# Abusing E=Mc2 **URL:** \ **Category:** Factual Questions\ **Created:** [January 23, 2013, 12:09am UTC](https://boards.straightdope.com/t/abusing-e-mc2/648059 "2013-01-23T00:09:18Z")\ **Posts on this page:** 7\ **Page:** 3
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [January 24, 2013, 3:14pm UTC](https://boards.straightdope.com/t/abusing-e-mc2/648059/41 "2013-01-24T15:14:07Z")
> [@For You](#): > > Note that you may hear of “rest mass”: some particles have no mass when they are not in motion (gauge bosons, usually). As is constantly noted around these parts, the “mass” that is not “rest mass” (i.e. “relativistic mass”) is just a synonym for “energy” and is not really used as a term any more (like for the last several decades). Really we could rephrase the laws of physics referring to energy only: Objects resist acceleration when force is applied in proportion to their energy, and energy is the cause of gravitation. It just so happens that most of the objects we deal with in everyday life contain an imperial fuckton of energy even when they’re standing still, to the point where we can ignore any additional energy they have because of their motion or whatever when discussing their inertia or gravity. ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [January 24, 2013, 6:08pm UTC](https://boards.straightdope.com/t/abusing-e-mc2/648059/42 "2013-01-24T18:08:32Z")
> [@leahcim](#): > > As is constantly noted around these parts, the “mass” that is not “rest mass” (i.e. “relativistic mass”) is just a synonym for “energy” and is not really used as a term any more (like for the last several decades). Yep, it is not a good idea to have synonyms in physics. Mass is best thought of as the portion of energy that can not be ‘transformed away’ (i.e. by changing reference frames). ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [January 26, 2013, 9:46am UTC](https://boards.straightdope.com/t/abusing-e-mc2/648059/43 "2013-01-26T09:46:13Z")
> [@Chronos](#): > > On the first point, the basic reaction is two protons going in, and three protons and one antiproton coming out, so you do indeed have more matter (meaning the familiar sort, as opposed to antimatter) at the end than you started with. Thanks, that’s good to know. But most of the collisions don’t make matter/antimatter- they just make lots of short-lived particles which quickly decay into energy. I am only guessing, but it seems likely that the end tally would be a reduction of matter rather than an increase. My point is that there’s no practical way of turning energy into matter. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 26, 2013, 9:58am UTC](https://boards.straightdope.com/t/abusing-e-mc2/648059/44 "2013-01-26T09:58:11Z")
> [@eburacum45](#): > > … short-lived particles which quickly decay into energy… 😕 ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [January 26, 2013, 11:38am UTC](https://boards.straightdope.com/t/abusing-e-mc2/648059/45 "2013-01-26T11:38:16Z")
Well, yes, I think so; the main product of these proton interactions are pions, which decay into electrons and energy. It would be interesting to weigh the products that come out and the products that go in, to see what the balance is. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 26, 2013, 4:04pm UTC](https://boards.straightdope.com/t/abusing-e-mc2/648059/46 "2013-01-26T16:04:59Z")
Actually, once the dust settles and you’re left with stable particles, you’ll never decrease the number of protons, or at least it happens so incredibly rarely that you’d need to run your accelerator for many lifetimes of the Universe for it to happen. One of the near-absolute conservation laws followed by particle interactions is the conservation of baryon number, and protons are the lightest particle that has a nonzero baryon number. When you collide two protons together, the most common reactions will in fact give you a bunch of pions which eventually decay away to lightweight particles (some combination of electrons, positrons, neutrinos, and photons), but they will _also_ give you two protons. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [January 26, 2013, 9:48pm UTC](https://boards.straightdope.com/t/abusing-e-mc2/648059/47 "2013-01-26T21:48:34Z")
I see. Hmm. Even if you make an antiproton and annihilate one of the starting protons, you’ve also made another proton to replace it. Sounds like these high-energy collisions convert energy into matter on a small scale after all. [Previous page](https://boards.straightdope.com/t/abusing-e-mc2/648059.md?page=2)