ONE snowy day final 12 months, I trekked out of Vienna, Austria, winding my solution to one of many metropolis’s graveyards to go to the ultimate resting place of a large of Nineteenth-century physics. Ludwig Boltzmann’s tombstone options an imposing bust of the person, frowning down with a extreme expression. And there above him, in gold lettering, is his method for entropy. It have to be certainly one of just a few tombstones on the earth adorned with an equation.

I had come for a spot of contemplation as a result of I feel Boltzmann’s century-old concepts might assist remedy one of many trickiest issues in physics proper now: how quantum particles, which exist in a fuzzy cloud of doable states, give rise to the stable, well-defined world of snow, leaves, tombstones and every little thing else round us.

There have been many makes an attempt to elucidate this over time, together with the outlandish concept that the opposite quantum prospects play out in lots of different parallel universes or that they merely vanish. However my colleagues and I think the reply might lie with Boltzmann.

The idea he labored, known as thermodynamics, is centred on entropy, a measure of how disordered issues are. It explains how issues calm down, energy up and, crucially for our functions, combine. It covers on a regular basis goings-on, like milk mixing into espresso. But when we’re proper, its powers additionally prolong to the quantum realm. We predict these quantum prospects are by no means misplaced in any respect: as a substitute, they’re simply combined so completely into the cracks of actuality that we will’t see them. It that is…