Most people are aware of the destructive force held within an atomic weapon, but what are physical forces are conspiring in order to cause such a violent explosion?

A History of Radioactivity

In 1896, French Physicist Henri Becquerel discovered the phenomenon later known as “radioactivity,” wherein certain elements (generally the larger, and thus more unstable, ones) have a tendency to spontaneously emit particles (later named alpha particles, beta particles and gamma rays) and in so doing, to “decay” by changing their nuclear configuration. This phenomenon was later studied by such notable scientists as New Zealand’s Ernest Rutherford (for whom the element “Rutherfordium” was later named) and France’s Marie and Pierre Curie.

In 1934, Italian physicist Enrico Fermi (for whom Fermilab, a famous particle accelerator laboratory near Chicago was named) was using Uranium to investigate the inner workings of the atomic nucleus. To do this, he began bombarding uranium atoms with neutrons. His studies began to show that when he did this, he often ended up with less uranium and more of other, lighter elements. What he realized was happening was that the neutrons were able to “split” the nucleus of the Uranium into smaller elements.

There was a problem in this, however. The elements which were created by the splitting of Uranium seemed to be less massive than the original atom. Somewhere along the way, there was some missing mass!

The answer to this, like so many other things, can be found in the theories of Albert Einstein, who, almost thirty years earlier, had developed his famous formula, E = mc². While Fermi did not yet realize it, the missing mass in his experiment had been turned into pure energy and released thusly, though his experiment was on such a small scale that he hadn’t even realized the tiny explosion occurring when the single atoms were split. Fermi had unknowingly been the first person to successfully induce a nuclear fission reaction.

It wasn’t until later experiments were performed in 1938 by Otto Hahn and Fritz Strassman that the correlation between Einstein’s equation and nuclear fission were finally made. And it was at this point that physicists began to realize that there was some very awesome potential in this new “nuclear theory.”

How Does a Nuclear Chain Reaction Occur?

It wasn’t long after Einstein’s theory was applied to nuclear fission that scientists began to realize that the possibility existed to construct a “superweapon” which made use of this phenomenon, for according to Einstein’s equation, just a little bit of mass (a small ball of Uranium, for example), could result in a tremendous amount of energy being released.

The question that remained unanswered, though, was whether or not nuclear fusion could cause a chain reaction. It was known that when an atom was split apart by neutron bombardment, even more neutrons were often created from within the original radioactive nucleus. If these newly-freed neutrons were moving with enough velocity, it was thought, they could then cause other, surrounding atoms to spit, which would then release more neutrons, splitting even more atoms, freeing up even more energy… and this would continue until all of the atoms in the radioactive substance were split and massive amounts of energy were created, in the form of an explosion.

The fact that this “chain reaction” could indeed be induced cleared the way for the construction of the atomic bomb.

Einstein and “The Bomb”

Despite common misconceptions, the equation for mass/energy equivalence was the only thing Albert Einstein really contributed to the atomic weapons project. While it is often assumed by those who aren’t familiar with the actual history that Einstein had direct involvement in “The Manhattan Project,” or even that he built the thing himself, perhaps in his basement, Einstein was actually rather morally opposed to the use of such weapons.

After realizing the extent of what was happening in Europe and the Pacific during the height of World War II, Einstein did come around to realizing that there was serious danger that Hitler might be able to build a bomb himself, which would truly be a devastating eventuality. He knew that the United States had no choice but to beat him to the punch, and as a result, he set his pacifism aside long enough to write president Franklin D. Roosevelt a letter to this effect.

While it is unknown what (if any) effect Einstein’s letter had on the president, the Manhattan project did indeed commence, and the rest, as they say, is history.

The devastating reality of nuclear fission was true proof of Einstein’s theory that mass could be turned into pure energy.

But it was proof that Einstein would surely have rather done without.

References:

Davies, P. (1995). About Time - Einstein's Unfinished Revolution. New York: Simon & Schuster.

Michael Guillen, P. (1995). Five Equations that Changed the World: The Power and Poetry of Mathematics. New York, NY: MJF Books.

Nuclear Engineering. (n.d.). The History of Nuclear Energy. Retrieved 1 24, 2007, from Nuclear Engineering: http://nova.nuc.umr.edu/nuclear_facts/history/history.html