How Quantum Physics Explains Action Films

One of the key ideas used by cosmologists (yes, physics again, sorry) to explain away questions asked by annoying philosophical types is known as the anthropic principle. This has two forms (strong and weak) but the idea remains the same for both; that the reason for a situation being as it is is because, if it wasn’t, we wouldn’t be around to ask that question. For example, one might ask (as Stephen Hawking did in ‘A Brief History of Time’) why the universe is around 10 billion years old, a decidedly awkward question if ever there was one. The anthropic principle provides the simplest answer, stating that since organic life is such a complicated business and that the early universe was such a chaotic, unfriendly place, it is only after this vast amount of time that life forms capable of asking this question have been able to develop.

This answer of ‘because we’re here’ is a wonderfully useful one, albeit one that should be used with caution to avoid not answering valid question, and can be applied to problems that do not concern themselves directly with physics. One example concerns the origin of the human race, as we are all thought to stem from just a few hundred individuals who lived in East Africa’s Rift valley several million years ago. At that time our knowledge of weapons, fighting and general survival was relatively scant, and coming face to face with any large predator would have been a fairly assured death sentence; the prehistoric equivalent of a smart pride of lions, or even some particularly adverse weather one year, could have wiped out a significant proportion of the human race as it stood at that time in just a few months. Despite the advantages of adaptability and brainpower that we have shown since, the odds of natural selection were still stacked against us; why did we arise to become the dominant multicellular life form on this planet?

This question can be answered by listing all the natural advantages we possess as a species and how they enabled us to continue ‘evolving’ far beyond the mere natural order of things; but such an answer still can’t quite account for the large dose of luck that comes into the bargain. The anthropic principle can, however, account for this; the human race was able to overcome the odds because if we hadn’t, then we wouldn’t be around to ask the question. Isn’t logic wonderful?

In fact, one we start to think about our lives and questions of our existence in terms of the anthropic principle, we realise that our existence as individuals is dependent on an awful lot of historical events having happened the way they did. For example, if the Nazis had triumphed during WWII, then perhaps one or more of my grandparents could have been killed, separated from their spouse, or in some way prevented from raising the family that would include my parents. Even tinier events could have impacted the chance of me turning out as me; perhaps a stray photon bouncing off an atom in the atmosphere in a slightly different way could have struck a DNA molecule, causing it to deform the sperm that would otherwise have given me half my genes and meaning it never even made it to the egg that offered up the other half. This is chaos theory in action, but it illustrates a point; for the universe to have ended up the way it has depends on history having played out exactly as it has done.

The classic example of this in quantum physics is the famous ‘Schrodinger’s Cat’ experiment, in which a theoretical cat was put into a box with a special quantum device that had a 50/50 chance of either doing nothing or releasing a toxic gas that would kill the cat. Schrodinger’s point was that, when the cat is put into the box, two universes emerge; one in which the cat is dead, and one in which it is alive. Until we open the box, we cannot known which of these universes we are in, so the cat must be thought of as simultaneously alive and dead.

However, another thought experiment known as the ‘quantum suicide’ experiment takes the cat’s point of view; imagine that the cat is an experimenter, and that he is working alone. Imagine you are that experimenter, and that you had stayed in the box for five iterations of the 50/50 life/death random event. In 31 out of 32 possible futures, you would have been gassed, for at least once the device would have selected the ‘death’ option; but in just one of these 32 alternative futures, you would still be alive. Moreover, if you had since got out of the box and published your results, the existence of those results is solely dependent on you being that lucky one out of 32.

Or, to put it another way, consider a generic action hero, in the classic scene where he runs through the battlefield gunning down enemies whilst other, lesser soldiers fall about him from bullets and explosions. The enemy fire countless shots at him, but try as they might they can never kill him. They try, but he survives and the film reaches its triumphant conclusion.

Now, assuming that these enemies are not deliberately trying to miss him and can at least vaguely use their weapons, if our action hero tried to pull that ‘running through a hail of bullets’ stunt then 999 times out of a thousand he’d be killed. However, if he was killed then the film would not be able to reach its conclusion, since he would be unable to save the heroine/defeat the baddie/deliver a cliched one-liner, and as such the story would be incomplete.  And, with such a crappy story, there’s no way that a film would get made about it; therefore, the action hero must always be one of the lucky ones.

This idea of always triumphing over the odds, of surviving no matter what because, if you didn’t, you wouldn’t be around to tell the tale or even be conscious of the tale, is known as quantum immortality. And whilst it doesn’t mean you’re going to be safe jumping off buildings any time soon, it does at least give yo a way to bore the pants off the next person who claims that action movies are WAAYYYY too unrealistic.

Advertisement

The Story of the Atom

Possibly the earliest scientific question we as a race attempted to answer was ‘what is our world made of’. People reasoned that everything had to be made of something- all the machines and things we build have different components in them that we can identify, so it seemed natural that those materials and components were in turn made of some ‘stuff’ or other. Some reasoned that everything was made up of the most common things present in our earth; the classical ‘elements’ of earth, air, fire and water, but throughout the latter stages of the last millennia the burgeoning science of chemistry began to debunk this idea. People sought for a new theory to answer what everything consisted of, what the building blocks were, and hoped to find in this search an answer to several other questions; why chemicals that reacted together did so in fixed ratios, for example. For a solution to this problem, they returned to an idea almost as old as science itself; that everything consisted of tiny blobs of matter, invisible to the naked eye, that joined to one another in special ways. The way they joined together varied depending on the stuff they made up, hence the different properties of different materials, and the changing of these ‘joinings’ was what was responsible for chemical reactions and their behaviour. The earliest scientists who theorised the existence of these things called them corpuscles; nowadays we call them atoms.

By the turn of the twentieth century, thanks to two hundred years of chemistry using atoms to conveniently explain their observations, it was considered common knowledge among the scientific community that an atom was the basic building block of matter, and it was generally considered to be the smallest piece of matter in the universe; everything was made of atoms, and atoms were fundamental and solid. However, in 1897 JJ Thomson discovered the electron, with a small negative charge, and his evidence suggested that electrons were a constituent part of atoms. But atoms were neutrally charged, so there had to be some positive charge present to balance out; Thomson postulated that the negative electrons ‘floated’ within a sea of positive charge, in what became known as the plum pudding model. Atoms were not fundamental at all; even these components of all matter had components themselves. A later experiment by Ernest Rutherford sought to test the theory of the plum pudding model; he bombarded a thin piece of gold foil with positively charged alpha particles, and found that some were deflected at wild angles but that most passed straight through. This suggested, rather than a large uniform area of positive charge, a small area of very highly concentrated positive charge, such that when the alpha particle came close to it it was repelled violently (just like putting two like poles of a magnet together) but that most of the time it would miss this positive charge completely; most of the atom was empty space. So, he thought the atom must be like the solar system, with the negative electrons acting like planets orbiting a central, positive nucleus.

This made sense in theory, but the maths didn’t check out; it predicted the electrons to either spiral into the nucleus and for the whole of creation to smash itself to pieces, or for it all to break apart. It took Niels Bohr to suggest that the electrons might be confined to discrete orbital energy levels (roughly corresponding to distances from the nucleus) for the model of the atom to be complete; these energy levels (or ‘shells’) were later extrapolated to explain why chemical reactions occur, and the whole of chemistry can basically be boiled down to different atoms swapping electrons between energy levels in accordance with the second law of thermodynamics. Bohr’s explanation drew heavily from Max Planck’s recent explanation of quantum theory, which modelled photons of light as having discrete energy levels, and this suggested that electrons were also quantum particles; this ran contrary to people’s previous understanding of them, since they had been presumed to be solid ‘blobs’ of matter. This was but one step along the principle that defines quantum theory; nothing is actually real, everything is quantum, so don’t even try to imagine how it all works.

However, this still left the problem of the nucleus unsolved; what was this area of such great charge density packed  tightly into the centre of each atom, around which the electrons moved? What was it made of? How big was it? How was it able to account for almost all of a substance’s mass, given how little the electrons weighed?

Subsequent experiments have revealed an atomic nucleus to tiny almost beyond imagining; if your hand were the size of the earth, an atom would be roughly one millimetre in diameter, but if an atom were the size of St. Paul’s Cathedral then its nucleus would be the size of a full stop. Imagining the sheer tinyness of such a thing defies human comprehension. However, this tells us nothing about the nucleus’ structure; it took Ernest Rutherford (the guy who had disproved the plum pudding model) to take the first step along this road when he, in 1918, confirmed that the nucleus of a hydrogen atom comprised just one component (or ‘nucleon’ as we collectively call them today). Since this component had a positive charge, to cancel out the one negative electron of a hydrogen atom, he called it a proton, and then (entirely correctly) postulated that all the other positive charges in larger atomic nuclei were caused by more protons stuck together in the nucleus. However, having multiple positive charges all in one place would normally cause them to repel one another, so Rutherford suggested that there might be some neutrally-charged particles in there as well, acting as a kind of electromagnetic glue. He called these neutrons (since they were neutrally charged), and he has since been proved correct; neutrons and protons are of roughly the same size, collectively constitute around 99.95% of any given atom’s mass, and are found in all atomic nuclei. However, even these weren’t quite fundamental subatomic particles, and as the 20th century drew on, scientists began to delve even deeper inside the atom; and I’ll pick up that story next time.

The Age of Reason

Science is a wonderful thing- particularly in the modern age where the more adventurous (or more willing to tempt fate, depending on your point of view) like to think that most of science is actually pretty well done and dusted. I mean, yes there are a lot of the little details we have yet to work out, but the big stuff, the major hows and whys, have been basically sorted out. We know why there are rainbows, why quantum tunnelling composite appears to defy basic logic, and even why you always seem to pick the slowest queue- science appears to have got it pretty much covered.

[I feel I must take this opportunity to point out one of my favourite stories about the world of science- at the start of the 20th century, there was a prevailing attitude among physicists that physics was going to last, as an advanced science, for about another 20 years or so. They basically presumed that they had worked almost everything out, and now all they had to do was to tie up all the loose ends. However, one particular loose end, the photoelectric effect, simply refused to budge by their classical scientific laws. The only person to come up with a solution was Max Planck who, by modelling light (which everyone knew was a wave) as a particle instead, opened the door to the modern age of quantum theory. Physics as a whole took one look at all the new questions this proposed and, as one, took a collective facepalm.]

In any case, we are now at such an advanced stage of the scientific revolution, that there appears to be nothing, in everyday life at least, that we cannot, at least in part, explain. We might not know, for example, exactly how the brain is wired up, but we still have enough of an understanding to have a pretty accurate guess as to what part of it isn’t working properly when somebody comes in with brain damage. We don’t get exactly why or how photons appear to defy the laws of logic, but we can explain enough of it to tell you why a lens focuses light onto a point. You get the idea.

Any scientist worth his salt will scoff at this- a chemist will bang on about the fact that nanotubes were only developed a decade ago and will revolutionise the world in another, a biologist will tell you about all the myriad of species we know next to nothing about, and the myriad more that we haven’t discovered yet, and a theoretical physicist will start quoting logical impossibilities and make you feel like a complete fool. But this is all, really, rather high-level science- the day-to-day stuff is all pretty much done. Right?

Well… it’s tempting to think so. But in reality all the scientists are pretty correct- Newton’s great ocean of truth remains very much a wild and unexplored place, and not just in all the nerdy places that nobody without 3 separate doctorates can understand. There are some things that everybody, from the lowliest man in the street to the cleverest scientists, can comprehend completely and not understand in the slightest.

Take, for instance, the case of Sugar the cat. Sugar was a part-Persian with a hip deformity who often got uncomfortable in cars. As such when her family moved house, they opted to leave her with a neighbour. After a couple of weeks, Sugar disappeared, before reappearing 14 months later… at her family’s new house. What makes this story even more remarkable? The fact that Silky’s owners had moved from California to Oklahoma, and that a cat with a severe hip problem had trekked 1500 miles, over 100 a month,  to a place she had never even seen. How did she manage it? Nobody has a sodding clue.

This isn’t the only story of long-distance cat return, although Sugar holds the distance record. But an ability to navigate that a lot of sat navs would be jealous of isn’t the only surprising oddity in the world of nature. Take leopards, for example. The most common, and yet hardest to find and possibly deadliest of ‘The Big Five’, everyone knows that they are born killers. Humans, by contrast, are in many respects born prey- we are slow over short distances, have no horns, claws, long teeth or other natural defences, are fairly poor at hiding and don’t even live in herds for safety in numbers. Especially vulnerable are, of course, babies and young children, who by animal standards take an enormously long time to even stand upright, let alone mature. So why exactly, in 1938, were a leopard and her cubs found with a near-blind human child who she had carried off as a baby five years ago. Even more remarkable was the superlative sense of smell the child had, being able to differentiate between different people and even objects with nothing more than a good sniff- which also reminds me of a video I saw a while ago of a blind Scottish boy who can tell what material something is made of and how far away it is (well enough to play basketball) simply by making a clicking sound with his mouth.

I’m not really sure what I’m trying to say in this post- I have a sneaking suspicion my subconscious simply wanted to give me an excuse to share some of the weirdest stories I have yet to see on Cracked.com. So, to round off, I’ll leave you with a final one. In 1984 a hole was found in a farm in Washington State, about 3 metres by 2 and around 60cm deep. 25 metres away, the three tons of grass-covered earth that had previously filled the hole was found- completely intact, in a single block. One person described it as looking like it had been cut away with ‘a gigantic cookie cutter’, but this failed to explain why all of the roots hanging off it were intact. There were no tracks or any distinguishing feature apart from a dribble of earth leading between hole and divot, and the closest thing anyone had to an explanation was to lamely point out that there had been a minor earthquake 20 miles ago a week beforehand.

When I invent a time machine, forget killing Hitler- the first thing I’m doing is going back to find out what the &*^% happened with that hole.