|The sculpture above is Salvador Dali’s “Dance of Time II” displayed in front of the ArtScience Museum at Marina Bay Sands in Singapore. (Inside Science)|
(ISNS) -- Almost nothing is more obvious than the fact that time flows from the past, which we remember, toward the future, which we don’t. Scientists and philosophers call this the psychological arrow of time. Hot coffee left on your desk cools down, and never heats up on its own, which reflects the thermodynamic arrow of time.
In a paper scheduled to appear this week in the journal Physical Review E, two physicists make the case that these two long-separate notions of time — one based on psychology and one based on thermodynamics — must always align.
The principles of thermodynamics show that large collections of particles, like the trillions upon trillions of liquid molecules in a coffee cup, always move toward more disorganized arrangements. For instance, hot water molecules clumped together in a cold room need a lot of organization, so warm drinks eventually cool to the surrounding temperature. Physicists say such disorganized arrangements have high entropy, whereas ordered arrangements have low entropy.
Good primer on the subject, and an attempt to bridge the philosophy with the physics. As I've stated to someone that's asked me about why backwards time travel isn't possible, my answer is it hasn't been observed in nature. We would see teacups or chandeliers "un-break" or waterfalls flow backwards. It would be quite visible and noticeable from the norm, I would think. If it were possible, we could have visitors from the future creating paradoxes that would wreck havoc to the timeline - someone would notice that as well.
Inside Science: Why Does Time Flow Forward? Gabriel Popkin, ISNS Contributor