# Could you build a hydrogen atom using only photons? **URL:** \ **Category:** Factual Questions\ **Created:** [March 23, 2013, 10:27pm UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772 "2013-03-23T22:27:20Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Qwertol](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Qwertol](https://boards.straightdope.com/u/Qwertol)\ **Post date:** [March 23, 2013, 10:27pm UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/1 "2013-03-23T22:27:20Z")
Is theoretically possible? Would it be possible with current technology? ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [March 23, 2013, 10:41pm UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/2 "2013-03-23T22:41:09Z")
I’d think you would at least need some hydrogen. ---
**Author:** ![D18](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@D18](https://boards.straightdope.com/u/D18)\ **Post date:** [March 23, 2013, 10:54pm UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/3 "2013-03-23T22:54:26Z")
Well, they did manage to create [matter at a much smaller scale.](http://www.bibliotecapleyades.net/ciencia/secret_projects/project077.htm) So maybe someday? ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [March 23, 2013, 10:59pm UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/4 "2013-03-23T22:59:50Z")
Not directly. [You could](http://en.wikipedia.org/wiki/Matter_creation) via photon-photon interactions in a dense photon gas by making protons, then cooling it down to create electrons, but it would take massive amounts of energy, and a large amount of luck to avoid the anti-particle pairs you generate (proton-antiproton, electron-positron) from annihilating and converting back to photons. Also, getting any left over particles to actually form hydrogen would be hard at the temperatures involved. Of course, you should get a slight excess of matter of over antimatter (simple theory predicts a 50/50 split, but matter in the universe exists so we know that the theory has some holes). You can show the generation of exotic massive particles (i.e particles with mass, not that they have lots of mass) from high energy photon collisions. So - theoretically possible. But not really practical, and very low yield. ---
**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:** [March 24, 2013, 12:23am UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/5 "2013-03-24T00:23:47Z")
If you want to do it without creating the same amount of antihydrogen, it’s not possible according to our current best theories: The Standard Model says that baryon number and lepton number are both conserved, and electrons have lepton number, and protons baryon number, but photons have neither. That said, most models that go beyond the Standard Model predict that it _is_ possible to violate conservation of lepton and baryon numbers, just extremely rare. In this case, it could be done, though at even greater difficulty than **si\_blakely** ’s antimatter suggestion. ---
**Author:** ![Qwertol](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Qwertol](https://boards.straightdope.com/u/Qwertol)\ **Post date:** [March 24, 2013, 6:58am UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/6 "2013-03-24T06:58:31Z")
But if there is always the same amount of matter and antimatter created, does it mean that if you turn matter into energy (photons) then after that it’s pretty much unrecoverable (you will get matter and antimatter that would eventually annihilate itself)? ---
**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:** [March 24, 2013, 8:23am UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/7 "2013-03-24T08:23:43Z")
Separate the proton and anti-proton quickly enough (and the electron and anti-electron) and you could in theory make both hydrogen and anti-hydrogen. We can’t do it today, but it might be something that will happen a lot in the future, as anti-hydrogen would be a useful fuel (if we can figure how to store it without it blowing up). ---
**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:** [March 24, 2013, 8:25am UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/8 "2013-03-24T08:25:41Z")
Here’s antihydrogen being stored for 1000 seconds [http://www.nature.com/nphys/journal/v7/n7/full/nphys2025.html](http://www.nature.com/nphys/journal/v7/n7/full/nphys2025.html) ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [March 24, 2013, 11:42am UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/9 "2013-03-24T11:42:14Z")
> [@Qwertol](#): > > But if there is always the same amount of matter and antimatter created, does it mean that if you turn matter into energy (photons) then after that it’s pretty much unrecoverable (you will get matter and antimatter that would eventually annihilate itself)? Thermodynamics, baby. Heat death of the universe. Well, we know it isn’t so. After the Big Bang, there were no massive particles, just a photon gas at incredible temperature and density. As the universe expanded and the gas cooled, it reached the range where photon collisions could produce matter/antimatter pairs. Here, the standard model predicts a 50/50 split, all the particles/antiparticles would annihilate and there would just be photons, no matter. But that didn’t happen. One of the extensions to the standard model was in play, and more matter than antimatter survived. There are researchers studying neutrino interactions/flipping to determine exactly how the standard model doesn’t fit, to illuminate future investigations into the nature of reality. One of the hopes for the LHC was that the Higgs Boson would not quite fit the Standard Model, thus indicating new physics. That didn’t happen, so people have to look elsewhere. But as of now, I can’t imagine any environments in the universe (aside from a few artificial research experiments) where photons could be persuaded to form particle/antiparticle pairs. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [March 24, 2013, 11:47am UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/10 "2013-03-24T11:47:25Z")
> [@eburacum45](#): > > Separate the proton and anti-proton quickly enough (and the electron and anti-electron) and you could in theory make both hydrogen and anti-hydrogen. > > We can’t do it today, but it might be something that will happen a lot in the future, as anti-hydrogen would be a useful fuel (if we can figure how to store it without it blowing up). No matter how useful antihydrogen would be as a fuel, any process to generate it is going to be so inefficient and energy-costly as to be completely impractical. You are looking at a photon gas with an average energy of 10[sup]13[/sup]K to produce protons/neutrons. The electron/positron experiment above had to achieve 10[sup]10[/sup]K. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [March 24, 2013, 12:13pm UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/11 "2013-03-24T12:13:53Z")
Couldn’t you do it near a black hole and hope some of the antihydrogen got sucked in, like how that happens with virtual particles? ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [March 24, 2013, 12:25pm UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/12 "2013-03-24T12:25:16Z")
> [@AaronX](#): > > Couldn’t you do it near a black hole and hope some of the antihydrogen got sucked in, like how that happens with virtual particles? The Black Hole is an equal opportunities sucker - it will suck in as many particles as antiparticles. ---
**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:** [March 24, 2013, 12:32pm UTC](https://boards.straightdope.com/t/could-you-build-a-hydrogen-atom-using-only-photons/653772/13 "2013-03-24T12:32:39Z")
> [@](#): > > Quoth **Qwertol** : > > But if there is always the same amount of matter and antimatter created, does it mean that if you turn matter into energy (photons) then after that it’s pretty much unrecoverable (you will get matter and antimatter that would eventually annihilate itself)? All processes are reversible. In just the same way that you can’t convert a bunch of photons into matter without also producing antimatter, you also can’t convert matter without antimatter entirely into a bunch of photons. > [@](#): > > Quoth **AaronX** : > > Couldn’t you do it near a black hole and hope some of the antihydrogen got sucked in, like how that happens with virtual particles? Sure, that’d work: A black hole is one situation where we know for a fact that the Standard Model doesn’t hold up. A black hole that’s been fed matter is indistinguishable from one that’s been fed antimatter (as long as the charge is the same, which it would be for whole hydrogen atoms). You wouldn’t even need to trust to luck: You could actively divert the matter and antimatter in opposite directions when you make it.