OK, I apologise in advance as this is a rather gruesome question.
We’re all seen the famous pictures of the shadows of people left on walls etc at Hiroshima and Nakasaki, this is usually accompanied by a caption stating that this is all that was left of the person and they were physically completely annihilated by the atom bomb.
I never really thought to question this until I read somewhere (possibly on this forum) that this is not actually true, the bodies of the victims were still present, just left a shadow on the wall behind them when they were removed for burial.
That’s about 7,200 degrees Fahrenheit, or roughly 5-6 times the temperature of a cremation.
There may be some bone or tooth fragments that remain, but any leftover ash would be blown away by the blast, and any flesh, organs, muscle or hair inside the fireball could fairly be described as vaporized.
I’m not necessarily doubting that the bodies were vaporized, but the mere fact that the bomb produced high temperatures doesn’t prove it. Cremation of a body takes 1-2 hours. The bomb flash may have created a temperature of 7200 F for only a few seconds. Of course there was a subsequent firestorm that burned the city, but whether the bomb itself vaporized bodies is a different question.
I think the OP might be confusing reality/things said about reality with a zillion TV/movie representations where “Hiroshima shadows” are left as the victims dramatically vaporize.
I don’t think the shadows (of unscorched paint or plaster) were created by vaporized individuals, but I’d bet they were scorched into unrecognizable form.
I’d also wager that some number of people directly under the explosion and reached by the hottest and fiercest part of the fireball were, for all practical purposes, vaporized.
There’s the famous small dome of iron girders on the building that was pretty much directly below ground zero in Hiroshima. It survived because (a) the blast was directly above, so there was no lateral blast force to knock down the concrete or block walls, and (b) supposedly the thin copper dome sheeting (you know, those old Victorian-type green domes) vaporized from the initial flash, so when the shock wave hit, it was pushing against thick solid iron girders not wide sheets that would catch a lot of the blast force.
If sheet copper can vaporize, odds are humans were somewhat disassembled corporally also.
That’s for a slow burn, low temp cremation. The higher temp, the faster the burn. At very high temps, like A-bombs and some fires, the heat is so intense that the water in the body flashes into steam. All burnable fuels in the body: fats, proteins, etc. then burn immediately. Bones shatter open and the marrow burns.
Funeral homes have no interest in creating such an outcome plus low temp is cheaper in terms of both construction and fuel use.
What a body does at one temp has little to do with what does at another.
Read Hersey’s Hiroshima, full of first hand accounts. Actual piles of ash were seen at the site of some of these shadows.
That doesn’t support the vaporization theory. The flash that produced the shadows would have arrived before a shock wave. Any pile of ash found near the shadows was not the result of a body being vaporized at the time the shadow was formed. It was either a body that smouldered there afterward, or it was ash that was blown there from elsewhere.
Note, however, that I’m not disputing the idea that some people were in fact vaporized. I’m just questioning this particular statement.
I doubt that the victims who cast the “shadows” were vaporized: It’s a calibration problem. If the radiation isn’t intense enough, then the body wouldn’t be completely vaporized, and if it’s too intense, then it’ll vaporize the body and then char the wall behind it anyway. Plus, to get shadows, it was necessary that even the charred portions of the wall remained standing, so you have to explain why the exposed wall wasn’t vaporized, too. Now, I’m sure you could vaporize a body with a nuke, but that would be at the distance where you’re leaving craters, not scorch marks.
I expect that piles of ash were found in all sorts of places. But I see no reason to suppose that the places where ashes were found were the same places where ash was produced.
Actually, piles of ash refutes the vaporization theory. Vaporization means, well, turned into vapor. There wouldn’t be any ash left if the bodies were literally vaporized. Even if we extend the meaning of “vaporization” to mean “instantly turned into ash rather than vapor”, it’s hard to imagine a scenario where the bomb flash reduced the body to ash, and then after the subsequent shockwave and winds arrived, the ash remained in a neat little pile.
Since it was an airburst at 1900 feet, and the fireball was roughly 750-800 feet in radius, the fireball itself never actually touched the ground.
But people directly below might have been exposed to instantaneous temperatures as high as 7200 F, as the thermal energy of a nuclear weapon is released VERY quickly. So the question is whether or not that would vaporize you, or just incinerate an outer layer, and cook you through.
Well yes and no, I’ve certainly seen those dramatisations but I’ve also seen pictures in proper history books with captions stating the same thing. This was why I was so surprised to read that it, possibly, didn’t actually happen that way.
Well metal isn’t quite the same thing as bone, I also recall reading that spheres of carbon were placed at ground-zero of thermonuclear tests and later recovered charred but intact some distance from the site. Those spheres were inside the nuclear fireball with temperatures of millions of degrees, the detonations over Hiroshima and Nagasaki were airbursts and the fireball never actually touched the ground.
I would think that the blast would rip you apart.
The overpressure at ground zero had to be hundreds of PSI (I don’t think I’ve ever seen an estimate). So, the combination of extreme temperature followed by an enormous blast wave would probably result in disintegration.
This page lists thermal and blast effects for various kiloton ratings at various distances from ground zero, and cites real-world photos. The first picture is of a building “near ground zero” in Hiroshima, with a claimed blast wave pressure of 19 psi. This would knock you around pretty good (probably to death), but I’m not sure it would physically destroy you. People who jump off of the Golden Gate bridge experience about 200 psi when they hit the water; they’re often (usually?) killed by the impact, but AFAIK they are not dismembered.
That (incredibly poorly presented) page seems to show that the maximum overpressure at Nagasaki was 52psi. So, I overestimated, but 52psi is probably enough to at least rip limbs off.
Hm, I doubt that. According to Randall Munroe here, the breaking strength of tendon is around 50-150 MPa. Even taking the lower value of 50 MPa, that’s over 7200 psi. This probably refers to actually pulling directly on a tendon, so it’s not really comparable to an external air pressure value. Still, it suggests that breaking a tendon is pretty darn hard. And as Machine Elf already noted, people hitting the water after jumping from the Golden Gate Bridge experience 200 psi of external pressure, but not only are they not dismembered, some actually survive.
Pretty sure the Golden Gate jumpers experience the worse scenario when compared to nuclear blast wave victims. Not only do they experience higher impact pressures, but the time scales involved are much longer. They hit the water about 90 MPH, whereas a nuclear blast wave near ground zero passes over them at several times the speed of sound (assume Mach 5, ~3800 MPH). For the jumper, the water pressure has more time to decelerate the initially impacting parts of the body before the other parts make contact with the water. Contrast this with the bomb victim, for whom the blast wave screams past him at about 50X that speed; no single body part experiences violent acceleration for very long before the blast wave arrives at other parts of the body, causing all body parts to accelerate at pretty much the same rate. Arms and legs may flail (see at 1:16 for test dummy near 500t conventional blast), but they should stay connected.
Complete layman chiming in, but wouldn’t the shadows be formed by a body that existed long enough to block the heat from reaching the wall behind, thereby producing a shadow? If the body vaporized instantly, what’s forming the shadow? (I know we’re talking about things happening at the speed of light, but vaporized implies that it was gone in the first instant. And is it the initial flash of light we’re talking about, or is there alsoa following heat wave that would be blocked by the body?)
I’m imagining the shadows were made by a body that certainly was burned and eventualy smoldered to nothing but ashes, but wasn’t immediately vaporized.
And where were these shadows found? Right at ground zero or miles away where the heat would have been extremely high but not ground zero intensity? If they were found somewhere distant, that would seem to support what I’m thinking here.
On the right track? Or am I missing something?
The heat was so instantaneous that the concrete was discolored behind many of the people who suddenly ceased to exist. Google it if you like, there’s many pictures.
ETA, I’ve heard stories from artillery people that 155mm arty does much the same thing if you’re close enough when it impacts.
As we are now in the times of knowing everything (at least we believe to), how about this BIG question, where they really vaporized?
Does it really matter, do we really have to know?
If yes, than just do it again and we will find out this time…