti-matter different somehow. Maybe we can't answer it right now because we don't have a visible clump of entire anti-matter atoms...

If scientists managed to make a solid block of antimatter that they would be able to visually see in front of them, would they actually be able to see it if light were shown upon its surface and reflected? I=Or is the light from anti-matter different somehow. Maybe we can't answer it right now because we don't have a visible clump of entire anti-matter atoms...

 

 

You would expect anti-matter to emit anti-photons.

 

Of course, since a photon and an anti-photon are the same thing, you would not notice a difference.

 

Since anti-matter will tend to annihilate with ordinary matter, there would be a LOT of photons.

 

You would notice a really bright light. But not for very long.

Perhaps the folks trapping antihydrogen will be able to measure the index of refraction of their sample. But right now that would be a tough measurement.

You would expect anti-matter to emit anti-photons.

 

Of course, since a photon and an anti-photon are the same thing, you would not notice a difference.

 

Since anti-matter will tend to annihilate with ordinary matter, there would be a LOT of photons.

 

You would notice a really bright light. But not for very long.

 

Well I'm not talking about when they annihilate each other, I'm talking about just anti-matter on its own. Photons don't carry any charge that I know of, so I expect their photons from quantum leaps to be the same as normal matter, but I don't know for sure.

Perhaps the folks trapping antihydrogen will be able to measure the index of refraction of their sample. But right now that would be a tough measurement.

 

I'm not eve sure what "index of refraction" means when applied to a handful of atoms.

I'm not eve sure what "index of refraction" means when applied to a handful of atoms.

 

That's why I think it would be a tough measurement. But it should vary continuously with density, so it's a matter of having a sensitive enough measurement and enough atoms.

How many atoms does one need to define an index of refraction? Does the cluster of atoms need to be at least a few incoming wavelengths thick? I imagine scattering causes problems here.

 

Its an intetesting questions because it has implications about where we draw the "bulk material" line.

Gases have an index of refraction, and it's dependent on how many atoms you have. You can put a gas cell in one arm of a Michelson interferometer and watch the fringes shift as you pump it out or pressurize it. The problem is that even at STP, the index is only around 1.001. The number of atoms they've trapped mean that the value will be suppressed by many orders of magnitude.

Will it soon be possible to run qualitative / comparative experiments - ie whilst sample size might be too small to get measurements that in absolute terms are useful; could you not create two identical magnetic holding volumes one with hydrogen and one with anti-hydrogen and identify differences (or lack of) between the two samples. with interferometry would you be able to notice a change in interference pattern where one route ran through a hydrogen containment and the other ran through anti-hydrogen - or would even this qualitative view be swamped out?

Will it soon be possible to run qualitative / comparative experiments - ie whilst sample size might be too small to get measurements that in absolute terms are useful; could you not create two identical magnetic holding volumes one with hydrogen and one with anti-hydrogen and identify differences (or lack of) between the two samples. with interferometry would you be able to notice a change in interference pattern where one route ran through a hydrogen containment and the other ran through anti-hydrogen - or would even this qualitative view be swamped out?

It depends on the sensitivity of the interferometer to the sample. The problem is the change in the optical thickness of the material is small because the sample doesn't have many atoms in it. With a normal gas sample you can compensate by making the cell longer of you need to. Doing a difference measurement of hydrogen and antihydrogen would be harder, since then you are presumably trying to measure zero, or a signal that is statistically significant from zero if there's new physics.

Why would you expect anti-matter to behave any differently with respect to electromagnetic phenomena. An atom would consist of anti-protons and anti -neutrons surrounded by a cloud of positrons with eqivalent ( to regular matter ) energy levels. Anti-matter has charge and intrinsic spin reversal and since EM force is not 'handed' ( ie doesn't violate parity ), there is no difference. Anti-matter can also be handled mathematically as regular matter moving backwards through time, such that emission and absorption of a photon, although reversed in sequence, happen exactly the same.

Why would you expect anti-matter to behave any differently with respect to electromagnetic phenomena. An atom would consist of anti-protons and anti -neutrons surrounded by a cloud of positrons with eqivalent ( to regular matter ) energy levels. Anti-matter has charge and intrinsic spin reversal and since EM force is not 'handed' ( ie doesn't violate parity ), there is no difference. Anti-matter can also be handled mathematically as regular matter moving backwards through time, such that emission and absorption of a photon, although reversed in sequence, happen exactly the same.

I don't. But you still need to test these things.