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SYFY WIRE Bad Astronomy

Would you stand under a nuclear blast?

By Phil Plait

As a rational human, I'm aware of finding my emotions and prejudices conflicting quite often with my knowledge of science and reality. Being reasonable is relatively new to us apes, and a hundred million years of evolving reactionary emotions usually takes precedent.

So I find myself pretty conflicted about his video, which shows five men in July, 1957, standing around in the Nevada desert while a nuclear weapon is detonated above their heads.

[Note: the video says the detonation was 10,000 feet above their heads, but that is erroneous; it was more than 18,000 feet.]

This video comes from NPR via my own Discover Magazine. [Given what follows below, I'll note that the NPR article shows that these men were not adversely affected by the blast, and most lived to be old men. I strongly urge you to read that entire article, in fact. It's fascinating.]

When I watched the video, my feelings were curious. My first reaction was visceral: basically just "Aiieeeeee!"

But that was immediately followed by, "Well, the blast was low yield and about 18,000 feet up, so the odds of them getting hurt by it were pretty small."

The thing is, both thoughts are right! Here's why.

The blast was indeed a small one. It was not a fusion bomb (usually called a thermonuclear or H-bomb), but instead was a fission bomb, an A-bomb. These release far less energy when they explode, though it's nothing to be trifled with. This particular test was done using a 2 kiloton yield; in other words, it exploded with the energy of 2000 tons of TNT. For comparison, the only two atomic weapons used in wartime - by the US over Hiroshima and Nagasaki - had yields of about 13,000 and 21,000 tons of TNT. Hydrogen bombs have yields typically measured using megatons, or millions of tons of TNT.

So the explosion in this video was bigger than a usual conventional bomb, but not nearly as big as what we normally think of as a nuclear bomb. Right away we have to be careful how we think of this!

Second, the explosion was at a height of well over 5 kilometers (3 miles). As I pointed out in a recent BAFact, Earth's air is quite good at absorbing various types of electromagnetic radiation (a fancy name for "light"), including X-rays and gamma rays. The men under the blast probably received no direct dose of ionizing radiation in that form. It's possible the intense high-energy light from the bomb created secondary forms of radiation - high-speed electrons and so on - but again, the bomb yield was low, so all that air probably did a pretty good job stopping all that.

Third, what about fallout? This is radioactive material from the blast that falls from the sky. In an atomic (or an H) bomb, radioactive atoms are created and dispersed. In low altitude tests, the heat from the explosion can draw up dust from the ground, mix it with these materials, and create a radioactive cloud that can travel a long way. Raindrops can form, and the radioactive brew can literally fall out from the sky.

However, this was not a low-altitude test, so no dust got drawn up. And the radioactive material from the bomb would've blown sideways from the wind, away from the men underneath. Let's be clear: that sucks monumentally for anyone downwind, but these men were spared from that.

So really, in most ways, these men were pretty safe. In fact, the radiological effects on the men were measured to be extremely low. The worst effect from all this would've been potential eye damage from looking at the blast itself, which is very intense. Note that one of the men is wearing sunglasses and is looking up, while the other four are looking away. I suspect that one guy was, ironically, in the most danger from this. Sunglasses dim visible light, and your eyes respond by opening your pupil to let in more light. When the bomb went off, that meant more ultraviolet and infrared light entered his eye. This is why looking at the Sun is, in general, a bad idea.

So rationally, logically, and scientifically, this test was probably pretty safe for these five men (and the cameraman, too).

However, here's the thing: in those days, a lot of this wasn't really clear. This explosion was part of Operation Plumbbob, which was designed in part to test nuclear radiation and its effects from bombs. While a lot was known by this time - we'd been testing for over a decade at this point - any number of things could've gone wrong. In fact, the Starfish Prime explosion of 1962 (almost exactly five years after this test) showed that in spades, when the electromagnetic pulse from a hydrogen bomb detonated in space blew out traffic lights in Hawaii hundreds of kilometers away, shocking the scientists and engineers involved.

While the risk in this Plumbbob test was low, it wasn't zero. So both my reactions, I think, were right: the initial WTF, followed by Well, in fact, this is probably not nearly as bad as it looks.

And let me be clear: there were a lot of really bad after-effects from all that nuclear testing. A lot. Large numbers of people involved in testing developed radiological problems like cancer, and many died from these issues. I look back on those days and wonder what we were thinking. I understand the historical context, and also understand that through the lens of current understanding it's far more difficult to place ourselves in the shoes of those making decisions at the time.

So all in all, I'm glad I saw this video. It's terrifying, disturbing, enlightening, and like so many videos from the historic archives reveals us for who we are: conflicted, complicated, curious humans. We are emotional creatures, and to deny that is irrational. We need to understand that and embrace it to make sure that our decisions are based on reason and rationality, but also on our positive emotions which inform our morality. We shouldn't let our emotions rule our decision-making, nor should we deny them when trying to make the wise choice.

Related Posts:

- The 50th anniversary of Starfish Prime: the nuke that shook the world
- What the hell were we thinking?
- Repeat after me: cell phones donât cause brain cancer (and a followup post dealing with the same emotional vs logical issues)
- xkcd radiates

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