chat-log-two-time-dimensions

[11:48 PM] Goose: OK I finished the epilogue
[11:54 PM] cantordust: Mm, right, so now it's time to read the webpage
[11:54 PM] cantordust: https://www.gregegan.net/DICHRONAUTS/DICHRONAUTS.html
Dichronauts — Greg Egan
Illustrations for Dichronauts by Greg Egan
[11:54 PM] Goose: I am reading the webpage already. :stuck_out_tongue:
[11:54 PM] cantordust: There's basically an entire treatise :stuck_out_tongue:
[11:54 PM] Goose: I am going through it right now.
[11:54 PM] cantordust: man nice, he has the same thing for incandescence which is about SR/GR
[11:54 PM] cantordust: https://www.gregegan.net/INCANDESCENCE/Incandescence.html#CONTENTS
Incandescence — Greg Egan
Illustrations for Incandescence by Greg Egan
[11:54 PM] cantordust: Amazing, this might be the best way to learn SR lmao
[11:55 PM] Goose: Before anything, I am troubled by his treatment of the second dimension of time.
[11:57 PM] cantordust: how so
[11:58 PM] Goose: He treats the second dimension as another physical dimension, with physical manifestation.
[11:59 PM] Goose: The inhabitants of his world are free to move in the second time dimension, with a speed that they see fit.
[11:59 PM] Goose: However, speed along the time dimension isn't something we can control in our world. What reason have we to assume that it will be possible in this scenario?
[12:01 AM] cantordust: We can control speed along time? move a lot along space, you'll have very little through time.
[12:02 AM] Goose: You can stay still with respect to yourself, shut off your passage of distance, but can you shut off the passage of time?
[12:02 AM] Goose: Direction of time also has to do with entropy, and a "psychological arrow" also.
[12:03 AM] Goose: There's much more baggage attached to "time" than just "another dimension"
[12:03 AM] cantordust:
 You can stay still with respect to yourself, shut off your passage of distance, but can you shut off the passage of time?
Yeah, move like a photon?
[12:04 AM] Goose: I feel the geometry of SR and GR doesn't capture this "baggage".
[12:04 AM] cantordust: wdym
[12:04 AM] Goose:
Yeah, move like a photon?
Restrict our discussion to massive objects please, since I'm talking about human perception of time.
[12:05 AM] cantordust: It's unclear why I should do that. 1D space is also very "special" in ways that don't match 2D
[12:05 AM] Goose: Time flows in the direction in which entropy increases.
[12:06 AM] Goose: What I'm getting at is the fact that geometry [of SR/GR] doesn't talk of thermodynamics at all.
[12:06 AM] cantordust: And neither does GR :smile:
[12:07 AM] cantordust: I agree to the argument that yes, he doesn't describe how statmech works if that's you argument. But it's unclear you can infer this from his description of the world, locally?
[12:08 AM] cantordust: First of all you can't write dS/dt > 0 because time isn't one dimensional anymore
[12:09 AM] cantordust: so what's the correct rule? is it sum_{i in 2 3} dS/dt_i > 0? that's not covariant, so it should first of all be something like \sum_{i in 2,3} dS_i dS^i > 0 or something.
[12:10 AM] cantordust: I'd be interested to understand the ramifications of this, of course. But I don't see how this actually impacts the story in any way whatsoever
[12:10 AM] Goose: I don't know the correct rule. All I'm saying is that the u direction he speaks about seems to be more space-like rather than time-like
[12:10 AM] Goose: Of course it doesn't impact the story. I'm just disputing the claim that his world has "two directions" of time.
[12:11 AM] Goose: At best, you have one space direction whose sign is flipped in the metric.
[12:12 AM] cantordust: Why doesn't it have two directions of time
[12:12 AM] cantordust: I don't understand the objection
[12:12 AM] cantordust: you'll need to frame statmech differently
[12:12 AM] cantordust: I don't understand why it [supposedly] doesn't survive
[12:13 AM] cantordust: Also, isn't unifying thermodynamics with GR like, unsolved? xD because of the information paradox
[12:14 AM] Goose: I don't know the information paradox
[12:15 AM] cantordust: it's the thing where black holes supposedly manage to destroy information by being able to suck stuff up but only radiate heat out, thereby destroying information in the process is my ELI5 of this
[12:15 AM] Goose: Oh yeah.
[12:15 AM] Goose: There was another children's book about how Hawking radiation supposedly resolves this.
[12:16 AM] Goose: And you can reconstruct information from the emitted radiation.
[12:16 AM] Goose: But anyway, the third dimension doesn't feel like "time" more like a "weird space".
[12:17 AM] Goose: I'm not saying he should do better. I don't even know what better looks like.
[12:17 AM] cantordust:
But anyway, the third dimension doesn't feel like "time" more like a "weird space".
This is likely the correct perspective on time FWIW -_^
[12:18 AM] Goose:
This is likely the correct perspective on time FWIW -_^
hahahaha, fair enough
So it should be "two weird spaces" instead of "one weird space and 3 normal spaces" :stuck_out_tongue:
[12:18 AM] cantordust: yes :stuck_out_tongue:
[12:19 AM] Goose: In that case, I posit that his "second time" isn't as weird as his "first time"
[12:19 AM] Goose: It's weirder than normal space but not a weird as normal time.
[12:21 AM] cantordust: which one is "first" and which one is "second" xD
[12:22 AM] Goose: Anyway the point is moot we were going to talk about the geometry.
[12:22 AM] Goose:
which one is "first" and which one is "second" xD
First is the normal time t the second is the second time which he calls u
[12:23 AM] cantordust: ah, I have not read the page yet. Let me d so
[12:23 AM] cantordust: Now can I convince you to also read incandescence?
[12:23 AM] Goose: You don't need to convince me.
[12:23 AM] cantordust: :smile:
[12:24 AM] Goose: I was already going to read it. I'm incapabe of not binging stuff.
[12:24 AM] cantordust: xD
[12:25 AM] cantordust: Nice, this should give us enough material to get more solid on SR and GR
[12:25 AM] Goose: I hope. Let's see.
[12:25 AM] cantordust: I think actually writing some sort of simulation for 1+1, 1+2 and 2+1 will be very useful, to get a feeling for WTF it means it have "two space axes" and "two time axes"
[12:27 AM] Goose: That's the thing. The way he's described it it's not "two time axes" it's more like "one time and one weird stretchy space like axis"
[12:29 AM] cantordust: Hm, well, I'll read his explanations I suppose :smile:
[12:31 AM] cantordust: I dig all of his work TBH
[12:31 AM] cantordust: I really enjoyed permutation city, as well as Diaspora
[12:32 AM] cantordust: I'm now going to read his orthogonal trilogy
[12:32 AM] cantordust: see where that takes me.
[12:44 AM] cantordust: What are you up to now?
[12:48 AM] Goose: playing a game
[1:26 AM] Goose: https://www.reddit.com/r/math/comments/iklhxa/rendering_hyperbolic_spaces_hyperbolica_devlog_3/

I want to understand how he plotted the vertical dimension. He does some insane wrap around stuff for that.
reddit
r/math - Rendering Hyperbolic Spaces - Hyperbolica Devlog #3
173 votes and 3 comments so far on Reddit

[4:02 PM] cantordust:

[4:02 PM] cantordust: This is from his book"clockwork rocket"
[4:03 PM] cantordust: I'm not sure what funky stuff is going on with the physics yet. If I've inferred correctly, this universe doesn't have the speed of light as a constant barrier, and there's some odd stuff going on with energy conservation
[4:04 PM] Goose: Completely possible. But the mere happenstance of history renders one dimension "different" from the rest, no
This is from his book"clockwork rocket"
[4:04 PM] Goose:
I'm not sure what funky stuff is going on with the physics yet. If I've inferred correctly, this universe doesn't have the speed of light as a constant barrier, and there's some odd stuff going on with energy conservation
I'll see if I can get to it soon
[4:06 PM] cantordust:
Completely possible. But the mere happenstance of history renders one dimension "different" from the rest, no
Seems unclear to me. I mean, perhaps in the observable universe, there's more "stuff" along the z axis [I have no idea if this is the case]. Does that make this particular axis somehow "special"?
[4:09 PM] Goose: "direction of time" isn't just a geometrical direction. The word "time" carries with it the baggage of increasing entropy and what not. Treating it as "just another space direction with opposite metric sign" leads to extensions like the second time axis in Dichronaurs. Geometrically everything works out, but psychologically it doesn't feel like time.
[4:10 PM] Goose: To answer your question, indeed it makes that particular direction somewhat special. I wouldn't put it on the same degree of special as "time direction" but it's definitely somewhat special.
[4:15 PM] cantordust: Mm, are you reading incandescence now?
[4:16 PM] Goose: Not yet. First I have to finish that explanation of the dichronauts world.