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.

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