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Is energy convertible to matter?

  1. May 21, 2013 #1
    Can we convert energy to matter?
     
  2. jcsd
  3. May 21, 2013 #2

    Dale

    Staff: Mentor

    No, but we can convert photons to matter, which may be what you actually wanted to ask.

    Energy is a property, not a "thing".
     
  4. May 21, 2013 #3
    Yes! We do it on a regular basis, actually. In particle colliders like LHC, two particles are accelerated until they have a lot of kinetic energy, you smash them together, and you end up with a whole bunch more particles than you started with.
     
  5. May 21, 2013 #4
    And that property allows you to produce more matter since particle number isn't conserved in QFT. I don't understand your point.
     
  6. May 21, 2013 #5

    BruceW

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    Homework Helper

    typically you are going to have particles becoming other particles. I think this is what DaleSpam means.
     
  7. May 21, 2013 #6
    Einstein's Energy Equation E=mc2. Can we write the reverse equation as
    m=E/c2 ?
     
  8. May 21, 2013 #7

    Dale

    Staff: Mentor

    You can convert things with energy (e.g. a pair of photons) into other things with energy (e.g. an electron and positron). Energy doesn't exist by itself, so you cannot simply convert energy (without an accompanying thing) into matter.

    This is important because any of the things that have energy also have other properties, such as spin, or momentum, or charge, etc.
     
  9. May 21, 2013 #8

    Dale

    Staff: Mentor

    Yes.
     
  10. May 21, 2013 #9

    Dale

    Staff: Mentor

    Certainly, and you can write E/c=mc, and you can write E/m=c², and you can write mc²/E=1, and any other permutation I may have missed. You can add a constant to both sides, square both sides, do whatever you like. All of the normal rules of math apply.
     
  11. May 21, 2013 #10

    BruceW

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    Homework Helper

    yes. as long as 'm' stands for relativistic mass. In essence, c^2 is just a conversion of units. you can even use natural units where c=1, so that E=m i.e. relativistic mass is just another word for energy.

    Also, there are two other concepts: rest mass and invariant mass. These are different from the relativistic mass, and follow other equations.
     
  12. May 21, 2013 #11
    Thank you Dalespam I got the idea.. I did'nt know energy is a property still now.
     
  13. May 21, 2013 #12
    BruceW,thanks
     
  14. May 21, 2013 #13
    yes, energy can be condensed to mass.
     
  15. Oct 18, 2015 #14
    I would like to see all permutations and the meaning. Like C=√e/m
    Is this the reason we cannot get matter to light speed?
     
  16. Oct 18, 2015 #15

    Dale

    Staff: Mentor

    It is related. The formula ##E=m c^2## is the formula for the energy of a system whose momentum, ##p=0##. In other words, it is the energy at rest.

    For a system which is moving the more general formula is ##E^2/c^2=m^2 c^2+p^2##. For a massive particle ##p=mv/\sqrt{1-v^2/c^2}## which goes to infinity as v goes to c.
     
  17. Oct 18, 2015 #16
    The meaning is the same, that rest energy and mass are equivalent. Two things that were previously thought to be different are instead the same.

    You see the phrase "matter is converted to energy" as an explanation for things like the explosion of a uranium bomb where there is a reduction in mass equivalent to a production of energy. The point of the mass-energy equivalence, though, is that the energy was there all along, we just didn't recognize it as energy. We recognized it as mass. Thus the notion of mass being a measure of the amount of matter has to be abandoned. But the very phrase "matter is converted to energy" is a remnant of that now-abandoned notion.

    This conversion of mass to energy is not unique to nuclear explosions. The same thing happens in a camp fire, but the reduction in mass is too small to be measured, so previous notions (notions that mass and rest energy are different things) ignored it. Indeed, how is one supposed to not ignore something one cannot detect?!

    No. It's rather the other way around. The postulate is that light speed is the same to all observers. So if you, as an observer, were to chase after a light beam you'd never make progress because you would forever see it recede from you at light speed. It therefore follows that you can never attain light speed. And the mass-energy equivalence also follows from that same idea. It's all based on the Principle of Relativity, something that dates back to the time of Galileo. Einstein is famous for incorporating the propagation of light into that principle, and in the process coming up with the mass-energy equivalence.
     
    Last edited: Oct 18, 2015
  18. Oct 18, 2015 #17
    You bet. One example is that when the concentration of energy becomes very high it sort of congeals into an electron-positron pair.
     
  19. Oct 19, 2015 #18
    I understand that at speed of light, mass go infinite and time should collapse. It will need infinite power to move one gram at light speed. A backwards mirror would may show slow motion or all time compress. I did not look at this.
    Can you transform e=mc^2 and isolate c. What this equation mean, in static or moving form.
    I may missing knowledge. But square of speed of light is a big speed.
    Seem to work on atom level.
    It is easier to understand pi since you can calculate it easy with any circle
     
  20. Oct 19, 2015 #19
    No. One example is: a table has some lenght. Can we "convert lenght in a table?" Of course not. In the same way "a portion of matter has some energy, so we cannot convert energy into matter".

    --
    lightarrow
     
  21. Oct 19, 2015 #20

    Dale

    Staff: Mentor

    You can do this, but it doesn't change the meaning at all. This is off topic for this thread, if you want to discuss rearrangements of formulas more then please start a new thread. But I don't anticipate that you will get anything interesting since it doesn't change the meaning.

    I am going to go ahead and close this thread.
     
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