Alan Alda poses question in new contest for scientists: What is time?

[mindwalker_i]

36. Scientific American had a special issue on time

It was the year-end issue of 2011, and it discussed how time doesn't come out of any equation of physics - it always tends to cancel out completely. All events can be measured relative to physical events instead of time, kind of like we could barter instead of using money.

There's also reason to think that quantum mechanics transcends time. Measuring one particle that's entangled with another can affect its partner retroactively. A recent experiment by Anton Zellinger made measurements of two particles that were each entangled with another particle, which entangled the two measured particles and also entangled the two that had already been measured. By doing so, the two already-measured particles were shown to have correlated values.