Possible to calculate the strength of a nuclear explosion from a photo?

[CPW]

TL;DR Summary

I read that a student in a physics class was told that one can calculate the strength of a nuclear explosion from the photo of a mushroom cloud from the explosion. I assume the dimensions of the cloud can be determined from the photo.

But what are the details of this calculation?

Details of this calculation from the photo?

 

[mathman]

To start with you need to know how far away was the camera.

 

[phyzguy]

I think you're probably referring to G.I. Taylor's calculation of the yield of the Trinity nuclear test using dimensional analysis. Here is a link to that calculation. You need to know the radius of the fireball at a particular time, so you either need a movie, or you need a single still photo with the knowledge of how long after the detonation it was taken.

 

[anorlunda]

My favorite was the anecdote about Enrico Fermi at the Trinity test. He estimated the yield by dropping a scrap of paper at the right moment and noting the horizontal displacement before hitting the ground.

Source: I'm not sure but perhaps "The Making of the Atomic Bomb"

 

[CPW]

I just reviewed the link to the GI Taylor calculation (link above from phyzguy), and I understand the dimensional analysis. I appreciate the approximations made, and so I think that the answer is in the correct order of magnitude.

In fact, I find this calculation very interesting and a useful demonstration of the power of dimensional analysis and basic physics.

Related to this calculation is the claim that we can calculate from seismic readings (modern military seismic network, leftover from the cold war) the strength of an underground nuclear weapon test far away. Like the GI Taylor calculation this is very interesting, but is certainly a more involved calculation.