

Physicists Demonstrate How Time Can Seem To Run Backward - chris_overseas
http://secondnexus.com/technology-and-innovation/physicists-demonstrate-how-time-can-seem-to-run-backward-and-the-future-can-affect-the-past/

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andresmanz
Ah, the headlines.

"Time moves forward; things exist in only one place at a time;"

I am not a physicist, so I'd like to ask one: Does it even make sense for time
to 'move'? I don't know, but I imagined time to be some kind of - for us
invisible - expansion of space (or... spacetime).

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Synaesthesia
It's more of a philosophy question, or metaphysics, asking where time does
objectively exist firstly and secondly, what it is. In physics we define it to
be something convenient which works for our models. Within these models time
can move forward and backward.

We may not even have a strict definition of time, and have to rely on our
intuition. For example there's no way to define what reality is.

My grandpa contends that time is just that which we ascribe to motion in
space, and if there were no motion, there would be no time.

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andresmanz
That already explains a lot, thank you very much! I've read so many different
definitions of time in physics - that was very confusing.

What your grandpa contends is exactly what I thought, too. I love the
simplicity of that thought. But after reading about the relativity of time, I
noticed that something must be missing. That's why I tried to imagine that
space expansion I mentioned. In the end, it doesn't really make sense, but
again the simplicity and thus the ease of imagining it is beautiful.

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JadeNB
How does this differ from the delayed-choice quantum eraser
([https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser](https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser)),
which also seems to exhibit this sort of paradoxical behaviour of "later
choices affect earlier events"?

