At 5:30 a.m., dawn on July 16 1945, in a small town called Alamogordo, New
Mexico, the course of human history was changed. The first atomic bomb was
detonated that day, and sealed the fate of humanity. It took the work of many people
to accomplish this engineering feat. But the principle leader of that Manhattan
Project, and a man considered the father of the atomic bomb, was Robert
Oppenheimer. After witnessing its awesome power on that fateful day, Oppenheimer was
so taken aback, he quoted a verse from the sacred Hindu text the Bhagavad Gita.
"Now I am become death, the destroyer of worlds"
we know it's awesome power, but how exactly does an atom bomb work?
An atom bomb works in the principle that when you break up a nucleus of an atom, a
large amount of energy is released. Why? Because it takes a large amount of
energy to keep the nucleus bound together. When you split it apart the
energy is released. the analogy is like a stack of bowling pins, when you hit it
with a bowling ball, all the energy that you used in stacking them, is released.
You can think of the nucleus of an atom as being similarly stacked together. Physics
purists may ding me for this analogy, but for the purposes of simplification, this
is a good way to think of it. Scientists chose the biggest, heaviest nucleus that
is found in nature to be the best candidate for splitting - uranium. Uranium
is unique in that one of its isotopes is the only naturally occurring element on
earth that is capable of sustaining a nuclear fission reaction. A uranium atom
has 92 protons and 146 neutrons together to give an atomic mass of 238 or
U238. A very small portion of uranium, when it is mined, is in the form of an isotope
U235 this isotope has the same 92 protons but only 143 neutrons, or three
fewer than U238. U235 is highly unstable, which makes it
highly fashionable or splittable. When uranium U235
is slammed by a neutron, it becomes uranium 236. U236 it's so unstable that
it almost immediately splits into two more stable atoms Krypton and Barium. In the
process of splitting and creating two more stable atoms, a whole bunch of
energy is release, along with three more neutrons. These three neutrons fly out
and slam more U235 atoms. And thus, a chain reaction occurs, causing more and
more U235 to be split, and ultimately causes a huge explosion. So what's the
big deal why don't more countries have the bomb. Well, the problem is that
natural uranium contains only 0.7% of this U235 isotope, and a whole bunch of
it is needed to make even one atomic bomb.
so mined natural uranium has to be enriched to get U235.
Sometimes this enrichment is done by turning it into a gas and letting the
lighter gas flow through a one-way barrier, so that it rises to the top,
because U235, as you might guess, is lighter than U238. Another engineering
challenge is to create a vessel with the correct shape and material to contain
the neutrons after fissioning so that they do not escape, but rather cause more
atoms to fission. And it is lined with a special mirror so as to force neutrons
back into the fissionable material rather than escape the vessel. Then the
correct amount of fissionable material has to be placed inside this vessel. This
is called a "super critical mass." There has to be enough Mass to sustain an
uncontrollable chain reaction resulting in an explosion. And finally, the super
critical mass has to be kept apart until you're ready for an explosion. Otherwise
an explosion can occur when you don't want it. The reason is because these
isotopes aren't stable, and are throwing off neutrons randomly. So the mass has to
be kept apart so that it is subcritical until ready to be exploded. In an atom
bomb, two subcritical masses are slammed together usually with a conventional
bomb contained inside the outer bomb. This conventional explosive charge
inside the container initiates the chain reaction to produce your typical mushroom cloud.
And where exactly does all that energy come from? It comes from Einstein's
famous equation E equals MC squared. The mass of the material left over from the
nuclear bomb is slightly less than before the explosion, only about 0.1%
less. And that 0.1% is what causes that huge explosion. Imagine how big that
explosion would be if all the mass, 100% is converted to energy. we need to thank
our lucky stars that although the concept of an atom bomb is simple the
process of actually creating a bomb is not so simple.
Arvin Ash here. If you like our videos please support us by subscribing.
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