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Now that we have nuclear weapons and nuclear power plants you might think that it was always
Inevitable that we would be able to harness the energy inside the nucleus of atoms
But that was far from the case in fact serious scientists, thought the idea was laughable like Nobel laureate Robert
Millikan who in 1928 said there is no likelihood man can ever tap the power of the atom
The glib supposition of utilizing atomic energy when our coal has run out is a completely unscientific
Utopian dream or as Rutherford put it anyone who expects a source of power from the transformation of these atoms is talking moonshine
now there was good reason for their pessimism when Becquerel first observed to radioactivity he thought it was a phenomenon similar to
phosphorescence
That's when you shine radiation like light onto an object
And it absorbs that energy and later
Reradiates it in a different part of the spectrum now uranium ore was known to do this as I witnessed firsthand. Oh, yeah
X yes
fluorescent uranium ore
Yeah
Here, it's absorbing UV light and reradiating it as visible light in
1896 Becquerel performed experiments where he placed uranium ore in the sunshine on top of some wrapped up
Photographic film he found that the film was exposed
Seemingly by invisible rays from the uranium ore that penetrated the paper when the uranium was excited by the sunlight
But one day when he went to do his experiment the weather in Paris was lousy so he put the uranium and the photographic film
Inside a drawer and a few days later even though the uranium hadn't seen the Sun
He decided to develop the film anyway
And what he found was that the photographic film had been exposed just as before
Even though the uranium was not excited by sunlight
So this was not a phosphorescence phenomenon some type of radiation and therefore energy was coming out of a rock
unprovoked
But how could a seemingly inert object like a rock give off energy
Where is it getting that energy from it was a mystery that seemed to violate the law of conservation of energy?
That is until Einstein published his famous e equals mc-squared
Which suggested a source of energy for the?
Might be the mass of the nucleus
Just a tiny bit of mass can give you a lot of energy and this premise was enough for science fiction writers to let their
Imaginations run wild like HG Wells who in 1914 published the book the world set free
Which includes the first mention of the words atomic bomb he envisioned a uranium based hand grenade that would continue to explode
indefinitely but to scientists this was completely detached from reality as Einstein in 1933 put it there is not the
slightest indication that nuclear energy will ever be obtainable it would mean that the atom would have to be shattered at will and
That's just the thing people had no ability to make a nucleus do
Anything all we were observing was the natural process of radioactive decay atoms of a particular
Unstable isotope decaying at random with some characteristic half-life
And the energy given off although immense on the scale of an atom is pretty insignificant on the scale of people and the world
the fission of a single uranium atom releases
Twenty times less energy than the amount required to raise a grain of sand the thickness of a piece of paper
Now up until 1932 the only known particle in the nucleus was the proton so if you wanted to alter a nucleus you could conceivably
Fire a proton at it
But since the nucleus and the proton are both positively charged they repel
so you'd have to fire the proton in with such high speed and accuracy to get it to hit and stick to a target and
Even then if you're successful you've only affected one nucleus
Which at best can't even lift a grain of sand
So you can see why the Nobel Prize winners were saying nuclear weapons not gonna happen
But then comes the discovery of the neutron and the neutron changes everything
Because as an uncharged nuclear particle it can drift
Ghostly undeflected through matter until it hits a nucleus
Transforming it into something else and this leads to the Epiphany of a man named Leo Szilard
Now's a lard read the world set free, so he's already imagined a future in which nuclear energy is harnessed by weaponry
And he remembers the exact moment he comes up with this idea as he's crossing the street in London
He says it suddenly occurred to me that if we could find an element which is split by neutrons and which would emit two neutrons
when it absorbed one Neutron then such an element
If assembled in sufficiently large mass could sustain a nuclear chain
reaction
In other words the neutron
Enables us to trigger
nuclear reactions at will and if there's a nucleus which when it splits in this way releases two neutrons it could trigger more and more
Fission's and an exponentially increasing rate the nucleus that has this property is
uranium-235
In fact on average it releases two and a half neutrons every time it divides
Now all of a sudden you have the possibility of splitting zillions of nuclei
simultaneously releasing incredible amounts of energy all at once
That's an atomic bomb now if you want more control over this release of energy as in a nuclear power plant
well
Then you have to absorb a few neutrons so that the fission of one nucleus only
Causes the fission of one other nucleus on average
Then you have a steady chain reaction that emits the same amount of energy each instant the challenge is that this is like
Balancing on a knife-edge absorb too many neutrons and the chain reaction quickly decays to nothing absorb too few and the rate of reactions
Increases exponentially and soon you're back to a bomb or Chernobyl so if not for the existence of the neutron a neutral
nuclear particle to trigger reactions that occurs in greater numbers relative to protons in the larger nuclei meaning
They're likely to be given off when a large nucleus splits well, then maybe as many brilliant scientists suspected
It would be impossible to harness the energy in the nucleus
But as it is in our universe the neutron is the hero or the villain of nuclear physics
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