The h Bar

cowlinator

1:09 AM

Can I post harebrained theories here?

Secret

@enumaris You can have closed null curves and even closed space like curves

CTC must be timeline and the killing vector field vanishes or something

In particular, a spacetime with CTCs cannot be foliated into slices of space like hyperplanes

@cowlinator depends on what theory

rob

@cowlinator Harebrained theories tend to be met with a certain amount of eyerolling, which bothers some of the folks who produce them. But if you can tolerate that, then sure.

cowlinator

It's a theory, that I invented in my head, just now.

I'm just looking for sanity-check type of feedback

Secret

sure

cowlinator

Works such as "Natural Philosophy of Cause and Chance" imply that the notion of causality is metaphysically prior to the notions of time and space.

Additionally, there are multiple types of causes. Of interest:
"Sufficient cause" is defined as one effect which has many possible causes. (E.g. firing a flame thrower at a barn covered in gasoline). Trivial to predict the effect from the cause, difficult to discern the cause from the effect. I.e., easier to predict the future than discern the past.

rob

1:28 AM

What does it mean for time to expand?

Secret

1:39 AM

I think it is as hard to predict the past given some present event, e.g. figuring out what kind of interactions some particles in cosmic rays have experienced during its interstellar journey before it arrive to earth. In theory, any set of interactions that gives the observed momentum will be qualify as a possible cause, hence the cause of the momentum detected of some cosmic ray particle is a sufficient cause

In GR, locally for any observer, anything located at the past light cone can be potentially causally linked to the events at the observer, hence the past light cones defines all the sufficient causes for that event. Likewise, all the possible effects the event can produce is defined by its future light cone

@rob If I understood correctly, I think he is making use of the thermodynamic arrow of time, and equate the number of possible states and configuration a given (not necessary deterministic?) event can evolve to. He then hypothesise that the arrow of time points in the direction where the number of possible configurations the event can evolve to increases, and hence as entropy of the universe increases, time progresses forward

But I don't think that is true, as otherwise we will experimentally observe that e.g. probability of an electron being spin up will asymptotically approaches zero as the number of possible states it can end up increases with time

That is, a universe where the sample space of any given probabilistic or statistical event increases with time should let to the observable outcome that the probability of any event will become time dependent

which should be ruled out by the observation that e.g. we don't see the probability of an electron being spin up to be anything other than. 1/2 in 1900 vs in 2018

though this model may be easily amended by imposing some cutoff so that probability of getting some specific observable for a stationary quantum state remains unchanged with time

Secret

2:16 AM

cutoff in the length scale where it took place*

Physics Meta

0

Q: how can one identify a downvoter?

I was recently taken to task by another person here who fingered me as having downvoted one of his answers. He was right- but how is this possible? Until now, I was under the impression that a downvote did not carry with it the identity of the person who cast it. So... How can the recipient of a...

discussion

cowlinator

3:06 AM

@secret, you bring up some good points. Perhaps nothing can come of this theory, I will have to think about it.

By the way, while it is hard to predict the past at the quantum level, where equations tend to be time-symmetric, but at the macroscopic level, it is usually (but not always) easier to predict the past than the future. Every human has a fairly accurate memory, but makes less accurate predictions about the future. We have devices that can record past video or sound almost perfectly, but cannot do so with future video or sound. Etc.

Hmm, ok, I think I see what you mean. I don't think the increase in the number of whole-universal states over time would create additional possible spin states for each individual electron, would it? For any electron, the spin states would still be (up, down).

Secret

4:13 AM

I also think another place worthwhile to investigate is the philosophy as well the mechanism of recording a memory for any entity, as there is something highly time asymmetric about it

Rumplestillskin

5:44 AM

I have a question which may be trivial but my mind seems to think otherwise. If I am discussing the motion of a test particle (say a spacecraft) in a schwarzschild spacetime, how do I transfer to the reference frame of the Spacecraft? Is this the concept behind the tetrad formalism? If so, does anyone have a decent and readable document or reference?

Slereah

7:30 AM

@Rumplestillskin Fermi coordinates

Rumplestillskin

7:47 AM

@Slereah thanks! Do you know of any documents that discuss this in terms of solar system probes or spacecraft?

Slereah

8:24 AM

dunno

Secret

10:24 AM

nature.com/articles/s41598-018-33699-y

Daylight quantum key transfer. Looks like quantum systems are more noise tolerant now

Akash. B

12:20 PM

Hi

John Rennie

12:48 PM

I'm looking forward to lunch today:

ACuriousMind

1:14 PM

Breaking news: Time travellers are responsible for crying babies

2

@JohnRennie Are those...four lasanges at once?

John Rennie

2:03 PM

@ACuriousMind allegedly :-)

Secret

2:26 PM

@ACuriousMind This smbc actually highlight an important challenge in trying to detect any possible instance of retrocausality. An event whose cause is from the future is indistinguishable from the event happening, followed by the event that causes it to happen in the first place in the future

vzn

3:04 PM

lol smbc + time travelling + hitler counterfactuals + occams razor/ doncha luv cartoons o_O

@bolbteppa lol! p188 Hossenfelder lost in math compares string theory to the 1987 stephen king novel Tommyknockers ("an awful book")... hilarious! hows that for a science ref? (oops that ones missing from the index!) lots of other highlights, you guys gotta check it out, youre missing all the fun... has a huge cast of A-list characters... maybe she will be standup comedienne after quitting physics? eagerly looking fwd to it! now feel strong urge to blog on this asap! :) :o o_O :P

vzn

3:24 PM

@Secret thx much for your receptivity + ideas + actually reading the papers! there are 3 currently highly compartmentalized but apparently converging directions/ research programs in this area: QM madelung fluid afaik modelled as nonnewtonian elastic, Tenev + Horstemeyer spacetime fabric, Farnes spacetime fluid. unifying them this is now a GR + QM unification outline/ sketch. just remains for 21st century einstein to connect the dots™... :o o_O

Secret

Gaussian 16 quote:

> NOTHING RESEMBLES A NEW PHENOMENON AS MUCH AS A MISTAKE.

-- ENRICO FERMI (?)

Unfortunately the Journal of Experimental Errors (or something, I forgot its actual name) gone out of business

@vzn There might be something in common with them, and possibly something more interesting when dealing with the strong interacting regimes of those models, but I think they are still very far from approaching a TOE

vzn

@Secret oh yeah another aligned direction/ angle: Bush-Couder pilot wave hydrodynamics. and theres some fluid dynamics in string theory. it shows up in some Bell nonlocality analysis. much more in my blog. have cited most of it here over the yrs. etc... agreed a TOE does not seem to be in reach but neither does AGI yet progress is noticeable... the futures already here its just not evenly distributed™ —gibson

Aidan Rocke

Hello, does anybody here have a strong interest in statistical mechanics?

I have a very specific question: mathoverflow.net/questions/317192/…

Secret

> the futures already here its just not evenly distributed™ —gibson

hmm...

(jots into notebook and then think about how to manipulate the future field itself)

I knew nothing about that path integral, but it seems to be interesting thus I favourite that page for later

Captain Bohemian

"Man's sense of humor seems to be in inverse proportion to the gravity of his profession" (Mary Roberts Rinehart).

danielunderwood

3:43 PM

@ACuriousMind evidently I didn't cry much as a baby. Guess we know what that means now!

Avnish Kabaj

4:43 PM

@Blue Congrats on your diamond I just noticed

Abcd

whats a diamond?

is diamond = moderatorship? @Blue

Anonymous

@AvnishKabaj Heh, thanks :) It's been a month

Anonymous

@Abcd Yes, that's what they call it here ;)

Abcd

@Blue there's also a diamond beside your chat gravatar and name

Anonymous

@Abcd Yeah, site mods are chat mods too, by default

Anonymous

4:53 PM

Incidentally, I just received the t-shirt SE sent, a couple hours ago. It's way too large. Apparently, I chose the wrong size (XL). Mother said she can cut and alter it to my size, so there's some hope. :P

Anonymous

The hat's cool tho.

Avnish Kabaj

@Blue vao vao

Heh heh

I'll just get one printed

Anonymous

@AvnishKabaj Well, it's just a black t-shirt with the SE logo :P I'm looking forward to the site-specific swag we might get once the quantum computing site graduates

Anonymous

They gave the Chemistry guys designed beakers

Avnish Kabaj

Aaaages ago

When the site was really really alive

Anonymous

5:04 PM

46

Q: Chemistry — Top User Swag!

We want to congratulate and thank everyone that helped this site and community grow healthily into what they are today! If you can find your name among the top 72 users in the first two pages here, we have a surprise for you! Hoping to get a reaction with that joke... (｡ˇ艸ˇ) We want to se...

discussion

Anonymous

I don't remember Physics SE getting any swag

Anonymous

Or did they ?

Avnish Kabaj

@Blue they'll prolly just send you a quanta online

Anonymous

16

Q: Physics swag for top users

As a thank you for being awesome, if you have at least 1340 reputation (as of Feb 24) and are on page 1 or page 2 of … https://physics.stackexchange.com/users?tab=reputation&filter=all … we'll be sending you a little care package shortly: Physics Stack Exchange t-shirt in your size Physics St...

discussion

Avnish Kabaj

;)

Anonymous

5:07 PM

@AvnishKabaj lol

rob

Man, I had to win an election to get physics swag.

Anonymous

Swag's easy to get if you participate in one of those yearly MSE swag contests, I guess

Anonymous

Like the recent Cheese Overflow and watch

Transcript for