"In 1939, on the eve of the Second World War," "Albert Einstein wrote a letter to the American President, Franklin Roosevelt." "Sir, the element Uranium may be turned into a new and important source of energy in the immediate future." "Certain aspects of the situation which has arisen seem to call for watchfulness and, if necessary, quick action on the part of the administration." "Extremely powerful bombs of a new type may thus be constructed." "The letter was about an application of Einstein's famous equation, e=mc²." "And his fear that the Nazis could use it to build an atomic bomb." "His letter set off a chain of events which led to the destruction of Hiroshima and Nagasaki." "Albert Einstein would later describe writing this letter as the one mistake of his life." "This is the story of his famous equation." "And how e=mc² changed history and Einstein forever." "On the eve of Second World War Albert Einstein, the most famous scientist in the world, was on holiday by the coast outside New York." "He was an instinctive pacifist who had fled Nazi Germany, and he had hoped to turn his back on the violence in Europe, and continue his work in peace." "But his summer was interrupted by a visitor who had also fled the Nazis." "The caller was Leo Szilard, another brilliant scientist and an old friend of Einstein's from Europe." "Szilard." "Herr Professor, there is something we must do." "Come in." "Leo Szilard had come to persuade his old friend that the world was threatened by a new weapon." "His aim was to convince Einstein that something had to be done." "Cookie?" "Herr Professor, I need your help." "Why?" "Are you on the run from the police?" "I wish it was that simple." "I want you to help me compose a letter." "It's a long way to come for help with your correspondence." "Not this correspondence." "I've never written a letter like this before." "I'm not even sure what I should say." "Who is the letter to?" "Roosevelt." "President Roosevelt." "Are you offering advice, or admonition?" "A warning." "I want to warn Roosevelt about the German bomb." "The Germans have many bombs." "Not one like this." "At least, not yet." "It's an atomic bomb, the Germans are going to be able to build an atomic bomb." "And if they are doing it, then so must we." "This meeting would one day come to haunt Einstein." "Because Leo Szilard had come to explain that the Nazi project he feared so much was an application of something Einstein himself had discovered," "the equation e=mc²." "E=mc² is the symbol of Einstein's genius." "It's an equation that sums up one of the most powerful truths about the universe." "It combines two ideas, which until Einstein came along, no one had ever dreamed could be connected in such a powerful way." "The idea of Mass." "And the idea of energy." "If you think about energy and mass it is not at all obvious that they're anything like the same thing." "I mean energy is something that moving objects have, and mass is something that every object possesses." "So really it's a bold step to try and link them in any way, let alone in a beautiful way that Einstein did." "Einstein's great insight was that energy, the thing that enables an object to move, and mass, essentially an objects weight, are not different, they are in fact the same thing." "Einstein really found that energy and mass are two sides of the same coin." "They're almost the same thing, so mass in a sense is energy waiting to be liberated." "In other words, according to Einstein, mass could be transformed into energy." "And energy into mass." "But Einstein's equation went even further." "It gave an exact value to the amount of energy contained within any given mass." "Energy equals mass times C - the speed of light, squared, a number that is absolutely huge." "This is Einstein's famous equation: e, energy equals m, mass, times c squared, the speed of light squared." "In metres per second:" "eighty nine thousand, eight hundred and seventy five million million, huge number." "That means you get an awful lot of energy for an extremely tiny amount of mass." "The implications of this neat equation were vast." "Well it means that there's enough energy in a glass of water to power a city like London for a week." "Hidden within every object around us is a huge store of energy." "Einstein published e=mc² in 1905." "And it changed the world." "It wasn't long before e=mc² solved one of the great mysteries of life on earth." "What really powers the sun?" "For generations this had baffled scientists." "Because if the sun just burned like a huge bonfire, the calculations showed it should have died out millions of years ago." "But Einstein's equation explained what was powering the sun." "In the sun's core, mass was constantly being converted into energy." "A process that can be sustained for billions of years." "Tiny particles were smashing together, and the mass lost in this reaction was transformed into energy." "And soon people began to think, if e=mc² can power the sun, could we use it to generate power on earth?" "Could we release the energy inside atoms for our own purposes?" "Within years, talk of getting energy out of the atom began to grip the popular imagination." "And at a scientific conference in 1935," "Einstein was asked whether he thought the atom would ever yield its energy." "His answer was to go down in scientific history." "The likelihood of transforming matter into energy is something akin to shooting birds in the dark in a country in which there are very few birds." "In other words, Einstein believed getting energy out of the atom was just not practical." "It would take an almost incalculable amount of energy to release energy even from even a single molecule." "Einstein was so dismissive because it was becoming clear that to release all that energy scientists would have to find an efficient way of breaking the atom apart." "And however hard they tried, it always took more energy to smash an atom than was released." "Kinda tough, huh?" "Kind of tough, yes." "But others were less dismissive." "In 1933 Hitler came to power in Germany." "Germany was one of the great centres of physics." "Some of its scientists were only too willing to work with Nazis." "And the Nazi war machine was eager to achieve what Einstein had said was impossible, to release energy from the atom, and create a bomb." "Unlike Einstein, Leo Szilard feared that energy could be released from the atom according to e=mc², and then used to construct a bomb." "And that fear had taken him to see Einstein that summer in Long Island." "The war in Europe is going to happen." "Hitler has planned for it." "And he has built up his arms." "And once he realises its power, he will not hesitate to construct an atomic bomb." "But that would take years." "Why years?" "To build such a bomb the reaction would have to take place in multiple millions of atoms simultaneously." "Maybe not simultaneously." "I think maybe there is another way that might be achieved." "Szilard was speaking with such confidence because he knew something Einstein did not." "Leo Szilard had worked out how to make e=mc² into a bomb." "In 1920, a young Leo Szilard had gone to study in Berlin." "There he witnessed the rise of the Nazis." "Szilard became worried by what this might mean for science and for the world." "Szilard was really scared because he had seen the Nazi terror first hand." "He warned his colleagues and then he himself left shortly after Hitler took power." "He was trying to draw as many friends as he could out of Nazi Germany, he saw how the terror was spreading." "But many brilliant physicists remained in Germany, and Szilard was fearful it was only a matter of time" "before someone would find a way of harnessing the power of e=mc² and make a bomb." "In fact, the first step had already inadvertently been taken, scientists had identified the type of substance they might need to turn mass into energy." "Yes radioactivity is already at work in medical fields..." "Radioactive iodine." "so if you will listen and watch at the same time when we hear the clicks." "Radioactivity is e=mc² in action." "Unstable elements like Radium and Uranium continually break down into ever smaller elements in order to become more stable." "What is actually happening is that tiny amounts of mass from the heart of an unstable atom are spontaneously released in the form of energy, which is carried away as radiation." "But finding the right type of substance to release energy according to e=mc² was only half the answer." "This scintillating character is very unstable, and as a consequence she radiates energy." "We call her radioactive." "Natural radioactivity was originally thought to be potentially very useful." "But the more that was understood about it, it was realised that this particular form of radioactivity whilst producing heat" "was not especially efficient." "The amount of heat given out was rather small." "This is radioactive iodine." "I'm now going to drink this." "Natural radioactivity was simply far too gentle for generating real power." "So scientists began to develop ways of improving upon nature." "In Germany, in Britain and in America machines were built to achieve nuclear fission, the splitting open of the atomic nucleus." "Many hoped this might release the vast amounts of energy potentially hidden within the atom." "Initially hopes were high, but again and again they hit Einstein's paradox." "They always had to put in far more energy than they ever got out." "The likelihood of transforming matter into energy is something akin to shooting birds in the dark in a country in which there are only very few birds." "It looked as though Einstein had been right after all." "e=mc² was simply a theoretical insight, not a practical solution to generating vast amounts of energy." "But then Einstein's friend, Leo Szilard had his first brainwave." "It happened day in 1933." "He suddenly realised everyone had been going about it the wrong way." "Attempts to release energy from matter had involved something called alpha particles." "And Szilard thought they were simply the wrong tool for the job." "Alpha particles consist of 2 protons and 2 neutrons and carry a positive electric charge." "The theory was that by smashing these particles at the nucleus they might blast it apart, converting some of the mass into energy." "It turned out to be not enough." "And even when the developments proceeded and accelerators were made to accelerate the alpha particles to higher and higher energies, still it needed more energy putting in than you actually got out from the process." "Leo Szilard recognized the problem was down to an invisible force, the positive charge of the alpha particle." "Because the nucleus of the target atom is also positively charged, just as magnet can repel each other," "the identical positive charges of the nucleus and the alpha particle would also repel each other." "It was this clash of electrical charge that was preventing the alpha particle from blasting apart the nucleus." "Alpha particles themselves carry a positive electric charge." "The nucleus has a positive electric charge so the two repelled each other and every time an alpha particle is sent towards the nucleus, it has a tendency to slew off to one side or the other." "Szilard realised what was needed was a particle able to attack the very heart of the charged nucleus." "And he thought he knew what would do it, the recently discovered neutron." "The neutron is a subatomic particle, just a quarter of the mass of an alpha particle." "And it has no electric charge." "Szilard reasoned that if a neutron could be fired at an atom's nucleus, it would not be repelled." "Instead it might bond to the nucleus itself." "And then the nucleus would become very unstable." "It might then split." "And as it did so, it could release some of its vast store of energy, according to e=mc²." "This was quite a stupendous discovery." "The neutron carried no electric charge and therefore it could approach the nucleus un-deflected and maybe even stick and interact with it." "In fact the impact of the neutron on the nucleus at the time was likened to the effect of the moon striking the earth." "Here was a means perhaps to make this slightly wobbly unstable nucleus absorb something that it couldn't help absorbing and then it would wobble even more and disintegrate." "Using the neutron was simply Szilard's first brainwave." "He went on to have another," "one that would become crucial to the making of the atomic bomb." "Szilard calculated that if you hit an atom with a neutron, as the atom divided, it would release not just energy, but two or three more neutrons." "And those neutrons might then be free to break apart further atoms." "And every time that happened a tiny bit of mass could be converted into a vast amount of energy." "Energy that at every step in the chain, would multiply and multiply." "It was a chain reaction." "So typically you would end up with two extra neutrons coming out." "So those two extra neutrons could then produce another fission process and produce two more neutrons, so you have 4 neutrons, that would then go to 8,16,32." "You have this multiplicative chain reaction process and the potential for that was immediately seen because each of these processes produces a large amount of energy." "What made Leo Szilard's idea so brilliant was that here, for the first time, was a way of getting energy out of the atom, without having to pump in vast amounts of power." "All you had to do was set off just one tiny neutron to trigger an unstoppable chain reaction." "Leo Szilard had potentially found a way to unleash the power of e=mc² on Earth." "But it was a discovery that terrified him." "Szilard's first reaction when he thought of the neutron was this is something that could become potentially a weapon." "His second thought was that if he could think of this then certainly his German colleagues who remain in Germany could think of it too and this really scared him." "Then, in 1938, less than a year before the outbreak of World War II, news came from his former colleagues in Germany," "news that truly alarmed Leo Szilard." "Scientists from several nations gathered for a routine conference heard a report of startling significance." "Word has just come through from Germany by way of Denmark that the German Physicists Hahn and Strassman have just verified that the uranium atom under neutron bombardment actually splits in to two parts." "In a lab in Berlin, the German team had struck lucky." "They had achieved nuclear fission, the first stage of Szilard's theoretical chain reaction." "In terms of physics it was an enormous breakthrough because up until that point it was a theory and theories are great but they need to be verified experimentally and it was the experimental verification of that which was really was the groundbreaking thing" "which meant wow this theory is true." "Within months, the Nazis began to stockpile Uranium." "They would later set up a military bomb programme." "Nazi money poured into fission research." "Nuclear physics was going to war." "For Leo Szilard, it was no longer possible for science to be neutral." "You are a scientist." "As am I." "It is best to remember that and let the military play their games." "I don't think that we can." "Not when some of our former colleagues in Germany are only too happy to work with the military." "That is their choice, if they wish to be so foolish." "They are still good scientists." "Some of the best." "And the military will give them all the assistance they need, but we also have good scientists." "Also some of the best." "So now you want us to go to war in the laboratory?" "That was precisely what Leo Szilard wanted to do." "The German scientists had achieved the first part of Szilard's theory, nuclear fission with neutrons," "and now he had to determine if the other stages of the process would follow." "By July 1939 in a lab at Columbia University," "Szilard with his colleague Enrico Fermi had conducted an experiment, that showed a chain reaction was possible." "There was now a real chance that e=mc² could be harnessed to make a bomb." "Szilard realised the fate of Mankind was now in the hands of science." "So he decided to use the fame and influence of the most eminent scientist of the age to alert the free world to the likelihood of a Nazi atomic bomb." "And that was why in July 1939, he called on his old friend." "Szilard's mission was to show Einstein that the formula he had thought up in 1905, e=mc², had a new and terrible reality with the element uranium." "Szilard had always been someone who believed he had the mission of saving the world." "And here abruptly through a scientific discovery was a very practical situation where the world might need saving." "Herr Professor." "I need your help." "It's a lot to have in your head as you knock on a door." "Szilard had come to tell Einstein about his recent work on the chain reaction, and that this breakthrough meant a bomb was now a real possibility." "Daran habe ich gar nicht gedacht." "I hadn't thought of that." "Sometimes I think I have thought of little else." "Certainly not for the past six years." "A secondary neutron reaction." "Multiple neutrons splitting multiple atoms and continuing." "Multiple neutrons splitting, multiple atoms, and continuing." "You are sure the chain reaction could be sustained?" "That's what Fermi and I have been working on." "So, so the release of energy would multiply, the reaction would be enormous, just imagine." "I know." "But just imagine, just imagine this." "Say if an atomic device was introduced into, say," "New York, say such a bomb was taken into New York Harbour in the hold of a ship." "And say it was detonated." "What would the destruction be?" "And soon such a bomb could be in the possession of Herr Hitler." "What should we say in this letter?" "Once Einstein heard about this he thought about it and within a few minutes he realised 'yes, this is what e=mc² means'." "At that point his abstract pacifism, if you will, would have become an intensely practical question," "'What can I personally do to limit somehow the possibility that these men could work on this weapon'." "The famous pacifist now began to write a letter to the President." "In the last four months it has been made probable..." "Calling for America to build the most powerful weapon ever constructed." "...to set up a nuclear chain reaction, in an amount of uranium." "Bigger." "Huh?" "Bigger, a..." "large mass... a large mass of uranium." "It is conceivable, so much is certain that an extremely powerful bomb of a new type may thus be constructed." "How powerful?" "You know how powerful." "Would Roosevelt?" "Should we not make it plain that this will be no ordinary bomb?" "Yes, yes we should." "It is almost certain that this can be achieved in the future." "Too hazy, 'the future'." "We need to say that the Germans can get it at any time." "I believe therefore it is my duty to bring to your attention the following facts and recommendations." "Yours, very truly, Albert Einstein." "Eight weeks later Albert Einstein's letter was taken to the White House." "I think that any letter written by Albert Einstein would get a President's attention." "Roosevelt's reaction was, 'so you're afraid that the Nazis are going to blow us up'." "'Yes'." "In that case he called in his military aide and he says this demands action." "It was now question of who would build an atomic bomb first, the Americans or the Nazis." "In the wilderness of New Mexico, the US government set up a top-secret project codenamed 'Manhattan'." "From Einstein's letter grew the biggest and most remarkable collaboration between science and the military the world has ever seen." "The government spent something like 2.2 billion dollars, which translated into modern dollars would be perhaps 40 or 50 billion dollars." "As much as it would later cost too send a man to the moon." "It was considered absolutely vital to the security of the allied forces." "The Manhattan project brought together some of the finest minds physics has ever produced." "Among them were many European scientists who had fled the Nazis, including Leo Szilard." "Einstein himself played no part." "The scientists were driven by the fear that the Nazis might get there first." "But in May 1945 before the bomb was complete all the calculations changed." "The Nazis surrendered." "On behalf of the army of the United States I accept your surrender." "The war in Europe was now over." "For some of the Manhattan project scientists, and for Einstein, there could now be no justification for the US to use an atomic weapon against anyone else." "Most of the scientists were idealists and some of them were very naive idealists." "Einstein was probably one of those." "He really was thinking in terms of a deterrence, trying to keep Germany from using this bomb." "But although there was no longer any threat from the Germans, work at Los Alamos continued." "And in July 1945, two months after the Nazi defeat, the bomb was ready." "The bloody war against Japan was still raging." "And the generals and politicians believed that the atomic bomb could bring about a swift end to the fighting and save thousands of allied lives." "Leo Szilard was horrified that the bomb might be dropped without a specific warning first being given." "He organised a petition among his colleagues, calling on the President to give this warning." "But there was now no stopping the use of the bomb." "They'd spent lots of money, they had a weapon that could win the war very quickly, and in that sort of situation they were going to use it." "The target had been selected, the Japanese city of Hiroshima." "On a bright morning in August 1945, the first atomic bomb was dropped." "It fell through the air for 43 seconds." "And then a single neutron started Szilard's chain reaction." "The energy released as the first atom of Uranium was split was only enough to make a grain of sand jump." "Then the chain reaction became unstoppable." "By the final generation of the chain reaction around two million million million million uranium atoms have been fissioned." "About point 6 grams of mass have been converted into a massive 12.5 kilotonnes of energy in just six tenths of a microsecond." "That's the power of a chain reaction and of e=mc²." "Just point six of a gram of mass converted into energy laid waste the city." "The Hiroshima bomb which was a small nuclear weapon by modern standards killed about 70,000 people almost immediately." "Caused radiation sickness and death by fire to another 70,000 people." "It destroyed 80 or 90% of all the buildings in the city." "It was absolutely devastating, and the world was never the same afterwards." "All this destruction had come about because of an application of e=mc²." "It's 9am Eastern War Time, and time for the CBS morning news." "The target Hiroshima is roughly the size of Memphis Tennessee or San Antonio Texas." "And that one atomic bomb has wiped out four and one tenth square miles of Hiroshima." "The Japanese for there part are already telling us that practically every living thing in Hiroshima has been burned to death and the dead are too numerous to be counted." "Einstein's response to the news of Hiroshima was horror." "In a very terrible way his formula had been demonstrated to the world in a sense for the first time." "Einstein felt he had to bare some responsibility for the development of the atomic bomb because without his letter to President Roosevelt in 1939 no bomb would have been ready to drop on Hiroshima in 1945." "Einstein's letter was critical because without it" "America would not have started working on the bomb in time to have a bomb before the end of World War 2." "In later years Einstein came to believe that writing the letter had been a mistake." "I made one mistake in my life, when I signed that letter to President Roosevelt advocating that the bomb should be built." "But perhaps I can be forgiven for that, because we all felt that there was a high probability that the Germans were working on this problem and they might succeed and use the atomic bomb to become the master race." "His distress grew when the nuclear arms race began." "Einstein realised that these nuclear weapons represented a threat to the world as a whole." "He once remarked that bullets kill people, nuclear weapons kill cities." "And that threat for him loomed more than anything else as a danger for the future of civilisation." "In the final decade of his life, Einstein now used his fame again, this time to warn the world it faced annihilation." "He campaigned against the spread and development of nuclear weapons." "One of his last acts was to sign a public declaration calling on world leaders to end war:" "Here then is the problem which we present to you, stark and dreadful and inescapable." "Shall we put an end to the human race; or shall mankind renounce war?" "But there is another side to e=mc² that only became clear after Einstein's death." "A side that is altogether more wonderful." "Because scientists have gone on to discover that e=mc² isn't just the equation of destruction, but also the ultimate equation of creation." "We know that a small amount of mass can be converted into an enormous amount of energy." "But the other side of the equation tells us something else and that is that it's possible for energy to condense back into mass." "This is the process that occurred at the very dawn of our universe, starting with the burst of energy known as the Big Bang." "Fifteen thousand million years ago, a singularity of pure energy, created in the Big Bang," "evolved and condensed into material and matter over a period of millions of millennia." "That energy slowly transformed into the mass that makes up everything in the universe." "You could think of the story of the early universe as one long realisation of e=mc²." "The universe begins in a ball of energy and slowly turns into mass." "Everything in our galaxy, and everything on our planet, even us, all in a sense exist because of the underlying workings of Einstein's equation." "So everything that has happened and the reason why we are here is underpinned by e=mc²." "Sadly Einstein never lived to see that his equation was truly the equation of creation, as well as destruction." "Politics is for the moment, while an equation is for eternity." "A hundred years ago when he derived the equation" "Einstein had no idea where his formula would lead." "e=mc² would go on to transform science and our understanding of the world." "For good." "And for ill."