I think I am safe in describing the years of my lifetime and probably including most of yours as perhaps the most turbulent in history. With that in mind I like to entitle this talk as "Six years that changed the world forever" with a sub title of "From the Discovery of Nuclear Fission in 1939 to the dropping of atom bombs in 1945 and proof of Einstein's corollary, E=MC2)
First let me describe what Einstein deduced back around 1910. That little equation postulated that energy and mass (or matter) are really the same thing, just in different form. It is not exactly the same but think of energy and matter being like ice and water! All you have to do is heat up the ice and it turns into water. It is not the same for matter! You have to do something different to get matter to change into energy. In the case of Uranium or Plutonium you have to induce a "chain reaction" whereupon this "matter" of its own free will and accord disintegrates itself into pure energy.
I expect you may remember those old timey wedding vows, "What God has joined together, let no man put asunder." Well, that is what it looks like we may have done!
If you are satisfied that something truly momentous happened at the "Big Bang" of creation some 15 or so billion years go, today's theory is that out of nothing or something the theoretical physicists call a "singularity", came a tremendous quantity of energy in a form still under consideration as to what it was like. You have probably heard of the so-called "string theory" in which the energy is likened to a vibrating string, having no discernable physical mass, just vibrating energy at millions of degrees temperature. As the temperature dropped, this vibrating energy eventually coalesced into matter from which our universe came. That's the part about "What God has put together." It has taken man a long time to learn how to reverse that -- you know, "putting it asunder".
`Now let me tell you a little of what we think we know about Uranium or Plutonium as examples. It is the same for both. They are slowly disintegrating as we speak and were probably both created shortly after the original "Big Bang". Each of these has a "Half Life" deduced from measurements by our physicists as to how long before there is only half of what there was -- due to self disintegration. By calculating backwards, it appears that Uranium may have been around as long as one of the current estimates of the age of our universe. Uranium's half life is thought to be 4.5 billion years (Plutonium's is only 713 million). Both may have been created at the same time but natural Plutonium has long since disappeared. So 4.5 billions years ago there should have been twice as much Uranium as there is today and 9.0 billion years ago about 4 times as much as we have today. Fortunately for the sake of the atom bombs, we have learned how to make fissionable Plutonium 239 out of Uranium 238 by adding a neutron to its nucleus in an atomic pile like the Manhattan Project plant built during WWll at Hanford Washington. We only had enough fissionable Uranium to make one bomb - the " Little Boy" -- the one dropped on Hiroshima. We only discovered Plutonium and how to make it in 1942 -- giving us a relatively unlimited supply for bombs.
If you postulate that Uranium and Plutonium were created at the same time after the "Big Bang", it is easy to visualize that natural Plutonium has long since disappeared through self disintegration -- the Plutonium atoms are heavier than Uranium atoms and probably a little more fragile, perhaps contributing to faster disintegration.
So some of the current theory goes anyway.--------------
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