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

• CPW
In summary, the conversation discusses the calculation of the yield of the Trinity nuclear test using dimensional analysis and the need for specific information, such as the radius of the fireball and the time of the photograph. An anecdote about Enrico Fermi estimating the yield using a scrap of paper is also mentioned. The conversation also touches upon the use of seismic readings to calculate the strength of underground nuclear tests.
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?

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

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.

DEvens and CPW
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.

## 1. How can a photo be used to calculate the strength of a nuclear explosion?

A photo can provide valuable information about a nuclear explosion, such as the size and shape of the mushroom cloud, the distance from the explosion site, and the type of explosion. By analyzing these factors, scientists can use mathematical models and simulations to estimate the strength of the explosion.

## 2. Can a single photo accurately determine the strength of a nuclear explosion?

No, a single photo cannot provide enough information to accurately calculate the strength of a nuclear explosion. Multiple photos from different angles and distances are needed to get a more comprehensive understanding of the explosion.

## 3. What other factors besides the photo are important in calculating the strength of a nuclear explosion?

In addition to the photo, the location and type of explosion, as well as atmospheric conditions, are important factors in calculating the strength of a nuclear explosion. These factors can affect the size and shape of the mushroom cloud and the amount of energy released.

## 4. Is it possible to calculate the strength of a nuclear explosion in real-time using a photo?

No, it is not possible to calculate the strength of a nuclear explosion in real-time using a photo. It takes time for scientists to analyze the photo and gather additional information to make an accurate estimation.

## 5. How accurate are the calculations of the strength of a nuclear explosion from a photo?

The accuracy of the calculations depends on the quality and quantity of the photos, as well as the availability of other important information. With advanced technology and techniques, scientists can make fairly accurate estimations of the strength of a nuclear explosion from a photo, but there may still be some margin of error.

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