Timeline for What would a sufficiently dense sphere of uranium do first: blow up, or form a black hole?
Current License: CC BY-SA 3.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jun 25, 2013 at 22:46 | comment | added | Deer Hunter | This is a tough question to answer without numerical modelling. Suggest editing out "calling into existence". If you don't specify the real size of the beast, it is impossible to say whether the process of explosive disassembly throws the material far enough to stop the process of black hole creation. It's interesting to consider the ramifications of possible inhomogeneity of neutron flux in the beast... | |
| Jun 25, 2013 at 22:44 | vote | accept | Zev Chonoles | ||
| Jun 25, 2013 at 22:21 | comment | added | Zev Chonoles | @user1504: Do you mean something like "would the uranium scatter fast enough that it would be impossible for it to form a black hole?" | |
| Jun 25, 2013 at 22:09 | comment | added | user1504 | -1: What you've got here -- 'calling something into existence' -- doesn't seem like a physically acceptable fiction to me. Try phrasing this as a scattering experiment. | |
| Jun 25, 2013 at 21:01 | comment | added | Zev Chonoles | I am simply asking how the currently-understood laws of physics would play out, given an initial configuration of a large sphere of fissile material. How the initial configuration came to be, or even whether we think it is possible, seems irrelevant. This question seems to have gotten a positive response for example. But I accept the possibility that this question is not appropriate here; is that what you are arguing? | |
| Jun 25, 2013 at 20:50 | comment | added | dmckee --- ex-moderator kitten | Which either (1) violates the conservation of energy or (2) requires a pre-existing configuration of some kind of energy satisfying the requirement to be a black hole, so it is already is a black hole. | |
| Jun 25, 2013 at 20:39 | comment | added | Zev Chonoles | @dmckee: Well, that is why I asked that the sphere be "called into existence", in a completely non-realistic way. But in comparision, I have certainly heard famous thought experiments about, for example, the Sun instantaneously disappearing - this seems like an acceptable fiction to consider. I completely agree, that it seems realistically impossible to get enough fissile material together in any way without it blowing up first. | |
| Jun 25, 2013 at 20:31 | comment | added | dmckee --- ex-moderator kitten | And you're going to get that much uranium together without it first exploding, how exactly? Whatever initial configuration you envision it will have to more through a phase where you begin to increase the density. Now it is not as easy as saying "as soon as 65 kg have the natural density it goes off" because criticality is notoriously dependent of the details of geometry, but you have to keep compacting it over orders of magnitude, so your done for long before you get any kind of collapse. | |
| Jun 25, 2013 at 20:22 | comment | added | Zev Chonoles | @dmckee: But it didn't create conditions comparable to those where the uranium might have formed a black hole. I feel my question is fairly clear about specifying that I am imagining a situation where gravitational collapse is a relevant effect, in addition to nuclear fission. | |
| Jun 25, 2013 at 20:19 | comment | added | dmckee --- ex-moderator kitten | The bomb used on Hiroshima (called "Little Boy") was a critical Uranium mass assembly device. It used on order of 64 kg of 80% U-235, so in the most naive interpretation this question is a no-brainer. | |
| Jun 25, 2013 at 19:25 | answer | added | John Rennie | timeline score: 3 | |
| Jun 25, 2013 at 17:53 | history | asked | Zev Chonoles | CC BY-SA 3.0 |