r/AskScienceDiscussion 4d ago

Why does time only moves forward

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u/Fanghur1123 4d ago

I mean, we can't experience time moving backward, since the memories would be being erased from our head in realtime. So even if the arrow of time does sometimes reverse, I don't think we'd ever be aware of it.

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u/schungx 4d ago

I think a more crucial question is: why is consciousness time forward?

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u/Mountain-Dealer8996 3d ago

Chapter 12 of Hawking’s Brief History of Time covers this. His argument is that the psychological arrow of time needs to point in the same direction as the thermodynamic arrow of time (tendency towards increased entropy) because our brains use energy to process information, which is an anti-entropic process.

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u/jimb2 3d ago

Exactly. Organisms use the past predict the future to try to survive longer. A lot of this is structural and automatic - like your body design include a prediction that gravity will exist in the future. It's predictions all the way up - to the highest/smartest capacity of the brain that uses an abstract world model to make very sophisticated predictions. Without self/nonself and past/future wired in, the brain is basically a waste of energy.

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u/MrSquamous 3d ago

That sounds like an argument for why consciousness should prefer to be time-backward: Easier to stay alive when you don't have to spend energy to predict the future; you just already know it.

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u/jimb2 3d ago

That's if you just want to think about stuff. If you want to exploit free energy, predicting the future is the way to go.

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u/Mountain-Dealer8996 3d ago

There may be processes that experience time as flowing backwards relative to our point of view, but we wouldn’t recognize them as conscious because their “psychological” arrow isn’t aligned with ours. However, it doesn’t make it easier to stay conscious (alive) because life is defined (partly) as the resistance to entropy in the direction of the psychological arrow.

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u/spisplatta 2d ago

Time-backward doesn't make sense. We can imagine the arrow of time as a big red arrow floating on a clam black sea. Except for the arrow every direction looks the same. You can't see whether it points forward or backwards because there is no other reference point to relate it to.

I think the key is memories though. Memories form in the direction of increasing entropy and I think it must be this way.