from Hacker News

Arrows of Time

by mayankkaizen on 12/9/23, 8:53 AM with 16 comments

• by lisper on 12/10/23, 12:13 PM

  > In an influential [2008] paper, Noah Linden, Sandu Popescu, Tony Short and Andreas Winter argued that the arrow of time can be explained in terms of quantum mechanical entanglement. As a physical system becomes entangled with its surroundings, it moves closer to equilibrium — and this one-way evolution determines time’s arrow.

  There is an alternative, much simpler way of looking at it that dates back to an overlooked 1996 paper by Nicolas Cerf and Christof Adami: the arrow of time depends on entanglement because that's the only way to get classical correlations (i.e. memories) out of quantum mechanics.

  https://blog.rongarret.info/2014/09/are-parallel-universes-r...

  https://blog.rongarret.info/2014/10/parallel-universes-and-a...

  You can arrive at the same conclusion relying solely on the theory of decoherence, which can be traced back as early as 1970:

  https://ui.adsabs.harvard.edu/abs/1970FoPh....1...69Z

• by chriscjcj on 12/10/23, 5:08 PM

  The title reminds me of the old joke...

  "Time flies like an arrow. Fruit flies like a banana."

• by 082349872349872 on 12/10/23, 1:53 PM

  see also "Arrow of Entropic Time": https://www.youtube.com/watch?v=i6rVHr6OwjI

  (or should that be "ǝɯᴉʇ ɔᴉdoɹʇuǝ ɟo ʍoɹɹɐ"?)

• by 1010s1011 on 12/10/23, 11:00 AM

  They completely forget one of the most famous historical historical clocks which preceded the Chinese mechanical clock (1090CE) they listed by about 280 years (807CE).

  It was gifted to Charlemagne, the Holy Roman Emperor, by Harūn al-Rashīd: https://muslimheritage.com/baghdad-clock/

• by daveguy on 12/10/23, 7:16 PM

  I'm a little disappointed that an article about our understanding of time across history didn't include the marine chronometer. It was a major breakthrough for nautical navigation in the 1700s. It allowed precise longitude determination long before GPS. Prior to the marine chronometer latitude could be precisely determined with celestial navigation, but longitudinal skew due to earth's rotation could not be compensated for without precise timekeeping.

  https://en.m.wikipedia.org/wiki/Marine_chronometer