matter/antimatter anihilation

jadibartolomeo · Sep 2, 2005

is the tenet that matter can neither be created nor destroyed no longer valid because of the discovery of matter/antimatter anihilation and creation? the only reason i can come up with is that matter is not "created" or "destroyed" but converted either from energy to matter or from matter to energy. i'm sure one of you has a better answer <img src="/images/icons/smile.gif" /> thanks.

vogon13 · Sep 2, 2005

There are several conservation laws that come into play in matter/antimatter reactions. Conservation of net electric charge is observed. Conservation of baryon number is observed. IIRC, gamma radiation of the appropriate energy has been observed to generate matter/antimatter particle pairs in the reverse of the process. (electrons and positrons at least, I don't know if protons and/or neutrons and their antimatter counterparts have been studied in this regard.) <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

tomnackid · Sep 2, 2005

MASS & ENERGY cannot be created or detroyed (on average). Ever since e=mc^2 we have kown that "matter" and "energy" are really just two states of the same thing. You can think of mass as being a measure of the total energy locked up inside this thing we call "matter". I say mass & energy cannot be created or destroyed "on average" because ever since quantum theory and the uncertaintly principal we know that it is perfectly possible for mass/energy to spontaneously pop into existence out of nowehere (out of the vacuum) or disappear into the vacuum. But it happens be creating equal amounts of positive and negative mass/energy wich then recombine to form nothing before interacting with the rest of the universe. The total mass/energy balance remains the same. If this happens near the even horison of a black hole one particle in the pair can cross the event horizon and efectively "leave" the universe, its conterpart is now "promoted" to a real particle with positive mass/energy. The net effect is that it looks as if the black hold is emeiting particles of matter and enegy (Hawkning Radiation). But you can't get something for nothing unfortuantely. By absorbing particles of negative energy the black hole loses mass until it evaporates--all the books are balanced.

vogon13 · Sep 2, 2005

IIRC, a recent article in Sci Am stated that over half of what we percieve as 'weight' is in actuality energy of motion of the constituent gluons and quarks. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

jadibartolomeo · Sep 2, 2005

forgive me, i'm new at this. i'm reading a book on quantum mechanics right now, so i'm trying to absorb as much as i can. from what i understand, the uncertainty principle states that we can never precisely measure two properties of a quantum system simultaneously, like position and momentum or energy level and duration of said energy. so how does the uncertainty principle allow matter pop in and out of existence? vogon, just today i was learning about quarks and the constituent particles. memorizing electrons, protons, neutrons, pions, and the many flavors of quarks has overwhelmed me! btw, what does IIRC mean? i see it a lot on here. thanks for the replies, guys.

Saiph · Sep 2, 2005

well, how much energy does a vacuum have? Can't say zero (energy level is fuzzy too)...so there's some. how much? for how long? how often? and one way to explain the "vacuum fluctuations" that heisenberg suggests, is virtual particles. they occur when the vacuum hits that incredibly breif, high energy state, and then disappear before they can do anything (remember, heisenberg can be implied to mean you get away with anything, so long as you don't get caught). <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

vogon13 · Sep 2, 2005

If I Recall Correctly (IIRC) I tend to use it a lot. One effect of becoming an old fart. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Sep 2, 2005

By the way (BTW), I rarely google stuff, its (to me, only) a form of cheating, if I don't know, I don't post, if I'm not sure, I'll (IIRC). If I am speaking infallibly, I leave out the (IIRC). (some times I put in stuff to stir the pot too, have fun deciding when I'm doing that) <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

yevaud · Sep 3, 2005

In Free Space, Ditto, as far as the "stirring the pot" goes. But I'm usually straight on in the science forums. Get stuff wrong once in a while. Memory's not quite what it was. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

Saiph · Sep 3, 2005

steve, Heisenberg also addresses the energy of a particle, and the duration of that energy state. Applying that to the "vacuum" state, and you give rise to the possibility of virtual particles. Heisenberg does play a role with them. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

Saiph · Sep 3, 2005

No, that says the Uncertainty principle can be applied to the size vs duration of an energy state... And that this leads to the idea of virtual particles. Like I've been saying. But that is a neat little page. Thanks steve. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

contracommando · Sep 3, 2005

"so how does the uncertainty principle allow matter pop in and out of existence?" Particles, in quantum mechanics, are allowed to do so as long as they annihilate each other and go back out of existence almost immediately. They same applies to particles receiving extra energy, as long as they lose it quickly-that process is called quantum tunneling. Experimentally, we know this to be correct-but I’m not sure exactly how this occurs (not sure many do). I do know, however, that it is necessary and occurs in places like our sun; and the effects might be observable around the event horizons of black holes (at least in theory).

cuddlyrocket · Sep 4, 2005

The Uncertainty Principle as normally stated is that (delta p) x (delta x) = a constant (where p is momentum, x is position and (delta p) is the uncertainty or error in the value of p etc.). Now momentum has units of mass times velocity. Mass has units of Energy divided by velocity squared (E=m.c.c), and velocity itself is distance divided by time. So: (delta p)(delta x) = (delta m)(delta v)(delta x) = (delta E/v.v)(delta v)(delta x) = ((delta E)/(delta v)(delta v))(delta v)(delta x) = (delta E)(delta x)/(delta v) = (delta E)(delta x)/((delta x)/(delta t)) = (delta E)(delta t). So the energy of a system can vary but only for a certain amount of a time. So for example, an electron and positron can both come into existence, but they can only remain in existence for a small amount of time. Such particles are called virtual particles. It should be noted though, that whilst they exist, such particles are just as real as any other electron or positron. So if there was a 'permanent' electron passing nearby when this pair came into existence, it would be influenced by their electric charges, and such interactions have to be taken into account when calculating paths and properties etc. Also, although an electron and positron must annihilate within the specified time, it doesn't have to be the same electron and positron. In our example, the positron could annihilate with the 'permanant' electron, thereby 'prmoting' the virtual electron to permanent.

tomnackid · Sep 6, 2005

"The existence of virtual particles popping in and out of existence has nothing to do with Heisenberg. It's a quantum physics observation which was found to be experimentally confirmed by the Casimir effect. The two are quite separate." ------------------------------------------------------------------------------------------ Steve, the existence of virtual particles and "vacuum energy" are a direct implication of the uncertainty principal. If I were to say the a certain volume of space was completely empty I would be making the assertion that there were zero particles with zero location with zero momentum and zero energy. The uncertainty principal says I cannot say that. In fact the uncertainty principal implies that given enough time ANYTHING could spontaneously pop into existence. Of course the PROBABILITY of something like say a Dodge Viper sports car (one can dream!) suddenly appearing out of nowhere is so remote that it would take many millions of times the projected life span of the universe to occur. Photons (and there negative energy counterparts) on the other hand are appearing and disappearing all the time.

cuddlyrocket · Sep 7, 2005

"Photons (and there negative energy counterparts) on the other hand are appearing and disappearing all the time." I know that photons are their own anti-particles, but what is the negative energy counterpart of a photon? More generally, the Energy/Time uncertainty principle is always illustrated by virtual particles popping into and out of existence - a (temporary) increase in total energy. But the uncertainty principle is symmetric - decreases in total energy are just as likely as increases. When you get a decrease , what is the physical realisation of this?

Saiph · Sep 7, 2005

An anti-particle isn't a "negative" energy counterpart...really it's just the opposite charge (and a few other properties). As for the negative energy parts of "vacuum" energy, the idea is the energy required for the "positive" events that create (or doesn't create) particles is borrowed from the surroundings, and those surroundings are the negative events. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

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