Doc! I’m watching Monarch: Legacy of Monsters and in the second episode one of the characters says that scientists found radiation coming from an island in the Pacific, but not the kind that comes from a nuclear bomb. How do they know?
Good show! I’m not normally excited about another superhero movie or the next monster flick – but I’ve got to admit I enjoyed this show and I’m looking forward to watching the next season. Anyhow – I went back and rewatched the second episode and found the part you’re talking about. And, while this series is not what one might call scientifically rigorous, I think they’ve got a point. Let’s start with nuclear weapons.
When a uranium or plutonium atom splits it creates two major fission fragments, each of which is radioactive. These fission fragments are unequal in size and they have a distinct pattern of atomic masses if you study enough of them.
For U-235, for example, there are two peaks – the lower-mass fission products peak with a mass around 90 or so protons and neutrons and the high-mass peak is at around 130-135. This is why we see a lot of Sr-90, Tc-99, Cs-137, and I-131 – each of these is near one of the fission product yield peaks. This pattern is so distinct that scientists studying fallout from a nuclear weapon can tell whether it was fueled with U-235 or Pu-239…or a more exotic material such as U-233 or Np-237. An even more-detailed analysis can usually tell them the country that made the fuel or, in the case of a plutonium-fueled weapon (which is made in nuclear reactors), even the exact reactor in which the plutonium was produced. The US tested a number of nuclear weapons on Pacific islands, each of which was slightly different and would have had a different mix of fission products unique to the particular island and test. So that covers the bomb – now let’s look at the monster.
We all have traces of radioactivity within our bodies, primarily potassium in the form of K-40. So unless Godzilla (or Mothra or King Kong or Rodan or…) have a very strange biochemistry that doesn’t use potassium, the K-40 alone would be enough to distinguish monster from bomb. But even if the Big G ingested some fallout from a nuclear weapon it’s possible he’d have a different radiological signature than pure weapons fallout.
Consider – strontium mimics calcium in the body so it concentrates in bones and teeth; cesium circulates through the body and is rapidly excreted, iodine (in humans) collects in the thyroid gland, but elements such as ruthenium, technetium, promethium, and samarium aren’t very important. So even if Godzilla were ingesting fallout, and assuming his biochemistry is anything like ours, we’d expect to see isotopes of iodine and strontium – maybe some isotopes of uranium and plutonium (both of which, like strontium, can substitute for calcium in the bones), but we wouldn’t expect to see ruthenium, technetium, promethium, or samarium. In other words, if we study the radioactive emanations and see the full suite of fission products but no K-40 then we’re likely looking at bomb debris; if we’re seeing only a partial inventory plus nuclides of the biologically necessary elements then we might have bagged ourselves a monster. And here’s one advantage of studying a critter the size of an apartment building – there’s a LOT of mass, so we ought to get a pretty good spectrum of the biological nuclides. Yay!
But there’s an even more intriguing possibility – what if the monsters live in a different universe altogether? After all, later in the series they seem to dematerialize when they enter…whatever it is that gets them to their world…and then rematerialize upon arrival. Maybe they’re going to another part of our universe – but maybe they’re actually going to another universe where the laws of physics are a little different than they are here in our neck of the multiverse. In a case like that the laws of physics might not even let K-40 form or, if it does, it might give off a different gamma energy. So the natural radiation coming from Godzilla and his buddies might not be identifiable to scientists here – their instruments might simply respond “unknown” when trying to identify the various gamma peaks, or might identify something nonsensical. So this might another difference in the radiation given off by monsters compared to nuclear weapons.
That’s about as far as I can take this one. But hopefully it’ll help answer your question.