Mysteries of time, and the multiverse | Hacker News Reader

Mysteries of time, and the multiverse

latimes.com

10 pointsnickb13 comments

The fact that you can turn eggs into omelets but not vice versa is a thing we know from our kitchens.

Unless you feed a hen nothing but omelets. Am I right?

What about the hen's mother?

Given a sufficiently efficient hen, you could feed her her own eggs.

But wouldn't you have to feed omelets to the hen's mother also? Otherwise the hen couldn't have been born. And the hen's mother's mother, and mother's mother's mother, and so on, leading back from the final egg.

edit: on second thought, this is probably too much philosophizing.

A hen is a machine which can turn food (including omelets) into eggs. It doesn't matter where the hen came from. The point is one can build a machine to do this.

A hen interpreter?

Time cannot change by definition. Nothing can move in spacetime for the same reason. This is why the late Sir Karl Popper (of falsifiability fame) once compared spacetime to Parmenides' block universe and called it "Eintein's block universe in which nothing ever happens". (Source: Conjectures and Refutations).

In his textbook, "Relativity From A to B", renown relativity expert Robert Geroch wrote, "There is no dynamics within space-time itself: nothing ever moves therein; nothing happens; nothing changes." Very few physicists know this but it's the truth, a nasty little truth for some, but the truth nonetheless.

In conclusion, any talk of time travel in any direction (forward or backward) is pure crackpottery. There is only the NOW, the ever changing present. Don't mod me down because you have a different opinion. Incessant propaganda and sci-fi movies like Star-Trek have duped a lot of people. Just think about it and figure it out on your own.

Nothing can move in spacetime.

You're not explaining that very well. Yes, classic relativity is a deterministic theory which doesn't have a time arrow. You can look at it as a single, static universe defined as the sum of all moments. But that's neither here nor there. Classic relativity is, strictly speaking, wrong: the real universe is, as far as we understand, provably non-deterministic.

And in any case, it has nothing to do with this article, which is about the time arrow defined by entropy.

I am not sure exactly what you explained. First off, relativity, like Newtonian mechanics, is a classical physics theory. I am not aware of any such thing as non-classical relativity. So why even say classical relativity? At the very least, it is redundant.

Second, of course the universe is probabilistic, a fact that falsifies both relativity and Newtonian physics.

Third, the universe is probabilistic precisely because time cannot change. Why? Because, since time is not a variable and is thus non-existent, the universe cannot calculate precise temporal durations. Thus, in order to properly conserve energy, it is forced to use the next best thing: probability.

Fourth, this has everything to do with article since entropy, as explained in the text books, assumes the passage of time and thus a time direction or arrow. Since time is abstract, it follows that an arrow of time is imaginary. As a result, it makes perfect sense that one cannot reverse entropy. Or anything else, for that matter.

The purpose of my comment was to get people to think and to stop accepting everything they hear on face value. If time cannot change, which is trivially shown to be true (changing time is an oxymoron because it is circular), then all the so-called time-travel conjectures by famous physicists like Kip Thorne, Stephen Hawking, David Deutsch, and many others, are pure crackpottery.

"nothing ever moves" does not mean that no blocks in the block universe are related in such a way that we can reasonably say the same object is in both. and if the same object is in two or more blocks of the universe, which are different times, then it exists at different times, or in other words travels through time. this doesn't prove traveling back in time, or skipping forward in time is possible, but the concept does make sense in a block universe, and the standard time travel via time passing still works fine.

But +1 for quoting Popper.

Yes, there's no "time outside time", but maybe there are loops (closed timelike paths) inside the block universe.

I don't think you get it. A block universe in which nothing happens cannot possibly exist since it is clearly falsified. We observe change, do we not? So speaking of loops within a block universe is like arguing about how many angels can dance on the head of a pin. Is it me, or do other people go out of their way to be illogical?

Change can be viewed as a sequence of distinct immutable observer-moments, like frames in a movie, and nothing forbids them to form a loop.

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