How did scientists know how much power the first Nuclear bomb would release?

Question

how did they know it wouldn't have put a whole in the universe
so it say

Answer 1

They knew that e=mc^2, where e is the energy, m is the mass, and c is the speed of light.

They knew how much the mass of the fissionable material was, but they did not know for sure what % would actually contribute to the explosion, and what % would be blown away by the initial explosion (it turns out that a very large percentage contributes to the explosion).

Also, once they thought they had an ideal on what the equivalent tons of TNT would be, they had not idea what effect this would have, because nothing anywhere near that powerful had ever been exploded.

In the end, it turned out to be more destructive than most thought it would (there were a few that thought it would continue unchecked causing the entire atmosphere to explode, but thankfully they were wrong).

Answer 2

Because a nuclear bomb does not happen by accident. You don't just put two pieces of Uranium or Plutonium together and then it explodes. You first have to understand all about the energy release mechanisms in your fissionable materials. Then you can multiply that by the number of nuclei in your engineering device and that is the upper limit for energy release. Any real world device will be less than that. So that makes for a figure of merit... how much of the theoretical energy has been released. And then it becomes an engineering problem, again, to do the calorimetry, i.e. to measure the real amount of energy released.

The reason why there was no "whole" made into the universe is because there are no such things. A bomb is a rather timid device in comparison to what nature does herself. A supernova, a black hole merger, now those are violent events. In comparison a nuclear device is just child's play. And of course one can quantify all this quite well. And the people who made the first bombs understood these things perfectly well.

Answer 3

Theory and experiment...just like any research and development project...were the basis for the first nukes (and all new ones thereafter).

Einstein's E = mc^2 was the theoretical basis for nuclear energy. The Manhattan Project done in Chicago during WWII was where the experiments were done.

What most people don't understand is that atoms don't split like so many billiard balls hit by the cue ball. No, they split only after capturing the bullet neutron (e.g., the cue ball), which raises the energy levels of the target atoms.

This is an important distinction because it means the bullet neutrons could in fact go too fast to be captured as well as too slow. Thus, like Goldilocks, the neutron bullet energy levels have to be just right for fission to occur. And much of the experimentation during the Manhattan Project focused on that issue.

The other issue was just how much energy could we expect when the physics package was detonated? Clearly, the amount of energy is predicated on how many atoms split. Unfortunately, not all the neutron bullets released by each splitting atom do any more splitting of other atoms. Some of the neutrons are too fast or too slow. Some just boogaloo out of the package into the surroundings.

So a lot of experimentation went into measuring controlled fission (like in a nuclear power plant) and into figuring out the best shape for the physics package that carries the nuclear material.

Consider 2^n; where n is the number of generations of neutrons and consequent atom splitting in the next generation. After n = 1 generation (the first one), there will be 2^1 = 2 bullets created to split two more atoms. These two atoms are the second generation n = 2; so they produce 2^2 = 4 bullets...and so on. After 2^23 generations, we have over 8 million atoms splitting and letting loose delE = (M - m)c^2 energy, where M is the mass of those 8 million atoms before splitting and m is the mass of the children atoms after the splitting. I mention 23 generations because that all happens in less than a second. From Einstein's E = mc^2, the mass difference M - m is the source of the nuclear explosion.

As awesome as a nuke explosion might be, it pales in comparison to the awesome energy of the entire universe. In addition, as I tried to explain above, nuke reactions don't just happen. Things have to be just right for a sustainable chain reaction of atoms splitting. The universe just doesn't have the right stuff for a nuke, of comparitively very little energy, to set it off.

Answer 4

Well, they did not exactly know. It was only a rough estimate. They knew that a single fission of U235 could produce 931 MeV of energy (a tremendous amount). But they had not bargained for such vast destruction in the twin cities. Even the after effects of the bomb could not be explained by them. They did test the bomb in some desert, I think. So they had pretty much a good idea how much power it would give.

:)

Answer 5

A lot of it was just guess work. but they probally had some Idea of how much weight they would need to put it to even get it to work. This is an interesting question, I'll give you a star. I'm not totally sure, but I think they tried detonating one as a test, before actually droping the first one in war.