# How much radiation is too much?

Summary:
How many equivalent megatons of TNT from a nuclear device would blanket the world in enough radiation to destroy all life?
I've had this question rattling around in my head for some time now, but I think it'd be easier asking it here than reading several books to gather sufficient information to answer it: I've heard that, in general, the detonation of enough nuclear weapons on a short enough time scale will cause the atmosphere to become so radioactive that all exposed life dies.

My question is this: Is there some strict equivalence of megatons of TNT of nuclear device detonation before the world will definitely be blanketed in enough radiation for this to occur?

vsvats72

PeroK
Homework Helper
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2020 Award
I hope you're not an international terrorist?

davenn, david2, pinball1970 and 1 other person
sophiecentaur
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There is a fair amount of information about the results of nuclear explosions. There are measurable disbenefits from even low levels of exposure. But I’d imagine ‘just enough to kill everybody would be hard to estimate. All the nuclear powers will certainly have calculated ‘how much we could get away with?’. That’s a chilling thought.

There is a fair amount of information about the results of nuclear explosions. There are measurable disbenefits from even low levels of exposure. But I’d imagine ‘just enough to kill everybody would be hard to estimate. All the nuclear powers will certainly have calculated ‘how much we could get away with?’. That’s a chilling thought.

Yeah. A viability analysis of how many people have/could survive and/or how long one would need to wait in a fallout shelter before re-emerging given the types and amounts of radiation emitted per equivalent megaton of TNT per type of nuclear warhead certainly interests those who want to engineer human survival post nuclear exchange.

russ_watters
sophiecentaur
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“Survival”? Wow, and they’re in charge of our fate.

anorlunda
Staff Emeritus
ARS involves a total dose of greater than 0.7 Gy (70 rad), that generally occurs from a source outside the body, delivered within a few minutes.

Aside from that, it becomes a matter of definition. Do people in Miami, FL (low radiation) live longer than those in Denver, CO (high radiation)? It seems like the answer is either no, or that factors other than ambient radiation dominate life expectancy.

https://www.rwjf.org/en/library/interactives/whereyouliveaffectshowlongyoulive.html

Florida 78.9 years

pinball1970
Staff Emeritus
Megatons and sieverts are not commensurate units. While they are not completely unrelated, one might as well ask how many pounds of bombs one needs.

Megatons and sieverts are not commensurate units. While they are not completely unrelated, one might as well ask how many pounds of bombs one needs.

That doesn't sound intuitive to me. I hypothesize that both fundamental mathematics and experimental measurements of bombs of the same type (say, uranium warheads) and payload would have enough empirical data to state how much radiation of some type (say, Gamma) the bomb itself emitted, and thus by simple algebra, the gamma radiation emitted per megaton of payload.

This isn't to say that geometrically increasing the payload wouldn't exponentially increase the radiation type per megaton of payload, but it would be a helpful system to use if you knew what type and payload of nuclear warhead had detonated - Alongside other pertinent information, like average atmospheric dissipation of radiation type and average minimum fatal dose of different radiation type.

pinball1970
Gold Member
Summary:: How many equivalent megatons of TNT from a nuclear device would blanket the world in enough radiation to destroy all life?

I've had this question rattling around in my head for some time now, but I think it'd be easier asking it here than reading several books to gather sufficient information to answer it: I've heard that, in general, the detonation of enough nuclear weapons on a short enough time scale will cause the atmosphere to become so radioactive that all exposed life dies.

My question is this: Is there some strict equivalence of megatons of TNT of nuclear device detonation before the world will definitely be blanketed in enough radiation for this to occur?
I would read the details of this disaster in 1986.
https://en.wikipedia.org/wiki/Chernobyl_disaster
The clean up will continue for generations.
This was a plant not a bomb and was obviously an unintentional release of radiation but the short term and long term effects should give you some ideas of the effects any living thing within range.
Some of the levels received were well documented.
@anorlunda put a link also, this will be in there.

pinball1970
Gold Member
but it would be a helpful system to use if you knew what type and payload of nuclear warhead had detonated - Alongside other pertinent information, like average atmospheric dissipation of radiation type and average minimum fatal dose of different radiation type.

Useful if you want to wipe out life on the planet yes. Are you writing a book? There is a section for that.

Last edited:
Staff Emeritus
That doesn't sound intuitive to me.

Well, then do the calculation yourself.

You are not interested in radiation so much as radioactivity. Two bombs next to each other have a different impact than two in different places. Just to pick one example.

I just read the Wiki article. Apparently a frontier theorist believed simply surrounding an H bomb with hundreds of tons of Cobalt and detonating it would create/disperse enough Cobalt-60 to make much of the earth too radioactive to sustain life.

I just read the Wiki article. Apparently a frontier theorist believed simply surrounding an H bomb with hundreds of tons of Cobalt and detonating it would create/disperse enough Cobalt-60 to make much of the earth too radioactive to sustain life.
Not an H-bomb, a few hundred megatons of H-bomb

CommissarCold
Radiation per se, isn't the issue. Take the solar for the surface of the Earth, (e.g. google it). Then take the area of the Earth. You find the amount of radiation the Earth receives from the Sun over the course of the day by multiplying the power received by 86400 seconds. Then you convert for example from Joules to megatons, (there actually is such a conversion (google it)). You will find the Earth receives 3.6 million megatons of radiation from the Sun per day. I am sure this is more than the explosive power in all the Earth's arsenals in the course of a day if exploded all in in one day.

Instead we can turn your question around. If the Sun were to quit shining, how long could we sustain life on Earth if we had all the energy available in our explosive arsenals? Gives you a good idea of how important the Sun is.

I can't help but think of the movie from 1959 "On The Beach" starring Gregory Peck, Ava Gardner and Fred Astaire. If you haven't seen it then please look it up.

CommissarCold, russ_watters and sophiecentaur
sophiecentaur
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2020 Award
I can't help but think of the movie from 1959 "On The Beach" starring Gregory Peck, Ava Gardner and Fred Astaire. If you haven't seen it then please look it up.
I walked out of the cinema more depressed than after any film before or since.
As an Engineer, though, I was disappointed in the source of those radio signals. Too Hollywood, I thought.

I can't help but think of the movie from 1959 "On The Beach" starring Gregory Peck, Ava Gardner and Fred Astaire. If you haven't seen it then please look it up.

Excellent movie. O.K., the radio signal is a bit flimsy, but the movie gives a dire warning in a time when leaders still thought a nuclear war could be won.

sophiecentaur
"On the Beach" is a very powerful movie and the book is even more dramatic. Sobering. Scary. Any way I can describe it cannot do justice to it. Not a good movie to watch or book to read if depressed.

sophiecentaur