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I'm not in UK so the video is restricted for me.
Physicist Jim Al-Khalili routinely deals with the strangest subject in all of science - quantum physics, the astonishing and perplexing theory of sub-atomic particles. But now he's turning his attention to the world of nature. Can quantum mechanics explain the greatest mysteries in biology?His first encounter is with the robin. This familiar little bird turns out to navigate using one of the most bizarre effects in physics - quantum entanglement, a process which seems to defy common sense. Even Albert Einstein himself could not believe it. Jim finds that even the most personal of human experiences - our sense of smell - is touched by ethereal quantum vibrations. According to the latest experiments, it seems that our quantum noses are listening to smells. Jim then discovers that the most famous law of quantum physics - the uncertainty principle - is obeyed by plants and trees as they capture sunlight during the vital process of photosynthesis.Finally, Jim asks if quantum physics might play a role in evolution. Could the strange laws of the sub-atomic world, which allow objects to tunnel through impassable barriers in defiance of common sense, effect the mechanism by which living species evolve?
What is Quantum Physics?That's an easy one: it's the science of things so small that the quantum nature of reality has an effect. Quantum means 'discrete amount' or 'portion'. Max Planck discovered in 1900 that you couldn't get smaller than a certain minimum amount of anything. This minimum amount is now called the Planck unit.Why is it weird?Niels Bohr, the father of the orthodox 'Copenhagen Interpretation' of quantum physics once said, "Anyone who is not shocked by quantum theory has not understood it".To understand the weirdness completely, you just need to know about three experiments: Light Bulb, Two Slits, Schroedinger's Cat.Two SlitsThe simplest experiment to demonstrate quantum weirdness involves shining a light through two parallel slits and looking at the screen. It can be shown that a single photon (particle of light) can interfere with itself, as if it travelled through both slits at once.Light BulbImagine a light bulb filament gives out a photon, seemingly in a random direction. Erwin Schroedinger came up with a nine-letter-long equation that correctly predicts the chances of finding that photon at any given point. He envisaged a kind of wave, like a ripple from a pebble dropped into a pond, spreading out from the filament. Once you look at the photon, this 'wavefunction' collapses into the single point at which the photon really is.Schroedinger's CatIn this experiment, we take your pet cat and put it in a box with a bottle of cyanide. We rig it up so that a detector looks at an isolated electron and determines whether it is 'spin up' or 'spin down' (it can have either characteristic, seemingly at random). If it is 'spin up', then the bottle is opened and the cat gets it. Ten minutes later we open the box and see if the cat is alive or dead. The question is: what state is the cat in between the detector being activated and you opening the box. Nobody has actually done this experiment (to my knowledge) but it does show up a paradox that arises in certain interpretations. If you dare to think about it (you're not really supposed to), you have to believe one of the following things:
It may come as a surprise to learn that there is a way to make sense of all three of these seemingly paradoxical features of quantum mechanics. However, there is, of course, a price to pay for that solution: a paradigm change as startling as the one that accompanied Einstein's theory of relativity — which told us, despite our intuitions, that there is no such thing as absolute space or time. Quantum physics requires that we "think outside the box," and that box turns out to be space-time itself. The message of quantum physics is that not only is there no absolute space or time, but that reality extends beyond space-time. Metaphorically speaking, space-time is just the "tip of the iceberg": Below the surface is a vast, unseen world of possibility. And it is that vast, unseen world that is described by quantum physics.