Energy into Matter??

[Pomlom]

Hello,

 

I know that matter can be turned into energy(E=+/-mc^2). Can the opposite be true too??? Energy into matter???

 

Pomlom

[rbp6]

Of course.

[timo]

Probably most known effect: Pair production: Photon -> electron + positron.

 

Problems might arise with your definition of energy and matter and their differences. For example: Photon. Is it energy or matter?

[Severian]

Traditionally 'matter' has been defined as the particles apon which forces act while the gauge bosons which mediate the forces are not considered matter (this is a bit of an arbitrary distinction though). Using that definition, a photon is not 'matter', but an electron is (with a positron being anti-matter).

 

In fact, the theory of the big bang has all of matter being created in this way, eg [math]\gamma \to e^+ e^-[/math]

 

Notice that in the above reaction there an equal amount of matter (e-) and anti-matter (e+) are created and this is the case in (almost) all reactions. So if it was all created in the big bang, this implies that there should be (almost) an equal amount of matter and antimatter in the universe. But looking around us, nearly everything is matter and there is very little antimatter to be found! One of the big questions in science right now is how do we reconcile the big bang with the absence of anti-matter. (The is the problem of the Baryon Asymmetry of the Universe.)

[swansont]

Notice that in the above reaction there an equal amount of matter (e-) and anti-matter (e+) are created and this is the case in (almost) all reactions. So if it was all created in the big bang, this implies that there should be (almost) an equal amount of matter and antimatter in the universe. But looking around us, nearly everything is matter and there is very little antimatter to be found! One of the big questions in science right now is how do we reconcile the big bang with the absence of anti-matter. (The is the problem of the Baryon Asymmetry of the Universe.)

 

Just last week it was announced that there were new findings in CP violations in B meson decay, with large asymmetries in the matter vs. antimatter decays - much larger than previously seen in Kaon decays.

[harsh]

well i am a lil confused ...is it rite to say that when we look at a body we can see it due to light energy , so is this light energy arising from the conversion of the matter into light energy?? if its true then if we can stop light will beget converted into the same matter again??

[Aeschylus]

[math]\gamma \to e^+ e^-[/math]

 

The above formula for the case of a photon in a vacuum is impossible as it violates four momentum.

 

What you are looking for is something like this:

 

[math]\gamma\gamma \to e^+ e^-[/math]

[swansont]

[math]\gamma \to e^+ e^-[/math]

 

The above formula for the case of a photon in a vacuum is impossible as it violates four momentum.

 

True, but that's the reaction that happens near a nucleus. The nucleus recoil preserves momentum.

[Severian]

well i am a lil confused ...is it rite to say that when we look at a body we can see it due to light energy , so is this light energy arising from the conversion of the matter into light energy??

 

No - what you are seeing when you look at something is light from some external source reflecting off the body. Otherwise you would see it in the dark. (Actually, light is being constantly emitted in the infra-red, since the objects are warm, but not at a wavelength you can see.)

[swansont]

No - what you are seeing when you look at something is light from some external source reflecting off the body. Otherwise you would see it in the dark. (Actually, light is being constantly emitted in the infra-red, since the objects are warm, but not at a wavelength you can see.)

 

And the whole radio spectrum, and more - blackbody radiation is a continuum. It's just peaked in the IR for what we consider "warm."

[ydoaPs]

energy and matter are different forms of ths same thing, so i'd say it would happen. actually, it does happen.