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 Subject: Pure Energy...Yes or No? Category: Science > Physics Asked by: davidetal1234-ga List Price: \$5.00 Posted: 02 Mar 2005 19:19 PST Expires: 01 Apr 2005 19:19 PST Question ID: 483779
 ```I thought there was no pure energy becuase Absolute Zero has never been reached....until I read this: " If a positron and an electron collide at low speed (so there is very little kinetic energy) they both disappear in a flash of electromagnetic radiation. This can be detected and its energy measured. It turns out to be 2m0c2 where m0 is the mass of the electron (and the positron). Thus particles can "vaporize" into pure energy, that is, electromagnetic radiation. The energy m0c2 of a particle at rest is called its "rest energy". Note, however, that an electron can only be vaporized by meeting with a positron, and there are very few positrons around normally, for obvious reasons-they just don't get far". This quote is a a cut and paste from http://galileo.phys.virginia.edu/classes/252/mass_and_energy.html. So, is electromagnetic radiation 'pure energy', or does it contain at least some Mass? David``` Request for Question Clarification by hedgie-ga on 07 Mar 2005 20:01 PST ```idetal1234-ga we did cover 'annihilation of e- and e+' into emg and agreed that emg is closest thing to 'pure energy', but still has a 'relativistic mass' in answer 1, did we not? So, in your series on 'pure' energy: Nature of Energy and Matter 15 Feb 2005 5 comments \$10.00 E=MC2 simplified 20 Feb 2005 20 comments \$5.00 Pure Energy...Yes or No? 02 Mar 2005 4 comments \$5.00 your comment in question 2, http://answers.google.com/answers/threadview?id=477866 This seems terribly important to me. I understood from it that we cannot (yet) explain exactly *how* one form (eg: E) converts into another form (M), but all we understand is that it does, and does so at C2 and even more question 3, seems a bit like a regression (step back). It all reminds me quote attributed to Einstein: "Everything should be as simple as possible, but not more simple" So far, we all did sin by trying to make it 'more simple', I think. To grok the answer to understand the m*c*c and that .. in does not require to study math for ten years, but it requires more than one \$5 paragraph. It requires understanding the concepts 1) Physical quantity (motion) 2) Frame of reference (relativity) 3) amalgamation of quantities (as e.g. electro-statics plus magneto-statics => emg) each would require at least a page of explanation and some Socratic dialog - I would guess each would be a \$200 ga answer. Ideally, on would recommend a book - and that perhaps would be a \$10 ga search to find a best textbook for this. Question is how much time, effort and expense you want to expend to reach what level of understanding. Hedgie```
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 Subject: Re: Pure Energy...Yes or No? From: biophysicist-ga on 03 Mar 2005 11:20 PST
 ```Yes, electromagnetic radiation is pure energy. Electromagnetic radiation is made out of photons, which are massless.```
 Subject: Re: Pure Energy...Yes or No? From: davidetal1234-ga on 03 Mar 2005 18:50 PST
 ```Thanks v. much biophysicist. Is there also 'pure mass'? Also, I thought that light was made of photons. If it is, and photons have no mass, then why light bent by the sun? Does gravity affect 'pure energy'? thanks again. David```
 Subject: Re: Pure Energy...Yes or No? From: drmikem-ga on 05 Mar 2005 10:19 PST
 ```Good questions! Photons are massless only when they are at rest (not moving, zero rest mass). Photons move at the speed of light of the medium they are in. Photons transfer energy and must have some energy. They can be though of as pure energy, or carriers of pure energy. When electrons and positrons (anti-electrons) annihilate, they produce pure energy which is release by the creation of two photons (gamma rays of about .5 Million electron volts of energy each). They travel in opposite directions, so there is not net momentum created. This matter-antimatter annihilation is the most pure way that matter can be converted into energy and just energy. The reason that the quotation mentioned the low temperature (low kinetic energy, means moving very slowly) is that they were illustrating that mass, alone, can be converted into pure energy. If the electron and positron were moving before the energy of their motion, the kinetic energy, is also carried away by the created photons and adds to the photons energy. They would then have the energy from their kinetic energy included with the energy from their rest mass. In a nuclear reactor, on a small fraction of the mass is converted into energy. The uranium atoms break apart into parts that have less mass than the original atoms; this lost mass is released as energy. In fact, the released energy is the energy required to hold the atom together. So, matter-antimatter annihlation is the most pure and simple illustration of the conversion of mass into energy, or E=mc^2. About the light bending around objects with mass: They do have a mass using the same relationship E=mc^2. So they are affected by gravity! However, the best way to think of it is from Einstein's Theory of General Relativity which described the photons path as being "straight:, but that space is warped by the presence of the massive object. I'd have a bit of trouble explaining that much more.```
 Subject: Re: Pure Energy...Yes or No? From: wyop2005uc-ga on 05 Mar 2005 18:27 PST
 ```The question is not whether pure energy can exist, but rather what is mass? Energy is the fundamental quantity that does exist, while mass is just a concentration of energy. (E=mc^2). Gravity therefore does not actually act between masses, but between energy. Photons do not have mass, but they do carry energy and hence can be attracted by gravity. Any particle that has mass can not move at the speed of light, hence photons have no mass, whether they are at rest or not. As for absolute zero, it can never be reached because it is impossible for the fundamental particles to become completely motionless. Heat is the energy caused by motion of individual particles. It is impossible to precisely know both the position and momentum of a given particle, and if it stops at one point we would be able to measure both.```
 Subject: Re: Pure Energy...Yes or No? From: moesi-ga on 13 Mar 2005 09:24 PST
 ```Funnily, if "a" photon has enough energy (about 1022MeV = 2x 511 MeV, that is the "mass" of one electron/positron) it can break up into an electron/positron pair without any reason. By the way, "pure" ist a poor word. Mass ist eqaul to enery.```
 Subject: Re: Pure Energy...Yes or No? From: qed100-ga on 14 Mar 2005 08:10 PST
 ```Hello, A particle/anti-particle pair may anihilate, resulting in a burst of massless photons, but it's not really accurate to say that the photons are 'pure' energy, any more than were the original pair of massive particles. It is, generally, a 'parameter' of a particle, which characterises, places constraints upon, how it will interact with another particle. A particle 'has' energy. It isn't energy itself. I'll illustrate this with the way energy is related to momentum in special relativity. In SR a particle traces what is called its 'worldline' through space-time. In a simple two dimensional space-time there are two axes, (x,t), with x being space, t being time. Each point on the t axis is a tick of the clock, so to speak. If a particle in this system is traveling at some speed through space, then for each value of t, the particle occupies a different value of x, a different place in space. If it's traveling at the speed of light, c, then it changes one unit of x for each unit of t, and so it traces a straight path at 45 degrees to both axes. If it's at less than c, then the path makes a smaller angle with t. As the particle's speed approaches zero, its angle with t also approaches zero. At zero speed it's not moving through space- but interestingly enough, it's still tracing through the t dimension. Energy is related to the way things change in time, and momentum to the way they change in space, e.g.: A wave has both frequency & wavelength. In quantum mechanics, a particle has an associated wave. The frequency is a function of the particle's energy, the wavelength of its momentum. In SR, energy corresponds to the t component of a particle's space-time path. Momentum is the x component. It's clear to see then that even for a particle with zero speed(zero 'kinetic' energy, zero momentum), it still has energy, because it still has an umambiguous t component in space-time. A particle has energy because it exists. It isn't 'made of' energy.```
 Subject: Re: Pure Energy...Yes or No? From: davidetal1234-ga on 14 Mar 2005 17:37 PST
 ```Hedgie This is getting clearer for me. In layman's (ok: lay person's) terms, there is a ball rolling down the hill. We - us people - see this and we call the ball Mass, and we call the 'moving' Energy. But the ball is just a unity, a one-thing, which does not know from E and M, far less that E=M! Put another way, we create abstractions, and then look at the abstractions. It is the same as me looking in a mirror and mistaking the reflection of reality for reality itself. E and M (along with C^2) are abstractions; reflections in the mirror. We are tempted to treat them as real (we certainly see them - in the word-idea-mirror) but although we distinguish them in our minds, they do not exist as distinct things in reality. Another way of saying this is "E and M are two manifestations of the same thing", to quote Einstien directly, or, mathemetically, E=M by a factor of a Very Big Number (such as speed of light times itself). At least, that is my current take on all this. It is nice to have this verified insofar as I have yet to read any incontravertable (read: 'simple') proof that E does exist 'just by itself' independent of Mass. This tells me, at least, that these are 'reflections in the mirror of the mind' rather than actual realities in their own right. yeah?!?! onwards...! David```
 Subject: Re: Pure Energy...Yes or No? From: hedgie-ga on 15 Mar 2005 10:27 PST
 ```David I am happy that it is becoming more clear and I do see some signs of that. We have agreed that emg (=electromagnetic radiation) is close to the un-exact, common language expression, "pure energy". Then come other bosons, such as mesons and neutrinos, which can be considered more 'pure' then fermions such as electron and positron. So, I disagree with qed100-ga who says " ..photons are NOT 'pure' energy, any more than were the original pair of massive particles.." In some sense they are. But I am sorry that I have to say 'NO' to your ' yeah?!?! '. It is not like that. As I outlined in RFC, it is more complex than that. If you want more explanation from me, you need to respond to the RFC, knowing that it is not a yes/no issue. Some concepts are needed in order to undestand E=m*c*c. Energy and mass are two different quantities, according to one theory. They are two ways of talking about the same quantity acording to another theory. The two theories (Newton's vs Einstein's mechanics) are both useful - and so - both valid in their realms. I suggest, if you really want to understand this, that you ask for a book suggestion, indicating how much time and effort you want to give it, as well what level of math you can tolerate. Hedgie```
 Subject: Re: Pure Energy...Yes or No? From: qed100-ga on 15 Mar 2005 11:36 PST
 ```Hello hedgie-ga, I also have to kindly disagree that Bosons are more 'pure' energy than are Fermions. Even if one were to propose that Bosons are more elementary as particles than Fermions(which, at least within the Standard Model, they aren't), being a more primitive particle wouldn't make them 'be energy'. Yes, work must be done on a field in order to pop out a stable particle/anti-particle pair, i.e., it takes an expenditure of energy to make matter. But the particles are a symptom of the energy(or rather, a resultant of a mode of interaction), not the energy itself.```
 Subject: Re: Pure Energy...Yes or No? From: hedgie-ga on 15 Mar 2005 20:21 PST
 ```qed (Quantum Electro Dynamics)? You certainly are entitled to your opinion (since we agree that 'pure' is a word with no exact definition - both views are just an opinion). But I wonder if you have read the beginning of the saga: http://answers.google.com/answers/threadview?id=475235 where we (David and I) agreed on one possible meaning of the word pure: " Other way to interpret the question is in terms of current elementary particle theory. e.g. : there are photons - particles of light - which are hard to put into a test-tube (less impossible, lately) but hard. and there are things made of atoms,like water and air, which go well into the test tube..." Bosons are not 'more elementary' (whatever that means) but fact remains that electrons are source of the (emg) field and not the other way around. So there is some 'ordering' in the sense of http://mathworld.wolfram.com/Poset.html Respectfuly Hedgie```