Why Einstein Thought Nuclear Weapons Impossible

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 Hey this episode of veritasium was supported by viewers like you on patreon and by the longest-running supporter of this channel Audible and audible offers a free 30-day trial of their service including a free audiobook to everyone who has watched this video Just go to audible.com slash veritasium or text veritasium to 500 500 You know we're coming into summer, and I think this is a great time to get into audiobooks. If you're not already because audiobooks are a perfect companion for tons of summer activities like going on road trips or hiking or just hanging out at the beach I Always, try to get more stories into my life when I'm out you know doing activities that I love like biking up the hill and Audible has the greatest selection of audiobooks on the planet one book I would recommend to you that I've been listening to the making of the atomic bomb by Richard Rhodes This is the definitive Account with such exquisite detail about how the bomb was Constructed how all the scientists made it work and really how its transformed the world and you can download this book right now We're going to audible.com/veritasium or by texting veritasium to 500 500 and what I love about audible is that the books are yours to keep so you can go back and re-listen to them anytime even if You cancel your subscription so head on over to audible.com slash veritasium or text veritasium to 500 500 I want to thank audible for supporting me, and I want to thank you for watching

Channel: Veritasium

Views: 1,920,932

Rating: 4.9435825 out of 5

Keywords: veritasium, science, physics, nuclear, atomic bomb, chain reaction, neutron, nucleus, energy, nuclear power, einstein, e=mc2, weapon, nuclear weapons, nutron, nucular

Id: HD3k1hgbUXQ

Length: 7min 37sec (457 seconds)

Published: Mon Apr 30 2018

Reddit Comments

[u/shrimpyeti]

Very cool video! Can anybody explain how nuclear power plants today regulate the number of neutrons that are absorbed/how they are absorbed to maintain a constant power output?

[u/fish1479]

neat.

[u/hetero-scedastic]

So what you're saying is a nuclear reactor is a meme with a viral coefficient of one.

[u/__Shake__]

See? Sciences is a LIAR sometimes!