# How much of the fissile material in an atom bomb is converted to energy? **URL:** \ **Category:** Factual Questions\ **Created:** [October 31, 2008, 2:53pm UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431 "2008-10-31T14:53:51Z")\ **Posts on this page:** 9\ **Page:** 2
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [October 31, 2008, 6:30pm UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431/21 "2008-10-31T18:30:44Z")
> [@NaturalBlondChap](#): > > The exact split depends on the energy of the incident neutrons and the parent atoms, but generally speaking the fission products will lie in two groups , one with atomic mass in the 90-100 range and the other group in the 110-140 range Thanks, that’s more in line with what I remembered. What is the appropriate term if decay isn’t it? Just split? As in “in an atom bomb Uranium x into this and that” ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [October 31, 2008, 6:39pm UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431/22 "2008-10-31T18:39:30Z")
> [@Sapo](#): > > Thanks, that’s more in line with what I remembered. > > What is the appropriate term if decay isn’t it? Just split? > As in “in an atom bomb Uranium x into this and that” Fissions. ---
**Author:** ![Precambrianmollusc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/precambrianmollusc/32/63_2.png) [@Precambrianmollusc](https://boards.straightdope.com/u/Precambrianmollusc)\ **Post date:** [October 31, 2008, 6:47pm UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431/23 "2008-10-31T18:47:13Z")
> [@Sapo](#): > > Thanks, that’s more in line with what I remembered. > > What is the appropriate term if decay isn’t it? Just split? > As in “in an atom bomb Uranium x into this and that” Well I used to be a physicist, but a terribly bad one, so don’t trust me too much, but decay is generally accepted to be a small change in atomic mass through one of the common forms of decay (alpha, beta (in all its forms) and gamma) When it is undergoing fission , which is to say splitting into two substantial parts that are not covered by the above decay mechanisms, I beleive it would be correct, if a little clumsy,to say the uranium atom fissioned into x and y, but most of the time people go with ‘split’. ---
**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:** [October 31, 2008, 6:49pm UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431/24 "2008-10-31T18:49:40Z")
> [@](#): > > 600mg of Atoms may have been split, but no known process converts matter to energy with 100% efficiency. Addendum: There are at least two known processes which can convert matter to energy with 100% efficiency, and one more which can achieve 50% efficiency. All three of them, of course, are far beyond our level of technology, and only the third one has ever been observed in nature. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [October 31, 2008, 6:51pm UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431/25 "2008-10-31T18:51:55Z")
Well, my apologies for spreading mis-info with post #14. 🙂 For some reason, I failed to consider that the article(s) was discussing natural decay vice chain reaction fission. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [October 31, 2008, 7:01pm UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431/26 "2008-10-31T19:01:41Z")
> [@Chronos](#): > > Addendum: There are at least two known processes which can convert matter to energy with 100% efficiency, and one more which can achieve 50% efficiency. All three of them, of course, are far beyond our level of technology, and only the third one has ever been observed in nature. Isn’t there a rule against teasing? Tell us what they are. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [October 31, 2008, 7:05pm UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431/27 "2008-10-31T19:05:26Z")
> [@Sapo](#): > > Isn’t there a rule against teasing? Tell us what they are. I also would like to know what the other way of converting 100% to energy is. One of them is fairly obvious. As to the 50% one, I’m guessing it’s either gravity waves of black holes encircling each other or fusion/x-rays from matter falling into a black hole. ---
**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:** [October 31, 2008, 9:47pm UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431/28 "2008-10-31T21:47:15Z")
Sorry, I guess I should follow up on that. The first way is to feed the matter into a black hole, and wait for it to come back out as Hawking radiation. Hawking radiation is mostly massless particles (what most folks would consider “energy”), and has no preference for matter vs. antimatter (no matter what was fed in), so anything that wasn’t already massless, you could annihilate to produce energy. Unfortunately, Hawking radiation depends on the size of the black hole, and for any black hole known to exist in the Universe, it’s pathetically weak. You’d need a very small hole to make this practical. The second method is proton decay: Most current theories predict that the proton will eventually, after a very long time, decay, producing a positron and a bunch of other stuff. Again, anything that isn’t already massless could be annihilated with other reaction products to produce stuff that is. The problem here is that proton decay is phenomenally slow, and would ordinarily take many times the lifespan of the Universe. On the other hand, the same theories which predict it also predict that it should occur much, much faster (fast enough to be practical) in the presence of a magnetic monopole. So the problem is just one of finding or making a monopole. The third process is to drop things into a black hole, and extract the gravitational potential energy as you do so. Some inevitably gets into the black hole, but you can in principle get an output of up to half of the mass you started dropping in. You can use any size black hole whatsoever for this one. This is basically the process which powers quasars, though there it’s uncontrolled and a lot less efficient. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [November 1, 2008, 8:09am UTC](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431/29 "2008-11-01T08:09:04Z")
What about antimatter ? That’s a 100% conversion process, and it’s one we can perform even with our technology on a tiny scale. [Previous page](https://boards.straightdope.com/t/how-much-of-the-fissile-material-in-an-atom-bomb-is-converted-to-energy/470431.md?page=1)