Imagine a brilliant would-be killer arranges the following scenario:

A coin will be flipped. If it’s heads, someone dear to you will die. If it’s tails, nothing happens. The bad guy — who is very bad indeed — will eagerly cheer for heads. But whatever the outcome, he’ll accept the coin’s verdict.

Let’s add that if it’s heads, the death will be 100 percent certain. But it will also be instant, painless, and without warning. And if it’s tails, your loved one will never know about any of this. Nor will you, or anyone. In other words, no PTSD. Nor even the faint, fleeting trauma of a rollercoaster ride.

And so, the coin is flipped, and… huzzah, it comes up tails! The bad guy is pissed. But rules are rules, so your loved one lives.

Years pass. Then one day, some ingenious cops discover all of this. Being geniuses, they’re also able to establish — with full certainty — that the bad guy will never do this again. Indeed, he poses absolutely no threat to society.

Given all this, was a crime committed? And should we lock the bastard up?

If your gut is screaming YES!!! I agree, as would almost anyone. That monster put your bestie, kid, or partner in horrible jeopardy. For fun!

Now, does the nature and severity of the crime change if the odds of death shift away from 50 percent?

I would say yes, if they move a lot. For instance, if the would-be victim squeaks past a 99 percent chance of death, prosecutors would tend to view it as attempted murder. But with a 1 percent chance of death, many would question whether the villain truly wished anyone harm and the charge might be something like reckless endangerment.

Intention and mindset matter more as the odds of a bad outcome plummet. Even imposing a one-in-ten-million chance of death feels criminal, if the bad guy’s praying like a Mega Millions ticket holder for the long shot. Whereas, if he deeply hopes that no one dies, this ceases to be a crime at some point. Particularly if there’s something in it for him other than a sadistic thrill.

That just sounds selfish — but we’ve all made similar tradeoffs.

This sounds strange, I know. But the perpetrator’s joy in the game is part of what makes it odious. So instead, suppose this guy would hate for anyone to die, or even stub a toe — but he desperately wants some Doritos. And to get his snack, he’s fine with making society bear a slim chance that someone croaks.

Now, that just sounds selfish — but we’ve all made similar tradeoffs. Like, a lot of them. For instance, if you’re American, your country racks up about 400 billion car rides per year, at the cost of 40,000 or so road deaths. So regardless of who’s at the wheel — be it you, Mom, or Lyft — a 10-million-to-one game of Russian Roulette kicks off whenever you cause a car to roll.

This shows us that when the odds of a calamity flirt with zero, we’ll serenely court outcomes as awful as death. Daily life would be impossible otherwise. No one likes to dwell on this reality. But it doesn’t violate our intuitions, because we realize that countless people die in the midst of truly mundane tasks.

Far more chilling and less intuitive is the fact that long-shot, all-or-nothing bets are now placed on a global level too — with humanity itself the de facto wager. Such a bet was first faced and considered in 1942. It was analyzed methodically. Then three years later, the bet was placed. The odds of a disaster were on the low side (one in 3 million, maximum). But the stakes were towering.

The gamblers were running the Manhattan Project. The risk wasn’t a nuclear war (yet), but that our atmosphere might burn up in a chain reaction triggered by their first atomic test. This prospect was first raised by Edward Teller, who later became the father of the hydrogen bomb. Robert Oppenheimer, who would soon lead the Los Alamos lab, called it a “terrible possibility”.

For his part, the head of the project’s theoretical unit “found that it was just incredibly unlikely.” But that sort of language is more comforting when, say, discussing a big softball game. So top people were convened to assess the danger. And confidence mostly reigned by the time of the test.

We now know this confidence wasn’t misplaced — so hats off to the team for getting it right! Although they were kind of right by fiat, since no one would be here to call them out if they’d blown it. It’s also worth noting that Enrico Fermi took bets on the burnt-sky scenario on the big day. Although he was joking, he scared the bejesus out of the enlisted men at the test site, none of whom could parse the reassuring math.

But not everyone put the odds at zero. The one-in-three-million estimate came from Arthur Compton, who oversaw the project’s plutonium production. And I’d say he was as smart as anyone there (Compton won the Nobel Prize for specifying light’s quantization from assumptions about the subatomic interactions of X-ray photons and their scattering angles — a sentence I don’t even understand).

As there wasn’t full consensus on the test’s utter safety, the team de facto accepted the small chance that they might incinerate the sky, and cancel the future. Could we say they had a moral basis for doing this?

To be clear, I’m asking about the decision to proceed with building, then later testing a nuclear device, and not the bomb’s subsequent wartime use. Hard as it is for us to separate the two, the scientists faced the risk of an atmospheric ignition in 1942. A working bomb was years off at the time, the war’s outcome was unknowable, and Germany was at least as menacing as Japan.

I’ll add that nuclear fission had first been discovered just a few years before — by German scientists. Allied intelligence also knew that Germany started its own atomic bomb project almost immediately thereafter. Subsequently, the Wehrmacht’s conquest of Norway put the world’s sole source of heavy water in Nazi hands. Though the German bomb project failed, there was no way to foretell this when Oppenheimer’s team assessed the atmospheric risk. Abandoning their project because of it would have therefore carried another risk: Hitler gaining a nuclear monopoly.

Some would contend the Los Alamos team was immoral to risk torching the sky despite all that. However, it would be very hard to argue that they were selfish for it. They each faced the same doom as everyone else if things went badly, and no extravagant rewards if things went well. In other words, gambling with humanity’s fate — or refraining from doing so — was a public service back then. And any upside from gambling successfully was a public good.

But how would you feel about all of this getting privatized? Both the act of gambling with humanity’s existence, and the payoff on the bet, if things work out?