I What turns energy into matter and vice versa?

[physics user1]

How does the universe decide if transforming energy into matter or vice Versa?
Is there a particle or a field that decides so?
Is a probability process?

 

[Orodruin]

Energy is not a substance that transforms into matter. Energy is a property of matter, just like momentum or mass.

 

[physics user1]

Energy is not a substance that transforms into matter. Energy is a property of matter, just like momentum or mass.

OK, maybe I said it wrong, with matter I was meaning mass

 

[Orodruin]

OK, maybe I said it wrong, with matter I was meaning mass

Yes, the answer is still the same. There is nothing being converted. Just energy changing form from some other form of energy to energy in the form of mass. This is no stranger than energy changing from potential energy to kinetic energy.

 

[physics user1]

Yes, the answer is still the same. There is nothing being converted. Just energy changing form from some other form of energy to energy in the form of mass. This is no stranger than energy changing from potential energy to kinetic energy.

Yes, but what decide whenever to convert or not?
For example why doesn't all the mass around us convert in another form?

 

[Orodruin]

You might as well ask why kinetic energy is converted into potential energy. It happens in nature and we have physical theories that describe how this occurs in a very good manner.

The answer is that nature simply foes not behave in that way. If you want a "deeper" answer you are no longer asking s physics question.

 

[physics user1]

The answer is that nature simply foes not behave in that way. If you want a "deeper" answer you are no longer asking s physics question.

Ok, thanks, so there's not a field or something in quantum mechanics theory that mediate this conversion process and "decides" how much is converted or not

 

[Khashishi]

I think what you meant to ask is what turns photons into matter and vice versa. Both photons and matter have energy.
If that is the case, photons can turn into matter and antimatter in a process called pair production. And matter and antimatter can become photons in a process called annihilation. There is a certain probability of the former happening if a high enough energy photon hits matter. And a certain probability of the latter happening whenever a matter and antimatter particle are close to each other. The probabilities are given as cross sections--the larger the cross section, the more likely they are to react (or interact). The probabilities depend on which particles are interacting, and can involve lengthy calculations to compute.

It's almost certainly possible to collide two photons to produce an electron and positron, but rather difficult to demonstrate in a lab due to the low probability and high energy gamma rays needed.

 

[physics user1]

I think what you meant to ask is what turns photons into matter and vice versa. Both photons and matter have energy.
If that is the case, photons can turn into matter and antimatter in a process called pair production. And matter and antimatter can become photons in a process called annihilation. There is a certain probability of the former happening if a high enough energy photon hits matter. And a certain probability of the latter happening whenever a matter and antimatter particle are close to each other. The probabilities are given as cross sections--the larger the cross section, the more likely they are to react (or interact). The probabilities depend on which particles are interacting, and can involve lengthy calculations to compute.

It's almost certainly possible to collide two photons to produce an electron and positron, but rather difficult to demonstrate in a lab due to the low probability and high energy gamma rays needed.

You got the point, thanks, so it's a matter of probability that something turn into energy? For example in nuclear decay is there a probability that when the nucleus decays some mass turns into photons? It is possible to know before how much of its mass turn into photons?

 

[Zafa Pi]

Ok, thanks, so there's not a field or something in quantum mechanics theory that mediate this conversion process and "decides" how much is converted or not

There is. The vase is sitting on the shelf Schrodinger's cat pushes it off thus converting potential energy to kinetic energy. Quantum mechanics does it again.

 

[physics user1]

There is. The vase is sitting on the shelf Schrodinger's cat pushes it off thus converting potential energy to kinetic energy. Quantum mechanics does it again.

So... there is a field, does the field act based on probability or is something that can be easily predicted, for example in a nuclear decay, can we predict the products of the decay and the mass that has transformed in photons?

 

[BvU]

You got the point, thanks, so it's a matter of probability that something turn into energy? For example in nuclear decay is there a probability that when the nucleus decays some mass turns into photons? It is possible to know before how much of its mass turn into photons?

Decay goes from higher mass to lower - the difference goes into kinetic energy and rest energy of the other decay products. Nuclear decay tables are full of half-life and decay product energies info.

 

[physics user1]

Decay goes from higher mass to lower - the difference goes into kinetic energy and rest energy of the other decay products. Nuclear decay tables are full of half-life and decay product energies info.

But how can we predict these products? (Theoretically I mean)

 

[Khashishi]

For a reaction to occur, it has to obey certain conservation laws, such as angular momentum conservation, momentum conservation, energy conservation. It usually also obeys approximate conservation laws like lepton number, baryon number, etc. To make a prediction, you have to list all the possible reactions, and calculate their probabilities. I can't help you with the details there.

 

[Tanelorn]

How might a photon create, perhaps with other constituents, a proton?

Can other bosons create fermions?

 

[Khashishi]

Yes, other bosons can create fermions.

As far as how, two photons come together and, bang, a proton and an antiproton come out. You have various Feynman diagrams depicting possible pathways for the reaction, but what actually happens is some superposition of possible pathways. You can't say exactly what happens between what goes in and what comes out.

 

[Tanelorn]

ok thanks I didn't know that Protons were also possible, I thought it was only electron positron pairs.
So it is theoretically possible to collide photons as a way of making a proton source?

 

[Khashishi]

All particles are theoretically possible, as long as various conservation laws are obeyed. Theoretically possible, but not practical.

 

[Tanelorn]

Thanks, it really makes one realize that every form of matter and energy is made of the same thing just in a different form.
And it all started with a maximum density, homogeneous form of matter/energy right at the start of the BB.

 

[vanhees71]

?

 

[tionis]

I have a question: did the inflaton field create particles or just inflated the universe?

 

[Tanelorn]

?

Van, was talking about the quark gluon plasma described half way down this excellent article
http://www.forbes.com/sites/startsw...n-where-did-the-big-bang-happen/#4e7c03977c0f