The h Bar - 2019-10-17

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Novalium Company

3:42 AM

In QM, in the double slit experiment, will the wave function collapse if we put a detector, the detector detects, but when make sure the information is deleted?

What if we use an animal?

Despite all attempts to trick the system, eventually we always get to the human observation? (or potential to do so?)

4:33 AM

@NovaliumCompany The problem isn't that the universe doesn't want you knowing about the particle. It's that any method to learn about the particle will interact with it, and therefore alter it in some way

Try to see it? The light particle interacted with it.

In the end there's no way to learn about it's "undisturbed state" without disturbing it, which results in the wavefunction collapse

3 hours later…

7:42 AM

0

Q: Erasing comments for questionable reasons

The following relates to this answer written by Emilio Pisanty: Is there a magnetic attraction between two parallel electron beams? Originally, the said answer was referring to a chapter that did not exist in the most recent edition (3rd) of the book. Naturally, I commented about it, asking for...

discussion comments

1 hour later…

8:50 AM

Delayed-choice quantum eraser

A delayed-choice quantum eraser experiment, first performed by Yoon-Ho Kim, R. Yu, S. P. Kulik, Y. H. Shih and Marlan O. Scully, and reported in early 1999, is an elaboration on the quantum eraser experiment that incorporates concepts considered in Wheeler's delayed-choice experiment. The experiment was designed to investigate peculiar consequences of the well-known double-slit experiment in quantum mechanics, as well as the consequences of quantum entanglement. The delayed-choice quantum eraser experiment investigates a paradox. If a photon manifests itself as though it had come by a single path...

9:03 AM

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Q: Should we flag all comments that are no longer needed?

Parent question: Erasing comments for questionable reasons I am trying to get a general policy. My initial concern was about comments to answers that asked for details and/or corrections, and were erased as soon as the answer was updated accordingly. There are numerous comments all over SE that...

discussion comments

1 hour later…

10:23 AM

Heyyyy

I looked up my emails for my site

user image

It's John Manchak!

I need to add some captcha on my site's message form because there are way too many spams

"Hey Slereah, don't you allow comments on your blog? I do on my blog:

http://physicsdetective.com/

I wanted to leave you a comment pointing out that there's no travelling around a closed timelike curve. Wheeler conflated a circle with a cycle. Spacetime models space at all times. It's an abstract thing, not something real. The map is not the territory.

Regards
John Duffield"

DUFFIEEEEELD

10:43 AM

Oh god

Duffield sent me several messages

"LOL, that h-bar is a laugh. I was born 13 months after Einstein died."

11:43 AM

@Slereah Is he trying to imply that he is Einstein reincarnated?

It is certainly suspiscious

Obviously Whoopi Goldberg is Einstein reincarnated. So he can't be

That's why she was always center square on hollywood squares. She was that smart

12:10 PM

I was originally not going to post this, but seeing the JD message make me facepalm so much that I decided to just unleash a logic bomb to h bar

user image

Meanwhile, in a double irony, I think I started to have some idea what time travel in presentism will be like

All that is needed is two spacelike events to be classically correlated, and then the memory of the observer encodes that event in such a way so that when reading out the history recorded by the person, you recover a structure of events that arranged like a CTC

12:45 PM

:52170414 The message form on my website

"Wheeler conflated a circle with a cycle."

What does he mean by this

Also Wheeler was a professor here

There's a big picture of him in the physics department

@RyanUnger I'm more curious what he means by "The map is not the territory". I get that I don't walk on the map to get to my destination, but if there's a trail on the map I expect to be able to walk on that trail

Wheeler is kind of a weird GR figure

He seems to be super huge in GR but I can't think of that many things attributed to him?

all figures in GR are weird

@Jim I think he means local coordinates are not the whole manifold...

12:49 PM

Not wrong

But does he actually know what a manifold is

I'm not sure Duffield actually means something when he says such things

Next thing you know, he'll be pushing the time cube idea on all of us

time cube?

timecube.2enp.com

12:53 PM

Harmonic Cube

oh no

do yourself a favour and don't read the whole thing. Scroll to a random place and read a line or something

scrolls

oh jesus

(Dr Gene Ray, Cubic and Wisest Human, depicted in image above)

there's a wikipedia page

@Jim actually

"Religious/academic taught singularity is unicorn as 1 burrito"

Duffield just means that our understanding of physics is precisely that

it's not a perfect description of reality

I think Duffield says lots of reasonable things

They just dont fit together too well

@RyanUnger I think we're aware of that. But I don't get how that makes travel around CTCs impossible

12:57 PM

because CTCs are an artifact of the theory, not a part of reality

we may not live in a spacetime with them, but I fail to see how they'd be untraversable were we in the proper spacetime

does jd believe in quantum mechanics?

maybe he's thinking of some kind of instability mechanism

It is hard to say what JD believes

it is not greatly coherent

probably yes, but I don't want to speak for him

too bad the mods keep banning him from here

1:00 PM

Well I mean

He has a website

if you want to talk to him you can go there

@RyanUnger really? I didn't notice that. CTCs make great toy models for a variety of things in GR

Also since you are only interested in math I'm not sure the whole wormhole/CTC issue is greatly relevent

lol well one of them comes to se so ill retract that

It's just a manifold that isn't simply connected

but its true to some extent

1:01 PM

Well it's not a super useful field of GR, certainly

As far as experiments go

the real issues in GR are not due to topology

But overall most of GR isn't super useful

^ that

no one is claiming to do useful work

2

You could probably do most of the experimental GR work with linearized gravity

1:03 PM

@RyanUnger That should be the physicists creed

or parametrized post newtonian formalism

non sequitor rant: university tells me my password has expired, fine

but now apparently your university password has to be 16 characters long

and...srsly?

such is the modern world

just use a password manager

or write it on your phone

1:21 PM

@Semiclassical At work, there's a system where you have to change the password when it expires. When you go to change it, there are two boxes "Old Password" and "New Password"; there is no "New Password (repeated)" or similar box to fill in. When you enter an old and new password, it just spits up the error "the passwords do not match"... even though the old and new password aren't supposed to match

Its kinda a crappy old system so IT seems happy to just reset the PW for me when it expires

1:33 PM

@Semiclassical well, be thankful that you're not in UCL

they have an entropy meter that determines how long your password will be valid for

heh

I work in the PRIVATE SECTOR and they are super big on security???

@EmilioPisanty cf above

The company's website just assigns new passwords to you periodically

@Slereah ugh

mandatory xkcd reference:

user image

Now that Manchak said he likes my article on non-Hausdorff manifolds I guess I have to finish it

@Slereah How dare he be interested in what you did! Honestly, some people don't take the time to consider other people's schedules when they just go around liking physics works.

1:52 PM

It is very much appreciated, but now I am embarrassed by how terribly unfinished it is!

2:45 PM

@Jim but if everyone used random collections of words, it'd be much easier to crack

@RyanUnger different languages?

1 hour later…

4:13 PM

@RyanUnger There are about 59 million words in the English OED. If everyone uses a random collection of 4 words, the search space is 59 million to the power of 4, which is larger than 2^103, so that's still much better than a short gibberish password

@ACuriousMind i don't think your average individual knows 59 million words

If we pessimistically reduce that to the average passive vocabulary of English speakers of 40000 words, we still get about 2^61

If the attacker is only going for low hanging fruit and only checks for the 1000 most common words, we're still at 2^39

I.e. the computation Randall makes there already accounts for the "passwords are only made of words" attacks, since his 2^44 isn't far off from this

4:31 PM

so is there any point to changing passwords every 3 months

because my uni requires that and it is starting to seem very stupid

@SirCumference Well sure

But it also has downsides

honestly when there are a lot of password changes and the passwords have to be very complicated, I just use a lot of "I have forgotten my passwords"

@Slereah i mean presumably it's in case my password was cracked already, so that it wouldn't work anymore

but if it were cracked already i'd probably see some red flags

and if it weren't cracked then there's no benefit to changing my password frequently

I just use the Spaceballs password

Spaceballs 12345

4:50 PM

twitter.com/SwiftOnSecurity/status/1040621143181459458

This is how you do security

Take a computer that runs infinitely long time

and make a 0 to 1 at the current tape position if the input have a maximum

It turns out it is extremely hard to tell whether the input is finite without referencing the natural numbers

(at least philosophically that is, I don't know how you compute on infinitely non stopping turing machines)

@Slereah : The pointy-haired boss in one Dilbert strip uses 5 asterisks * * * * * as password inspired by how the password box looks like before typing :D

To be fair, hard to guess!

But easy to crack

5:20 PM

@Slereah well, it appears 27k times in Pwned Passwords, so I wouldn't consider it really safe

Apparently fartbum is also unsuitable

"This password has been seen 42 times before"

monkeylove has been used 4332 times

Damn

It's hard to find an appropriate random combination of words

correcthorsebatterystaple has been used 120 times

showmethemoney 3,393 times

where'sthebeef is available, though

if you need a new password

5:52 PM

RicciFlow is good

@ACuriousMind 59 million?

I know at most 2000 words

@RyanUnger Then you would sound like this:

user image

6:08 PM

I only know one word

So I use this instead

isotropic.org/papers/chicken.pdf

6:40 PM

@Loong what is this

@RyanUnger xkcd.com/thing-explainer

I said 2000

I think that’s about right

3 hours later…

10:07 PM

user image

hmmm

So the idea would be to stay in the age before science?

10:35 PM

@Slereah How'd ya respond

I did not

11:03 PM

To me that reads like total satire, but I would sadly believe if it's not.

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