Hacker News Reader

Comment by frozenport | Hacker News Reader

    The flow of time is an illusion, and I don’t know very many scientists and philosophers who would disagree with that, to be perfectly honest.

Oh humbug! I have seen many proofs that rely on time going in a particular direction. For example, when solving the wave equation for electromagnetics it it is customary to discard anticausal solutions.

View on HN

To be sure, we also typically throw away imaginary roots when factoring polynomials, since they'd represent nonphysical solutions. But the imaginary bits do come in handy for, well, nonphysical solutions, like measuring phase angle.

So while I tend to side with you that the philosophy bit is probably unnecessary, I would contend that there may be surprising usefulness in the nonsense solutions (or they're just nonsense; it's hard to tell looking at the future work that hasn't been done yet).

I'm not sure what he means by "flow of time" but I don't think he meant what you argued against. I think he's arguing against the notion that time is like some sort of continuum like a river, or like an axis on a map.

I got the same impression. People are assuming that by 'flow' he means uni-directional, as in the arrow of time. He is talking about the fact that 'flow' semantically implies something that moves, but movement itself requires time. So to say that time flows would be circular reasoning.

As I understood the article, he's neatly sidestepped most of those proofs with his definition of "the flow of time". He agrees that certain properties are associated with their direction along the time axis (e.g. entropy increase in the futureward direction, memories are only available of pastward events). Is suspect that he would also argue that throwing out the anti-causal solutions to the wave equation is nothing more that customary, and that Merlin and Chris Nolan would customarily discard causal solutions and keep only the anti-causal ones.

What was frustrating for me was that he didn't seem define "the flow of time". I would have defined it as the idea that the universe is not translation invariant along the axis measured by clocks. The truth of that statement is practically tautological, as he already agreed that clocks do measure intervals and that measurement inherently breaks the translation symmetry. Then again, cosmology isn't my field so maybe I'm missing something.

That's the direction of time, which is different from time having an actual "flow" or not.

Just like with control systems.

Reply on news.ycombinator.com