21 Sep Nature doesn’t allow measurements beyond a certain level of precision
The uncertainty principle is among the the most famous (and also probably most misunderstood) concepts in physics. It demonstrates that there is a fuzziness in nature, an elementary limit to the things we could know about the behaviors of quantum particles and, consequently, the tiniest scales of nature. Of these scales, the most we can hope for is to compute or calculate probabilities for where things are and just how they are going to behave. As opposed to Isaac Newton’s clockwork universe, wherein every thing follows clearly identifiable laws on how to move and forecast is simple once you know the starting conditions, the uncertainty principle enshrines an amount of fuzziness into quantum theory. Werner Heisenberg’s simple idea declares why atoms do not implode, how the sun is able to shine and, surprisingly, that the vacuum of space is not actually empty.
Heisenberg’s concept can also clarify a form of nuclear radiation known as alpha decay. Alpha particles are two protons and two neutrons discharged by some heavy nuclei, for instance uranium-238. Typically these are bound inside the heavy nucleus and would need plenty of energy to break the bonds holding them in place. However, because an alpha particle inside a nucleus possesses a really distinct velocity, its position is not so well-defined. This means that there is a small, yet non-zero, possibility that the particle could, at some point, find itself outside the nucleus, despite the fact that it technically does not have sufficient energy to escape. When this occurs – a process metaphorically known as “quantum tunneling” because the escaping particle has to somehow dig its way through an energy barrier that it cannot leap over – the alpha particle escapes and we see radioactivity. A similar quantum tunnelling process happens, in reverse, at the centre of our sun, where protons fuse together and release the energy that allows our star to shine. The temperatures at the core of the sun are not high enough for the protons to have enough energy to overcome their mutual electric repulsion. But, thanks to the uncertainty principle, they can tunnel their way through the energy barrier.