ELi5: Decades ago when countries were still testing nuclear bombs sometimes the scientists incorrectly predicted how large the explosions would be. How did they accurately calculate the actual size of the explosions after the fact?

Question

As the title says

In: 6

Answer 1

Well, what you do is stand miles from the explosion and drop small pieces of paper and watch how they move in the air when the blast wave hits.

No, seriously, this is what Enrico Fermi did at the Trinity Test, the detonation of the world’s first nuclear bomb (the Gadget). He calculated it to be at least 10kt whereas the official results were 18kt so not bad for just dropping pieces of paper in the air.

There were a lot of ways they’d officially measure how powerful the blast was. One was by looking at how much radiation was given off by measuring the fallout. This only works if you get fallout, obviously. Another was how powerful the blast wave was. How bright the fireball was. How much the ground shakes (for, you know, explosions on or under the ground).

However, using each for the same explosion can give different results so…………………….