Think of an equation, any equation. If you are a mathematician or physicist, or generally interested in science, you have many equations to choose from. Perhaps you are now thinking of one of Maxwell’s equations, possibly the second main theorem of thermodynamics? Possibly you went all the way back to Pythagoras? If you are not a mathematician, physicist or generally interested in science, there is a good chance that you thought of E=mc2. And then the big question is: do you know what the equation tells us? If you already know that, you should read on, to check that I explain it satisfactorily. If you don’t know, you should also read on – imagine how embarrassing it would be if absolutely everyone in Norway, apart from you, read the entire article? The Netflix series “In Search of Eternity” is about infinity, and not surprisingly, “E=mc2” is one of the equations on the blackboard behind mathematician Steven Strogatz. By the way, did you know that it is impossible to screenshot from Netflix? I had to use my phone to take a picture of the computer screen, as if I belonged to my own grandparent regeneration. Photo: Netflix Hollywood’s favorite equation Where the father of the equation, Albert Einstein, has become the symbol of intelligence, the equation itself has become a pop cultural symbol of complicated science. Writing E=mc2 on a blackboard, or in a notepad, is the easiest and clearest way to mark that a character is working with something advanced, which is inaccessible to most people. But is E=mc2 really that inaccessible? E=mc2, or the law of mass energy as it is also called, is a consequence of the special theory of relativity. And the theory of relativity, at least the general theory, must be said to be relatively inaccessible to the average crowd. Are you one of those people who first think of this Mariah Carey record when you hear about E=mc2? Photo: Island records To you science professionals on Twitter who get pissed off every time journalists portray mathematics and physics as something difficult and foreign – sorry so much, but the theory of relativity is just a bit problematic for most people to get a good grip on, so honest must we be. The law of mass energy, however, is not necessarily as inaccessible as Hollywood makes it out to be. And if you don’t necessarily understand all the implications and mechanisms (spoiler: you probably won’t understand all the implications and mechanisms), then it’s not that difficult to grasp the gist of the law, and by extension to understand a bit more of how nature works . What do you know about E=mc2? I know what there is to know I know a lot, thanks for asking I at least know what it’s about I think I might know a little about what it’s about I’ve only heard of it, don’t know what it means I’ve never heard if it Show result Energy can be used for what? First we have to look at what each individual letter in the equation means. E simply stands for energy. In physics, in contrast to, for example, the crystal industry, one operates with a very concrete form of energy – the ability to perform work. We measure this, for example, in joules, which is the energy required to produce one watt in one second. M stands for mass, which we measure in kilograms. Unfortunately, that does not mean that it is the same as what we call weight or heaviness, that would be too simple. If you stand on a bathroom scale on Earth, which is probably the only planet you have stood on a bathroom scale on, it shows a number. For example 80 kilos. If you stand on a bathroom scale on the Moon, it will, on the other hand, show just over 13 kilos. Your mass has not changed, but the force of gravity has. Mass is thus the amount of matter, while weight is the force the matter exerts on the substrate. Having said that – as long as you weigh something close to the Earth’s surface, which you like to do, we can say that the scale shows the mass. C is a bit more straight forward, it is simply the speed of light in an empty space. About 300,000 kilometers per second. The two at the end means that the speed of light must be multiplied by itself – the speed of light raised to the second. Which means you end up with a very high number. OK, then we know that E=mc2 can be translated to energy is equal to mass times the speed of light squared. And what does that mean? This means that all mass has energy, and that all energy has mass. In other words: Matter can turn into energy, and perhaps a little less intuitively – energy can turn into matter. The difficult fusion That mass can be turned into energy is something we continuously benefit from, it is precisely the mechanism that turns the Sun into our heater. Hydrogen nuclei combine to form helium. The mass of the helium nucleus is less than the combined mass of the two hydrogen nuclei. Where has the surplus mass gone? It has become energy, which radiates from the Sun. This is called fusion. We have, for a number of years, tried to learn how to utilize fusion in the context of power production, but have still not been able to crack the code. Recently, researchers at the National Ignition Facility in California managed to get more energy out of a laser-induced fusion than they put in. An important step on the road to fusion power plants, but we are still a few decades away. In nuclear power plants, we use the opposite mechanism, fission. An atomic nucleus splits into two smaller parts, which together have less mass than the nucleus of which they were a part. The remaining mass becomes heat energy, which we can in turn convert into electricity. Do you want to use your knowledge that matter can turn into energy for something a little more destructive than power generation? Then you can, for example, make a bomb. A hydrogen bomb works somewhat in the same way as the Sun – i.e. by means of fusion. An atomic bomb is like a small nuclear power plant, where fission causes the explosion. This photo was taken on Einstein’s 72nd birthday, in 1951. The paparazzi shouted that he had to smile for the camera, Einstein chose to giggle. The result was a photograph of the iconic battle. Photo: TopFoto / Topfoto Bitte litt masse = lots of energy Once we are on the topic of bombs, it is time to have a chat about quantity ratios. Little Boy, the atomic bomb that exploded just over 500 meters above Hiroshima in August 1945, contained 64 kilograms of uranium. Only a scant gram of this was converted into energy. This scant gram of mass nevertheless turned into enough energy to destroy a city, and kill tens of thousands of people instantly. The law of mass energy does not say that energy is equal to mass, period, it says that energy is equal to mass times the speed of light raised to the second. It can also be written in the following way: E = m times 89,875,517,873,681,176 It is difficult to relate to such high numbers, but the fact that the number is so high nevertheless tells us something in plain text: A little mass can turn into tremendous amounts of energy , and enormous amounts of energy are required to make a little mass. It is this bias that makes atomic bombs so horrifically effective. It is also this bias that means that we do not see so much energy that turns into mass. But it will be just as full. If you kick a ball, you add energy to the ball. The ball, when it is in motion, will have a tiny bit more mass than it had when it was at rest. This is not particularly intuitive, and even less measurable, but you simply have to just accept that it is like that. Two sides of the same coin Let’s be completely honest – the Mass Energy Act has more, and far more complicated, implications than what we have gone through so far. Equations that are a consequence of the theory of relativity tend to have that. But if you, the next time you see E=mc2 on a blackboard in a TV series, now think “that says something about mass and energy being two sides of the same thing, that mass can become energy, and that energy can turn into mass”, then it’s a little more satisfying than just thinking “that means the character who wrote that on the board is very smart”, and that’s always something.
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Albert Einstein and the equation above all equations – Long reading from news Trøndelag
