I saw a post on here showing the ‘shadow’ of a boy standing near the Hiroshima & Nagasaki bomb explosion, it’s not actually his shadow but just the spot that didn’t get ‘bleached’ by the damage of the explosion. I read that he was vaporized in quite a lot of comments on this case but one comment explained that the boy wasn’t actually vaporized, but how did he actually die? Where is his corpse or what’s left of it? How is the damage of atomic bombs different than ‘normal’ bombs used in wars?
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When a nuclear device detonates, the first thing that happens is a massive release of radiation – gamma rays and neutrons. The vast majority of these are absorbed by the air surrounding the device, heating the air up to incandescent temperatures. Some of that radiation may travel much further, and irradiate objects on the ground. The heat of the air will also re-emit radiation as light at longer frequencies, ranging from UV to Infrared.
So for the boy on the ground, and the ground around him, the first thing to hit will be gamma radiation, and lower frequencies. Depending on how close he was to ground zero, this may have been a lethal dose of radiation, but it would not kill him instantly. Following the gamma radiation comes UV and IR radiation. The gamma, UV and IR radiation are what bleached the ground, and imprinted his shadow on the ground. The UV would cause sunburn, and the IR physical burns. Again, he may have been close enough to be vapourised, but I suspect not.
As the atmosphere heats up, it expands. This massive expansion of superheated air is the source of the shockwave that follows the initial radiation-based flash. Under the detonation point, people and buildings are pounded flat. Further out, the shockwave is pushing away with tornado-strength winds, knocking buildings over and throwing people into rubble and surviving structures. The wind feeds fires started by the intense radiation. This is most probably the fate of the boy – irradiated, burned and thrown by the shockwave. There may well have been no identifiable remains, or the body may have burned in the resulting fires.
>How is the damage of atomic bombs different than ‘normal’ bombs used in wars?
Conventional explosive bombs generate a shockwave and shrapnel by detonating a chemical explosive. This generates a ball of hot gases that propel the metal casing and materials round the bomb over a wide area, causing damage. There is no burst of radiation, and so the heat generated is limited to that of the explosive. The shockwave is very similar, but does not have the scale of destruction that can be achieved in a nuclear device. The Hiroshima bomb delivered an explosion similar to about fifteen thousand tons of TNT explosive, in a device that was only 64 kilograms. Based on the largest WWII bomb, it would have taken one thousand five hundred Lancaster bombers to deliver 10 ton “Grand Slam” bombs all at the same time. That number of planes and bombs did not exist at the time.
the light is so bright that it bleached everything, but when there was something in the way, the light couldnt get to it and that created a “shadow”. its like when you leave furniture out on the sun for a long time or even your hair – the colour fades after a while from the exposure to the light. the extreme heat is what killed the people standing the closest. its like when you forget youre boiling water on the stove and the water just disappears. but it’s obviously much much faster. also the extreme pressure, like the submersible with the millionaires. there are no corpses, just the shadows. they died in an instant, before their brain could even register what happened, so they suffered way less than the people who were further away.
the difference is that atomic bombs are way more powerful. the explosion creates a massive fire ball that’s as hot as the sun. it also creates massive shock waves. atomic bombs explode in the air and not when they hit the ground, which creates two shock waves. the shock wave is so strong the airplane flying away after dropping the bomb could feel it even though they were already kilometres away. normal bombs leaves corpses, but atomic bombs make people disappear. it sounds like a horrible way to die, but the ones who were near enough to disappear were luckier than the ones further away. the worst about normal bombs is the explosion, but with atomic bombs it’s what comes afterwards. the heat burns your skin, the pressure makes your eyes explode… if you’re further away, the heat makes fire tornadoes and the pressure destroys all the houses near. and then comes the biggest difference between those two – the radiation. i’m sure you know what that does so i won’t go into detail. what normal bombs do is horrible, but what happens in an atomic bomb explosion is absolute hell
Nuclear bombs have different effects that extend to different radii. What you get hit with depends on the bomb and height of detonation.
Fireball: This is vaporized, you instantly cease to exist. Bombs like in Hiroshima are usually air burst, so the fireball doesn’t touch the ground and nobody is vaporized. The fireball radius is relatively small compared to the other effects, and detonating it low enough to use the fireball means attenuating the other effects. So air burst is preferred unless it’s a very hard target.
After this, all effects taper off at a distance, but radii are established for a certain known degree of effect.
Thermal radiation: This is an extreme heat that lasts only milliseconds, and it’s only line of sight from the explosion. Everything gets cooked, but only to a shallow depth. People get instant burns, fence posts are charred only on the facing side, and stone surfaces are altered. This is your bleaching, and you see shadows where the radiation is blocked. Granite even gets rough because the smooth surface crystals are melted and refreeze.
Absorption of the radiation even depends on color. A white paper sign hanging far from the blast was unaffected, except that the letters in black were burned out.
Ionizing radiation: Instant lethal dose for 50% of those exposed, dead within a week (although most will still probably die later).
Blast: Extreme over pressure enough to instantly crush a person and wipe out concrete buildings.
Edit: Oh yes, the answer on how he died. He got hit with the thermal radiation instantly upon detonation, and then the blast took him out some milliseconds later. He probably didn’t even know he was burned.
My late father was involved in the British H-Bomb trials in the late 50s in the Pacific and personally witnessed two of the “Grapple” tests including Grapple Y which was equivalent to 3 Megatons of TNT. As is correctly shown in the Oppenheimer movie, my Dad was instructed to lay face down on the ground (actually the deck of a Royal Navy ship) away from the explosion, and place the balls of his hands over his eyes. He told me he still saw the flash. They were 20 miles from “ground zero” and over the horizon.
Kurzgesagt did an [excellent video about the effects and aftermath of a nuclear weapon used on a city](https://www.youtube.com/watch?v=5iPH-br_eJQ) in a digestible ELI5 format. I recommend watching it if this topic is interesting to you!
To actually be rendered into vapor you’d have to be very, very close to the fireball. The bombs at Hiroshima and Nagasaki were detonated too high for that. (The exact distance you would need to be would depend on the size of the nuclear bomb detonated. The bombs at Hiroshima and Nagasaki were detonated about 2,000 feet in the air, to spread their more “medium” damage out to a larger area.)
The people who died there in the immediate (several weeks) aftermath died because they were crushed (by buildings or objects or trees that were knocked over or collapse), knocked into things by the blast wave, burned by exposure to the radiant thermal energy (the immediate heat), burned to death by the subsequent fires that spread after the detonation (many were alive but trapped under buildings, and then the buildings burned), drowned in the boiling-hot rivers that they sought refuge in from the fire, died from injuries sustained through things like windows shattering in their faces, and/or received a high radiation dose (depends on how close they were to ground zero, whether they were inside a building or not, etc.) that could increase to mortality of any other injuries (like burns) or kill them outright (acute radiation syndrome) if it was high-enough.
There were also people at both who would later die of fatal cancers caused by their radiation exposure. This is fewer than most people tend to guess, but still several thousand people.
The reason the corpses are missing in most of the photographs of the damage is because the photographs were taken in September or October 1945 for the most part. The first thing the Japanese Army did when it sent relief to Hiroshima and Nagasaki was dispose of corpses, often by cremation. This was for both sanitary and religious reasons. But it means that most of the photos we have of the damage are “corpse-less,” which has fueled a lot of misunderstandings (like the idea that people were just vaporized, as opposed to dying very painfully and then being cremated).
The difference between atomic bombs and conventional bombs is that atomic bombs are as a rule much, much more powerful than conventional bombs. Thousands or millions of times more powerful, depending on the bombs you are comparing. They also have radiation as an effect, both as an immediate one and as a delayed one (fallout, which was not a big issue at Hiroshima and Nagasaki because of the size of the bombs and the altitude they were detonated, but would be in any large-scale nuclear war). They also deliver all of their energy all at once, which can make them much more deadly than even an equivalent amount of conventional explosives being dropped over time.
Its like putting a sticker on your arm and getting a suntan.
Peel off the sticker and you have a “shadow” of the sticker.
That’s what happened here. The whole city got an instant suntan from the UV light from the bomb, it’s just that the person blocked it in the instant the bomb went off. It was the world’s worst camera flash.
There’s other pictures of leaves and pipes casting the same shadow. There must be a focus effect in play, only things on the ground or close too it would leave a shadow, the light would bounce around behind anything else and suntan the shadow away.
ELI5: The nuke threw a bucket of “suntan paint” everywhere. Its not that the person left a shadow, it’s that everything in the city got a suntan and the shadow is actually the original color of the city before it got irradiated.
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