# Light battery **URL:** \ **Category:** Factual Questions\ **Created:** [August 2, 2004, 8:46pm UTC](https://boards.straightdope.com/t/light-battery/258021 "2004-08-02T20:46:22Z")\ **Posts on this page:** 8\ **Page:** 2
**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:** [August 3, 2004, 6:27pm UTC](https://boards.straightdope.com/t/light-battery/258021/21 "2004-08-03T18:27:11Z")
Anywhere in the Universe which is not at absolute zero (which is to say, anywhere in the Universe, since of course [the Universe itself has a temperature](http://www.straightdope.com/mailbag/mspacetemp.html)) you have photons flying around. If you have an object at thermal equilibrium with its environment (that is, it’s at the same temperature), it’ll absorb photons and emit photons, and the amount of photons it absorbs will be about the same as the amount it emits. The object will neither gain nor lose energy. If it’s cooler than its surroundings, it’ll still absorb and emit light, but it’ll absorb more than it emits, and you’ll have a net energy flow from the hotter environment to the cooler object. But now suppose you have this one-way box. It’ll absorb more photons than it emits, no matter what its temperature or the temperature of its environment. Put it anywhere at all, and it’ll soak up energy. Since its environment is losing energy, it’s getting cooler. When your box is full enough, you open it up and use that energy. You’re getting useful work out of a decrease in temperature of your environment, which is a thermodynamic impossibility. OK, so we don’t have a magic one-way material, then. Back to the really bright light source and the quickly-closed door, then. Is there any theoretical limit to how much light you can cram in there? Not until you get to a black hole (which would take a heck of a lot of light, let me tell you). Photons are a type of particle called a boson, which means that their spin is an integer (a very interesting piece of information, to a physicist). But all you need to know about bosons is that, unlike fermions (protons, neutrons, electrons, etc), you can have any number of bosons all sharing the same quantum state together. Which means that, unlike fermions, you can have as many of them in the same place at the same time as you like. It’s OK if they overlap, or even overlap completely. ---
**Author:** ![InvidiousCourgette](https://avatars.discourse-cdn.com/v4/letter/i/e47c2d/32.png) [@InvidiousCourgette](https://boards.straightdope.com/u/InvidiousCourgette)\ **Post date:** [August 3, 2004, 6:50pm UTC](https://boards.straightdope.com/t/light-battery/258021/22 "2004-08-03T18:50:45Z")
I like this thread 🙂 > [@Chronos](#): > > But now suppose you have this one-way box. It’ll absorb more photons than it emits, no matter what its temperature or the temperature of its environment. Put it anywhere at all, and it’ll soak up energy. Since its environment is losing energy, it’s getting cooler. When your box is full enough, you open it up and use that energy. You’re getting useful work out of a decrease in temperature of your environment, which is a thermodynamic impossibility. What if our (increasingly difficult to build) box did not have a temperature? Say the box contains zero atoms. Would the 2nd law still cause a problem for out light battery manufacturer? ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [August 3, 2004, 7:28pm UTC](https://boards.straightdope.com/t/light-battery/258021/23 "2004-08-03T19:28:34Z")
Site covering allegation made in earlier post. ``` The MSNBC article: Speed of light site No. 4 ``` Clarifying Einstein’s rules of the road Physicists clear up misconceptions about ‘faster than light’ transmission By Alan Boyle MSNBC July 19, 2000 — Can anything break the cosmic speed limit of 186,000 miles per second? For weeks, scientific circles have been buzzing about an experiment that pulsed light through a special chamber so fast that it left the apparatus before it fully entered it. Now the research has been released at last, and the experimenters say their findings contradict no laws of physics — just the misconceptions people have about them. Refer: \<[http://www.msnbc.com/news/435007.asp?cp1=1](http://www.msnbc.com/news/435007.asp?cp1=1)\> ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 3, 2004, 8:14pm UTC](https://boards.straightdope.com/t/light-battery/258021/24 "2004-08-03T20:14:25Z")
When you build this impossible object, it will not only be a power source, but an effective refrigeration unit too. ---
**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:** [August 3, 2004, 9:35pm UTC](https://boards.straightdope.com/t/light-battery/258021/25 "2004-08-03T21:35:15Z")
> [@](#): > > What if our (increasingly difficult to build) box did not have a temperature? Say the box contains zero atoms. It would also have to contain zero photons, which would rather defeat the purpose. A temperature can be associated with photons as well as with atoms. For that matter, black holes have a temperature, too, despite having apparently no structure at all. ---
**Author:** ![threemae](https://avatars.discourse-cdn.com/v4/letter/t/5f9b8f/32.png) [@threemae](https://boards.straightdope.com/u/threemae)\ **Post date:** [August 3, 2004, 9:50pm UTC](https://boards.straightdope.com/t/light-battery/258021/26 "2004-08-03T21:50:32Z")
> [@audilover](#): > > No one said anyting about degrees. The reference was to energy flux, which is not a measure of temperature. Watts per square meter does not equal degrees. > > I was mistaken, BTW. That’s the energy flux above the atmosphere. Also, the number is closer to 1400 W/m^2, anyway. ([Cite, page 2](http://www.science.gmu.edu/~hgeller/astrobiology/AbSpaceTrav.doc)) > > But the point remains. That’s how much power the Sun delivers per unit area at the Earth’s orbital distance…not how hot the Sun makes the Earth’s surface. I know, I know, watts not degrees. I saw this as soon as I posted, but I decided to just let it go, I thought people would assume that I read and meant watts. But still… no way. Really, 750 W of power over a single meter squared from the sun? I guess that the value seemed really high to me. I mean, what does a microwave put out, 1500 Watts? And it will burn a chicken wing to a crisp in just a few minutes… Now filet that chicken wing out into 1 mm thick sections and spread it over a square meter… You get the idea. I’m not now, but I was shocked to find out that the value was so high. ---
**Author:** ![InvidiousCourgette](https://avatars.discourse-cdn.com/v4/letter/i/e47c2d/32.png) [@InvidiousCourgette](https://boards.straightdope.com/u/InvidiousCourgette)\ **Post date:** [August 4, 2004, 11:17am UTC](https://boards.straightdope.com/t/light-battery/258021/27 "2004-08-04T11:17:12Z")
Bahhh. Cheating, dirty, rotten Laws of Thermodynamics. Does anyone need a crate load of mirror sunglasses? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 4, 2004, 11:26am UTC](https://boards.straightdope.com/t/light-battery/258021/28 "2004-08-04T11:26:38Z")
> [@threemae](#): > > I know, I know, watts not degrees. I saw this as soon as I posted, but I decided to just let it go, I thought people would assume that I read and meant watts. > > But still… no way. Really, 750 W of power over a single meter squared from the sun? I guess that the value seemed really high to me. I mean, what does a microwave put out, 1500 Watts? And it will burn a chicken wing to a crisp in just a few minutes… Now filet that chicken wing out into 1 mm thick sections and spread it over a square meter… You get the idea. > > I’m not now, but I was shocked to find out that the value was so high. - or make a 1 metre square parabolic reflector and place your chicken wing at the focus - it catches fire rather quickly. [Previous page](https://boards.straightdope.com/t/light-battery/258021.md?page=1)