Antimatter

[Agelesslink]

I was reaseaching radiation after reading the radiation and astronauts thread and i came across the term antimatter and looked it up on wiki. i understand that antimatter negates matter, but what blows my mind is when it was stated that there can be places comosed entirely of antimatter. my mind cannot imagine what this place would look like. when i think of an absence of matter, i think of space. is antimatter the same thing as the absence of matter. can someone shed some light on antimatter and what it would look like to a layman?

i wish i had gone to college in physics

[davew]

Have a listen to this. It may interest you.

BBC - BBC Radio 4 Programmes - Big Bang Day: Five Particles, The Antiparticle

Dave.

[Agelesslink]

thanks Dave! i have a better idea of what antimatter is. i figure the main goal of research of antimatter is its energy properties, but i can't help but wonder what a cup of anti H2O would look like. if it would quench my thirst. silly things like that.

[FraserClarke]

i can't help but wonder what a cup of anti H2O would look like. if it would quench my thirst. silly things like that.

It would look entirely the same as normal H2O...

I wouldn't drink it though -- would have bad consequences for you, your throat, and the surrounding continent...

[Matthew.Blake]

It would look entirely the same as normal H2O...

I wouldn't drink it though -- would have bad consequences for you, your throat, and the surrounding continent...

In fairness to the antimatter though, we annihilate it as much as it annihilates us. It's got a bit of a bad rap these days, everyone assuming it's the evil one!

[FraserClarke]

In fairness to the antimatter though, we annihilate it as much as it annihilates us. It's got a bit of a bad rap these days, everyone assuming it's the evil one!

Indeed. One can argue that antimatter is the heavily persecuted minority in the Universe!

[Capricorn]

All anti-matter is are particals that are charged opposite to what we are used to.

This universe has stabilised to the state we call normal matter.

No reason why we are not composed of "anti-matter". Perhaps over an average of 100,000,000 universes a proton with what we call a negative charge and electron with a positive charge may be the majority or normal state. So we would then be considered to be composed of anti-matter.

[Bried]

I suppose you could say that anti-matter is matter and matter is anti-matter. After all they are only labels that we have given so we know what they are.

Brian

[661-pete]

Nowadays, I think, most cosmologists agree that there aren't whole stars, or galaxies, composed of antimatter. Which is rather a shame, we have to leave the imagined repercussions to the SF writers!

I remember an amusing general 3rd-year exam question in Particle Physics, that we worked through in tutorials. Simply put, imagine that Earth has established contact with beings on a distant planet, in another galaxy (forget the time-lag!); assume these beings are as advanced in Physics as we are. The question is: devise a set of experiments to determine whether they are matter or antimatter. We are communicating purely by electromagnetic waves.

Electromagnetic experiments won't do, because you can't describe, or agree with the aliens as to which is the 'north' pole of a magnet.

So a non-parity-conserving weak interaction then. Measure the helicity of the neutrino, by one of the 'standard' experiments. If they get the same answer as us, they are matter; otherwise, antimatter. Problem is, you have to explain to the aliens what you mean by 'right-handed' and 'left-handed'.

Someone suggested polarising the radio waves we send to the aliens. But that's cheating.

The correct answer was a bit advanced, involving performing a CP-violating experiment of some sort. I can't remember the details now, and probably wouldn't understand them any more.

This was all in the 1960s before we had the Standard Model. Presumably there would be better answers now. But I found it fascinating.

[FraserClarke]

The correct answer was a bit advanced, involving performing a CP-violating experiment of some sort. I can't remember the details now, and probably wouldn't understand them any more.

In Frank Close's book 'Antimatter' (which is a nice overview for non-particle-physicists) he suggests the decay rate of the K0 meson as a discriminator. This is slightly more like (0.3%) to produce positrons rather than electrons, so gives you a way to tell if you're made of matter (your atoms have electrons in them) or anti-matter (your atoms have positrons in them).

[E621Keith]

Anti-matter is really just matter with the opposite charge, and they obey the same law of physics like normal matter. Matter and antimatter do annihilate each other on contact, which is why they don't last very long in the matter universe. I guess the opposite occur in the antimatter universe, matter get destroyed when they meet the antimatter. However, the occupant of the antimatter universe can live in pretty much the same way as us in the matter universe.

[rabbithutch]

Right! Of course!

If antimatter is particles with the opposite atomic structure - which is what I 'think' I understand of all this - what is dark matter?

I think I have some, but I'm not sure as it's hiding in a black hole and I can't shed any light on it. ::insert ducking and running smilie here ::

Actually, we have recently been adopted by a black cat who I've named Dark Matter. She can sit in front of our tall speakers that are covered in black grille cloth and disappear. I'd take her picture but she reflects no light . . . :: insert the second one here::

[Earl]

what is dark matter?

To quote a iTunes U i watch recently.

"Answer that and you will be famous"

afaik Dark Matter and Dark Energy are unproven things which came into "theory" to balance an equation, probably a very long complicated one at that.