Besides from being a series of popular first-person shooter video games, half-life is an important factor to consider in any applications of radioactivity. It seems quite a weird quantity at first glance; we usually talk about the lifespan of things, rather than half a lifespan. But as you will see, the ‘half-life’ is far more logical, because the lifespan of a radioactive substance is… well, infinite (theoretically).
Timekeeping. How could such a mighty power be exploited by a device as diminutive as a quartz wristwatch, to a remarkable degree of accuracy? Today we will break open one of said watches (through writing, of course), and see what lies inside.
Last week I explored the idea of time irreversibility in the universe. Our laws of physics are invariant over a T-transformation; whatever a particle does is not affected by whether it is moving forwards or backwards in time. Yet why do we still see an obvious ‘arrow of time’ in real life?
…which of the symmetries hold at all? The universe is a curious place and cosmologists endeavour to contain this curiosity into one theory. Or maybe two, if they’re unlucky.
Say you had a longing desire to flick on a switch connected by a very long wire to a light bulb far far away (because reasons). Would there be a delay before the bulb lit up? Could you run to the light bulb before the ‘electricity’ got there? No? How about if you flew in your private jet? We’ll see…