7 ms·
My observations during the explosion at Trinity (1945)
- hwc 10y agoWe did this calculation in a course I took in college. I've completely forgotten how it worked.
- Declanomous 10y agoAssuming the paper shifted perfectly laterally, I assume you'd just be measuring the difference in the volume of half a sphere ten miles in radius, and a sphere ten miles and 2.5 meters in radius. I think you could use the ideal gas law at that point to figure out the energy. I'm just guessing though.
- iaw 10y agoI think you're right. Ideal gas law wouldn't apply to the plasma sphere but knowing shockwave strength at some distance you can figure out how much energy was transferred to the atmosphere.
- adrianratnapala 10y agoI agree the calculation probably worked by measuring the kinectic energy of that half-shell by measuring its velocity*thickness directly using pieces of paper. But I wouldn't count the ideal gas law out (see http://physics.stackexchange.com/questions/43696/will-ideal-gas-law-apply-to-plasma http://physics.stackexchange.com/questions/43696/will-ideal-...). My guess is that the huge temperatures involved will work in favour of an ideal-gas approximation. Perhaps the more important thing is that things are happening on very short time-scales, far enough from equilibrium and temperature might not even be well defined.
- Declanomous 10y agoThat probably would work better. I tried doing the math and ended up with some really weird answers. Definitely not 10 kt.
- Kenji 10y agoI just love how practically minded these men were. Whatever they had available to them, they made it work somehow. If you want to read another account of the Manhattan Project / first nukes, I highly recommend the book "Surely you're joking, Mr. Feynman!" which contains a wealth of interesting and funny (and sometimes touching) trivia about the life of Feynman and how things went at Los Alamos.
- de_Selby 10y agoFermi was famous for this kind of thing, he could calculate the answer to a problem where it seemed like there wasn't enough information as if by magic.
- dekhn 10y agoNot calculate, estimate. You come up with a simple mathematical model- often just adding or multipling a few numbers together. It's not magic, he just had a good sense for including all the 0th and 1st order terms.
- antognini 10y agoIn one of my interstellar medium classes I remember learning about the physicist Geoffrey Taylor's estimate of the yield of the first atomic bomb. At the time, the energy of the atomic bomb was classified information, but photographs of the explosion like this one [1] had been published in newspapers and magazines. Crucially, this photograph was labelled with both the time after the explosion, and a scale bar. With just this information Taylor found it was fairly simple to calculate the energy of the explosion. He ended up publishing two papers about it [2] [3]. In astrophysics, his calculations are now used when modeling the effect of a supernova on the surrounding interstellar medium. [1]: https://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Trinity_Test_Fireball_25ms.jpg/250px-Trinity_Test_Fireball_25ms.jpg https://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Tr... [2]: http://rspa.royalsocietypublishing.org/content/201/1065/159 http://rspa.royalsocietypublishing.org/content/201/1065/159 [3]: http://rspa.royalsocietypublishing.org/content/201/1065/175 http://rspa.royalsocietypublishing.org/content/201/1065/175
- kkylin 10y agoThank you. I had known about Taylor's work from a course on scaling methods in continuum mechanics (it is also one of the introductory examples in Barenblatt's very nice book Scaling), but did not know that it has other applications.
- Jill_the_Pill 10y agoBarenblatt looks like something I need right now -- just put it on my library list for tomorrow. Thanks!
- semi-extrinsic 10y agoThose WW2 era photos are interesting, and I like the story about Taylor's analysis, but what really spooks me from early atomic bomb tests are the Rapatronic photos by Edgerton. He took high-speed photography to the ultimate limits, at exposure times of 10^-8 seconds, and the pictures are absolutely eerie looking. Some are like gaping skulls of pure energy, like this one: https://upload.wikimedia.org/wikipedia/commons/e/e9/Tumbler_Snapper_rope_tricks.jpg https://upload.wikimedia.org/wikipedia/commons/e/e9/Tumbler_... http://petapixel.com/2014/03/05/rapatronic-camera-atomic-blast-captured-11000000000th-second/ http://petapixel.com/2014/03/05/rapatronic-camera-atomic-bla...
- maverick_iceman 10y agoGreat resource on Fermi problems and related topics.[1] [1]https://mitpress.mit.edu/sites/default/files/titles/free_download/9780262526548_Art_of_Insight.pdf https://mitpress.mit.edu/sites/default/files/titles/free_dow...
- AstralStorm 10y agoExcellent page that is completely unreadable on mobile. Let us download a PDF at least.
- ChristianGeek 10y agoReadable on my iPhone 6s in landscape mode.
- coldcode 10y agoSeeing a black and white description of an explosion estimated at 10,000 tons of TNT is still mind-boggling. Even harder to believe that within a decade or so there were explosions of 100,000,000 tons of TNT. E=MC2 gets big in a hurry.
- Retric 10y agoNo single nuclear weapon detonation ever hit 100,000,000 tons of TNT. There are designs for weapons in that range, and single example at 1/2 that power. However, such designs are impractical as using the same material to carpet bomb an area is more effective. PS: Before the H-Bomb nuclear weapons where not actually cost effective per ton. Their 'advantage' over high explosives was portability and fear.
- astrodust 10y agoThe Tsar Bomba was supposed to be in this range, but the allegedly the designer of the weapon started to fear his own creation and decided to tamper with it and tone down the yield. https://en.wikipedia.org/wiki/Tsar_Bomba https://en.wikipedia.org/wiki/Tsar_Bomba
- maxxxxx 10y agoNo idea why you have been downvoted
- krylon 10y agoI kind of remember reading that somebody involved in the creation / testing of that bomb made a rough estimate of the area covered by the fallout and decided to ditch the U-238 damper on the second (third?) stage. Also, getting the plane dropping the bomb to a safe distance before the explosion was kind of an act as it was, if the bomb had gone off at twice the yield, it probably would have killed the crew. (All this is from rather fuzzy memory, though! If somebody has less fuzzy information, I'd be happy to stand corrected!)
- 10y ago
- tehchromic 10y agoOnce had a job working in the basement of a building in Los Alamos NM operating a digital scanner to digitize various documents from the lab archives. I encountered a few boxes of photos of various atomic tests - beautiful and spooky.
- pjmorris 10y agoObligatory reference to 'The Making of the Atomic Bomb', Rhodes. Terrific book on the people, physics, and politics behind 'The Bomb' and its use. Any recommendations on biographies of Fermi?
- rubidium 10y agoThe one by his wife Laura is very interesting: "Atoms in the Family: My Life with Enrico Fermi"
- tajen 10y agoIs there only one page? I'm on an iPad, there doesn't seem to be arrows for next/previous page.
- imglorp 10y agoYes, just one.
- meerita 10y agoImagine to witness a Tsar Bomba https://en.wikipedia.org/wiki/Tsar_Bomba https://en.wikipedia.org/wiki/Tsar_Bomba 64km tall mushroom head. About 8 kilometres (5.0 mi) in diameter, was prevented from touching the ground by the shock wave, but nearly reached the 10.5-kilometre (6.5 mi) altitude of the deploying Tu-95 bomber
- phatfish 10y agoWow, and the biggest threat we have today is immigration of (mostly) peaceful people. How quickly we forget.
- slackpad 10y agoTrinity site is an interesting place to visit - it's open to visitors twice a year. http://www.wsmr.army.mil/PAO/Trinity/Pages/Home.aspx http://www.wsmr.army.mil/PAO/Trinity/Pages/Home.aspx
- mgarfias 10y agoWhat I found most interesting about it, was the lack of interesting there. It could very easily be missed.
- craftandhustle 10y agoWhile reading this, I started wondering if there are any other 3rd party (civilian?) accounts of the event or if the geography / remoteness made it 'invisible' to everyone else? I have a funny visual in my head of a random farmer casually mentioning to his wife a 'weird glow in the horizon' on an otherwise regular Monday morning.
- chiefofgxbxl 10y agoDue to the blast in the desert, quartz and other minerals in the sand were melted to form Trinitite, a green glass. Would be interesting to hold this piece of history in a museum (according to Wikipedia, it's safe to handle). https://en.wikipedia.org/wiki/Trinitite https://en.wikipedia.org/wiki/Trinitite
- mgarfias 10y agoIt was all bulldozed into a small "building" on the site as it was too hot to leave around. There were lots of signs warning about it on the bunker when I visited in 2003/4.
- spirographer 10y agoIs there any way to determine exactly when this document was written? I've read accounts that indicate that it took some time (weeks, months, years?) before the metaphor of mushroom shaped cloud entered into the vocabulary used by witnesses of atomic weapons. Fermi's account would disprove that assertion if it were written immediately after the test at Trinity.