Does Antimatter exist in the universe anymore?

[Nova]

If Antimatter was completely annihilated after the Big Bang, how is it that we have studied it. As well as artificially created it? If we can't create normal matter, why would we be able to create antimatter? And since we can, why doesn't it immediately get annihilated from the contact of the matter?

 

[mathman]

Positrons are antimatter (widely used in medical devices). Antimatter has been created in laboratories.

 

[SteamKing]

If Antimatter was completely annihilated after the Big Bang, how is it that we have studied it. As well as artificially created it? If we can't create normal matter, why would we be able to create antimatter? And since we can, why doesn't it immediately get annihilated from the contact of the matter?

It depends on what you mean by 'create' matter. We can certainly transmute elements by using atom smashers, and there are nuclear reactions in which antimatter can be created momentarily before it annihilates with regular matter. What is difficult to do is to contain and accumulate significant quantities of antimatter with current technology.

 

[DennisN]

If Antimatter was completely annihilated after the Big Bang, how is it that we have studied it. As well as artificially created it? If we can't create normal matter, why would we be able to create antimatter? And since we can, why doesn't it immediately get annihilated from the contact of the matter?

Hi Nova! There is an ongoing collaboration called ALPHA which studies antimatter;
Home page: http://alpha.web.cern.ch/
How Alpha works: http://alpha.web.cern.ch/howalphaworks
And a clip from that page, showing some of the equipment:


EDIT:
This clip was better (description of equipment and techniques):

 

[Drakkith]

The simple fact is that we can create both matter and antimatter. We do this all the time in particle colliders.

And since we can, why doesn't it immediately get annihilated from the contact of the matter?

If we say "shortly" instead of "immediately", then it usually does. The exceptions are when we store antimatter in order to study it.

 

[e.bar.goum]

Not only do we routinely create matter and antimatter in particle accelerators, and store it in traps or rings, it's important to note that antimatter is created by nature all the time. Nuclei that are proton rich compared to stable nuclei decay via positron - anti-electron - emission!

Linked is a chart of all known nuclei, the number of protons are on the y axis, the number of neutrons on the x axis. The black squares are the stable isotopes, and everything that is coloured pink is a nucleus that decays via positron (β⁺) emission. http://upload.wikimedia.org/wikipedia/commons/7/79/NuclideMap_stitched_small_preview.png

 

[Orodruin]

In addition to what has already been said, we are also constantly bombarded with anti-matter in cosmic rays. For example, the AMS-02 experiment has measured the positron fraction in the electron and positron cosmic ray flux (see, e.g., http://www.ams02.org/wp-content/uploads/2013/03/Press_2.jpg). Between 5 and 15 percent of the total flux is positrons, depending on the energy you are looking at.

 

[e.bar.goum]

Also, there is the suggestion that to solve the baryon asymmetry problem, you can have large portions of the universe composed of antimatter, as opposed to matter. It's not a terribly popular view, and it's not supported by some observational evidence, but it's not completely laughable either.

 

[Chronos]

The original photon-baryon ratio of the early universe is totally dependent on matter - antimatter annihilations.

 

[Tejaslion]

wouldn't helium be a better option than hydrogen? you get to study even anti neutrons..

 

[phinds]

wouldn't helium be a better option than hydrogen? you get to study even anti neutrons..

Who are you quoting? That is, who SAID it is hydrogen? I'm not finding that in the thread. Please use the quote button. Thanks.

 

[Chronos]

Anti matter is created continuously in the universe, just not in large quantities and it tends not to escape annihilation for very long. In the very early universe it is believed to have been almost as abundant as regular matter. There was, however, an imbalance that permitted a relatively miniscule amount of regular matter to survive annihilation. The reason for this is a mystery. All we know is it occurred before atoms had a chance to form.

 

[Nova]

The simple fact is that we can create both matter and antimatter.

But antimatter and matter share the same properties right? So wouldn't it not make sense due to law of conservation?

 

[Orodruin]

Generally, antiparticles have the same mass as their corresponding particles, but carry opposite quantum numbers (such as electric charge). Assuming that you have enough available energy and momentum to create the particle-antiparticle pair, no conservation laws are being violated.

 

[vela]

But antimatter and matter share the same properties right? So wouldn't it not make sense due to law of conservation?

What would make sense? Conservation of what?

 

[nuuskur]

I keep seeing the word "create" over and over again. It is counter-intuitive. We should not be able to create matter, it exists and we are allowed to shape it, transform it, but not create it.

 

[Drakkith]

I keep seeing the word "create" over and over again. It is counter-intuitive. We should not be able to create matter, it exists and we are allowed to shape it, transform it, but not create it.

That is simply not correct. Matter can be created and destroyed and it happens all the time. There's nothing counter-intuitive about it.

 

[robotpie3000]

That is simply not correct. Matter can be created and destroyed and it happens all the time. There's nothing counter-intuitive about it.

But matter is destroyed, its converted into energy via E=mc² right?

But antimatter and matter share the same properties right? So wouldn't it not make sense due to law of conservation?

Just like what others said, it depends on the law of conservation of what. The law of conservation of charge holds because the particle-antiparticle pair have the same charge magnitudes but with opposite polarity (eg +e for a positron and -e for an electron). An annihilation of a particle-antiparticle pair does maintain conservation of energy and linear momentum, but the opposite phenomenon, called pair production (where a photon materializes into a particle-antiparticle pair), there must be a nearby massive object (eg. a nucleus) to maintain the law of momentum and energy conservation. The nucleus must be involved to carry away part of the initial photon momentum.

 

[Nugatory]

I keep seeing the word "create" over and over again. It is counter-intuitive. We should not be able to create matter, it exists and we are allowed to shape it, transform it, but not create it.

Google for "pair production" - this is the process by which energy on the form of photons turns into an electron and an anti-electron.

 

[phinds]

But matter is destroyed, its converted into energy via E=mc² right?

Wrong. That is the theoretical maximum energy that can be extracted if you could create a 100% efficient process. Atom bombs, for example, as WAY far from 100% When matter is forced to change states, it is converted into many things, energy just being one of the possible ones, and it is usually as light and heat and other forms of matter. The heat is, I think, the main energy that one thinks of in atom bombs although there's a lot of light as well. I'm not sure what kind of particles are left over from the blast.

 

[robotpie3000]

Wrong. That is the theoretical maximum energy that can be extracted if you could create a 100% efficient process. Atom bombs, for example, as WAY far from 100% When matter is forced to change states, it is converted into many things, energy just being one of the possible ones, and it is usually as light and heat and other forms of matter. The heat is, I think, the main energy that one thinks of in atom bombs although there's a lot of light as well. I'm not sure what kind of particles are left over from the blast.

Ah thanks for that correction. So when a particle and its associated antiparticle collide and annihilate, only the "lost" mass is converted into energy, and the rest into the other forms you mentioned?

 

[mfb]

An annihilation releases all the energy in the particles - the particles get annihilated and stop existing. 100% lost mass, sort of.

Nuclear weapons are not annihilation reactions, you transform atoms into different atoms. A tiny fraction (like 0.1% for fission) of their total energy gets released and the products have nearly the same mass of the original atoms (~0.1% less).

 

[phinds]

Ah thanks for that correction. So when a particle and its associated antiparticle collide and annihilate, only the "lost" mass is converted into energy, and the rest into the other forms you mentioned?

Sorry, I was only talking about conversion. As mfb correctly pointed out, annihilation DOES release all of the energy

 

[Dryson]

How much anti-matter and matter would be required to create a Big Bang?

 

[Drakkith]

How much anti-matter and matter would be required to create a Big Bang?

The big bang was not an explosion. It was an expansion of space which resulted in a gradual reduction in the temperature and density of the universe over the past 13 billion years. In other words, the big bang was not a single explosive event, but a process of expansion.

You cannot create a big bang by annihilating matter and anti-matter.

 

[Dale]

You cannot create a big bang by annihilating matter and anti-matter.

Well, you could in principle make a large bang, and even a big bang, but not a Big Bang. Luckily scientific language is so precise ;)

 

[Monsterboy]

What is the difference in terms of spectrum ? Imagine you have isolated some element of antimatter and analysed it's spectrum (say anti-hydrogen) will it be same as normal matter hydrogen spectrum ?

If we find a distant galaxy made completely of antimatter , which is sufficiently away from other normal matter galaxies to avoid annihilation, will our telescopes be able to tell us that it's made of antimatter ?

 

[mfb]

What is the difference in terms of spectrum ? Imagine you have isolated some element of antimatter and analysed it's spectrum (say anti-hydrogen) will it be same as normal matter hydrogen spectrum ?

It should be the same, and several experiments are testing this with increasing precision (one example).

If we find a distant galaxy made completely of antimatter , which is sufficiently away from other normal matter galaxies to avoid annihilation, will our telescopes be able to tell us that it's made of antimatter ?

We should certainly see the boundary regions between antimatter and matter where annihilation would happen.

 

[Bandersnatch]

We should certainly see the boundary regions between antimatter and matter where annihilation would happen.

Hannes Alfven in his, now very much dated, 1966 book Worlds-Antiworlds: Antimatter in Cosmology argued that initial annihilation at the boundary would create enough of radiation pressure to push the two kinds of matter apart and subsequently reduce the annihilation rate below detectable levels. I don't remember if he had any calculations there, it's been some years since I've read it. Still, the point can be made that this particular argument can be reasonably circumvented.

There are of course other serious issues with the picture, including the lack of a mechanism to separate matter and antimatter in bulk, but this one is not such a strong one.

 

[mfb]

Hannes Alfven in his, now very much dated, 1966 book Worlds-Antiworlds: Antimatter in Cosmology argued that initial annihilation at the boundary would create enough of radiation pressure to push the two kinds of matter apart and subsequently reduce the annihilation rate below detectable levels. I don't remember if he had any calculations there, it's been some years since I've read it. Still, the point can be made that this particular argument can be reasonably circumvented.

There are of course other serious issues with the picture, including the lack of a mechanism to separate matter and antimatter in bulk, but this one is not such a strong one.

Well, that just opens up more questions. Where are those large surfaces without matter (of either kind)? Where are the antihelium nuclei AMS-02 is looking for?

We cannot fully rule out that model, but large amounts of antimatter look very problematic in many aspects.