The h Bar

Nehal Samee

1:00 PM

@Secret .. I divided restoring force by mass of ball to get acceleration ... Then I used $v=\sqrt{2(a+g)h}$ ...

Is it logical...?

King Tut

can someone tell me definite ways to learn physics starting from end of school, irrespective of field

Slereah

Go back to school

is the first step

King Tut

The order to follow

Nehal Samee

@KingTut ... Read books , solve problems , watch lectures of Walter Lewin ...

King Tut

@slereah actually i am in school and going out of the school in some years (3-4)

Slereah

1:05 PM

a good step

Be cool stay in school

King Tut

@Nehal thanks very helpful, but what order to follow

@Slereah Not funny but you get points for the rhyme

Slereah

Well what do you want to learn

Secret

@NehalSamee The net force that propell the ball donwards should be 3k+mg=ma. Thus a=3k/m+g. Thus v=sqrt(2ah) and h=20+3. You cannot simply add the two accelerations together because the restoring force has no dependence on the mass of the ball

King Tut

@Slereah many things like relativity and quantum mechanics, i watch movies on them

I mean documentry

Sebastiano

Good morning to everybody.

Slereah

1:10 PM

Are you sure you actually want to learn such things

Sebastiano

I have posted this question

1

Q: Orthogonality relationship of electric field and electrical potential of two parallel plates

We known that the potential generated by a charge pointwise $q$ is $V(r) = kq/r $ and the equipotential surfaces (in 3D) are spheres centered in the charge with $r\geq 0$ where $r=d(O,P)$, i.e. the distance between the origin and a generic point $P$. In fact if we are in space, where an orthono...

Slereah

If you only know them from pop science documentaries, odds are good this has little in common with how you'll like doing actual QM

Sebastiano

I hope to have some answers. Best regards to everybody

King Tut

@Slereah is it hard/boring

Slereah

Quite so

Secret

1:12 PM

quantum doing proper is a lot harder than the popsci stuff, but a lot more fun and fullfilling

(that might be because I like to do linear algebra (as long there isn't too many nasty looking numbers))

GR meanwhile, is a lot more unintuitive

SR is still ok in that you can use diagrams to guide you while you perform the lorentz transformations

O, and don't touch QFT until you knew quantum back to forth, don't make the same mistake as I do

King Tut

Yes I also played a game about the special relativity called velocity raptors which also was cool

@Secret Thanks so there is a definite order, so how to start

Slereah

You can try 't Hooft's list

staff.science.uu.nl/~hooft101/theorist.html

Secret

I am bad at book recommendations because I still don't have time to read a proper QM book, Slereah and other QM guys will fill you in the reference list (sniped)

King Tut

So we need to study all this (or most of it)??

Slereah

It depends what you want to do, but the first 8 parts or so, yes

Nehal Samee

1:20 PM

You start from basics ... Like read easy books ... Don't be ashamed of starting from the root level ... Ask yourself WHY?. And take help from the experts here ...

@KingTut...

@Secret ... That's what I did ... Look that the velocity then is larger than that you found with energy conservation ...

King Tut

Hm yes true @Nehal what question are you doing let me also try it

@Slereah thank for book list and order, but many links are not working there is there a work around

Nehal Samee

@KingTut ...spring is hanging at 20m height from the ground . A ball of mass 0.2kg is shot towards the spring with velocity 49m/s such that extension of spring is 3m . What will be the rebound velocity of ball on the ground ?

@Secret ...?

King Tut

@nehal extension or compression

Nehal Samee

It's compressed 3m ...

King Tut

@nehal is ground hard I mean is heat lost in the ground

Nehal Samee

1:29 PM

Nothing regarding heat lost in ground ...It's free from all sorts of imprecations...

@Secret ..

physics.stackexchange.com/questions/394208/… ..

This is one which is easy considering energy ... But difficult with force (at least for.me )...

Secret

The only thing I can see that can go wrong is that the restoring force is being applied in increments as the spring extends, thus that might explain why the restoring force < kx

otherwise I have no idea where else the energy can go since that question has zero loss pathways

King Tut

is my equation correct:

$-mgh-\frac{x_{spr}^2 k}{2}=-\frac{mv^2}{2}$

h is distance from lower end of spring from where ball throws

Secret

actually, the question never said at what height is the ball thrown towards the spring

Sir Cumference

@Secret Which looks better, ad #1 or ad #2

Secret

which is why it is kinda confusing

King Tut

1:38 PM

@Sir ad #1 because #2 is too much

Sir Cumference

@KingTut K good, I thought so

Secret

@SirCumference if you want a high res after it is automatically resized by the ad box, I will go for #2

Sir Cumference

@Secret Both are high res, I just don't have the high res #1 on me

King Tut

but both are good

Secret

oops sorry , I did not noticed the extra telescope

King Tut

1:39 PM

@sir where are u putting the ad

Sir Cumference

7

A: Community Promotion Ads - 2018

Secret

Yeah, I will still go with #2, cause that telescope adds some "personality" that it is astro SE

Slereah

@SirCumference Telescope looks out of place

Sir Cumference

Hmm, tough choice

Slereah

The letter A has a gradient of color around it

while the telescope has a hard boundary

Sir Cumference

1:40 PM

Making the A a tripod seemed like a good idea at the time, but I'm worried it's too much

@Slereah I could fix that up, but what do you think of the telescope being there?

King Tut

Yes @sir text has a glow

Lozansky

I prefer #1

Slereah

I have no strong feeling one way or the other

also astronomy is lame

King Tut

@secret so is the equatino correct

I mean we dont know the h apart from it

Sir Cumference

@Slereah Astronomy is cool

It's like the only good application of physics

Secret

1:43 PM

@KingTut Yeah, I used the exact same equation as yours

King Tut

@sir yeah I have made telescope using lens but its very far from it

Secret

@SirCumference Hawking: Always be curious and look towards the stars

Astronomy may not always feed back to society quickly, like particle physics, but the curiosity of the universe keep us humans from destroying ourselves. Even if all religions were to die out tomorrow, our curiosity of the universe keep us together and remind us the importance to wonder and be unified

Slereah

Astronomy is actually the one field of physics that has been used by society for thousands of years

it's like the one field of physics that has consistently been studied and applied since the neolithic

Sir Cumference

Well, it was mostly astrology before ~Galileo

Slereah

Plz

Navigation

King Tut

1:46 PM

@sir no

Slereah

and timekeeping

since TIMES IMMEMORIAL

Sir Cumference

Well yeah, but not useful stuff

King Tut

xD

Sir Cumference

Like knowing about the solar system, the universe, etc.

Slereah

Not as useful as ASTROLOGY, certainly

What do you think Kepler did for money

Sir Cumference

1:47 PM

I said ~Galileo

± 200 years

Secret

Aboriginals have been using the night sky and the constellations to navigate the continent for centuries

Slereah

And also Galileo

King Tut

Is it true that kepler was not that good but brahe was good person

Slereah

The big money in physics was 1) navigation 2) timekeeping 3) ballistics

Sir Cumference

@Secret Navigation is useless

Slereah

1:48 PM

Those were the big applied physics fields

though ballistics is a bit more recent

Not much use for it before the catapult

and especially cannons

Emilio Pisanty

@Akash.B for clarity: "I asked you a question" does not entitle you, or anyone, to a response. If the people currently in chat are not interested in answering the question you asked, then you just join the long list of people, high- and low-rep alike, who've asked questions here that others have not been interested in at the time.

John Duffield

@BalarkaSen : there's a lot of loony material out there. The trouble is some people don't realise it's loony material. They take it seriously, and it's very difficulty to get them to take a step back and take a long hard look at it.

Secret

seeing JD reminds me... digs back to the notebook

Emilio Pisanty

That said, though, the chances improve if your answer can't be immediately resolved with a google search (so e.g. googling your exact questions brings this up on the first page of results. If you ask a question that's that unresearched, you have very little grounds indeed to complain that nobody answered it.

King Tut

@secret noo our equation is wrong then

John Duffield

2:04 PM

Don't you just love things like this: "Eventually Susskind — in a discovery that shocked even him — realized (with Gerard ’t Hooft) that all the information that fell down the hole was actually trapped on the black hole’s two-dimensional event horizon".

When I read things like that, I have a read of things like this and this‌.

Slereah

I hope it doesn't hit too close to home

John Duffield

It doesn't, because there's a supreme irony to it. See this:

"Matter travels onwards to the singularity at r = 0, and becomes invisible to the outside observer. All this is elementary exercise, and not in doubt by any serious researcher".

It doesn't. I am serious about that.

Slereah

2:30 PM

"They simply copy and paste text & equations they have found in 19th century literature, introductory physics textbooks, or the web, none of which they understand well enough to pass a test in school."

uncanny

John Duffield

See 't Hooft's website. His lecture notes on the quantum black hole are worth a glance. On slide 13 he refers to Shapiro drag, on slide 14 he refers to Shapiro shift.

But Houston, we have a problem:

Shapiro time delay

The Shapiro time delay effect, or gravitational time delay effect, is one of the four classic solar system tests of general relativity. Radar signals passing near a massive object take slightly longer to travel to a target and longer to return than they would if the mass of the object were not present. The time delay is caused by spacetime dilation which increases the path length. In an article entitled Fourth Test of General Relativity, Shapiro wrote: Because, according to the general theory, the speed of a light wave depends on the strength of the gravitational potential along its path, these...

@Slereah : but don't you just love this: "They find some support from ancient publications by famous physicists; in the first decades of the 20th century, indeed, Karl Schwarzschild, Hermann Weyl, and even Albert Einstein, had misconceptions about the theory, which at that time was brand new, and these pioneers indeed had not yet grasped the full implications. They can be excused for that, but today’s professional scientists know better."

Slereah

I think you seem to be under the impression that physicists would actually disagree with that statement

I'm afraid you are mistaken in this

John Duffield

@Slereah : I am under the impression that 't Hooft is saying "Einstein was wrong and I know better".

Slereah

That is only a problem if this is wrong

John Duffield

And then he gives us the Penrose diagrams!

Slereah

2:39 PM

I'm afraid you'll have to actually argue your points rather than show me things

John Duffield

It starts with understanding why light curves downwards in a gravitational field. IMHO people who think they understand GR don't understand why light curves. I do. I've read the Einstein digital papers. Now, you explain to me why light curves.

Slereah

I foresee me trying to explain geodesics and you answering that it is actually about the inhomogeneity of the speed of light

Am I in the right ballpark

Not that it matters terribly much since even in formalisms where space is flat and the gravitational changes the speed of light (à la Pauli-Fierz) you will still get identical solutions

John Duffield

Yes. See the Shapiro quote above.

@Slereah : it matters a great deal. What's the "coordinate" speed of light at the event horizon?

Slereah

For which coordinates

John Duffield

Those employed by the distant observer. See this:

Propagation of light in non-inertial reference frames

The description of motion in relativity requires more than one concept of speed. Coordinate speed is the coordinate distance measured by the observer divided by the coordinate time of the observer. Proper speed is the local proper distance divided by the local proper time. For example, at the event horizon of a black hole the coordinate speed of light is zero, while the proper speed is c. The coordinate speed of light (both instantaneous and average) is slowed in the presence of gravitational fields. The local instantaneous proper speed of light is always c. In an inertial frame an observer cannot...

Slereah

2:49 PM

Still, what is your objection

Coordinate speed will not matter in another coordinate system

And even if we assume a gravitational field, coordinate changes still matter via the gauge invariance of the field

Secret

@JohnDuffield This will be elaborated:

John Duffield

@Slereah : the schoolboy error about what happens at the event horizon. That says a stopped observer sees a stopped clock ticking normally. He doesn't see anything. He's stopped, light is stopped, the clock is stopped.

Slereah

Do you have a mathematical derivation of this

Secret

There's only one invariant speed K (a signal speed which all observer will measure it as the same value) in a lorentz transformation. Therefore, the faster than K signal you saw there will pass through stations A 1,2,3,B in that order as timed by the observer O, but for O', the signal will pass through it in the reverse order like B,3,2,1,A, thus causality does invert for some travelling observers

John Duffield

@Slereah : yes, here you go: c = 0.

Slereah

2:54 PM

That is not a derivation.

John Duffield

Gravitational time dilation

Gravitational time dilation is a form of time dilation, an actual difference of elapsed time between two events as measured by observers situated at varying distances from a gravitating mass. The higher the gravitational potential (the farther the clock is from the source of gravitation), the faster time passes. Albert Einstein originally predicted this effect in his theory of relativity and it has since been confirmed by tests of general relativity. This has been demonstrated by noting that atomic clocks at differing altitudes (and thus different gravitational potential) will eventually sh...

Slereah

Please come back when you have it

(hint : you're supposed to get scalar quantities from an observer, not just take raw tensor components)

John Duffield

I have it, see gravitational time dilation: $t_{0}=t_{f}{\sqrt {1-{\frac {2GM}{rc^{2}}}}}$

What happens when 2GM = rc²?

ffahim

According to Newton's 3rd law every action has an equal and opposite reaction. So why can't I stand on water surface? If my weight (gravitational Force) is exerting a force on water surface and water surface is too exerting equal and opposite force to me, Why do I drown then?

Slereah

Jesus Christ

Let's stop right there, it's not really worth it

5

John Duffield

2:59 PM

@Slereah : it's worth it because it will stop you wasting your time with wormholes. At the event horizon the optical clock stops. Not because of some mathematical derivation. But because the speed of light is zero. Everything stops. Now take another look at 't Hooft's quantum black hole.

Now, why does light curve?

Here's a clue: einsteinpapers.press.princeton.edu/vol7-trans/156?

ffahim

hello... anybody out there?!

John Duffield

Yep.

Secret

3:24 PM

Tachyonic antitelephone in a nutshell, or the reason why you can exploit the causality reversal in some frames to cause a time travel paradox

@JohnDuffield Note that wrt sender of each signal, the signal is actually travelling forward in their coordinate time, the backward direction is only seen from the receiver's point of view

i.e. arrow pointing to the left is from O', which is travelling forward in coordinate time of O', while the arrow pointing to the right is from O, which is also travelling forward in coordinate time of O

vzn

@BalarkaSen think not completely loony looking into some deeper elements of particles & connections with cellular automata eg along lines/ angles of 't hoofts directions. also, "digital physics." yes, loony from pov of current mainstream physics.

John Duffield

@Secret : no you can't cause a time travel paradox. That's a mathematical fantasy. The train goes through stations 1 then 2 then 3 regardless of what some observer does. It doesn't matter how the observer moves, he won't make that train move backwards.

Abcd

(@Blue Is coriolis force is syllabus?)

John Duffield

@Slereah : come on Sam, I'm waiting. Why does light curve? Please don't say "Einstein was wrong and I know better".

Secret

@JohnDuffield The observer won't make the train move backwards, but to him he will see the train moving backwards due to the causality reversal shown in an earlier diagram

so its a matter of perspective

you can still argue that the train moves forward (wrt itself) but different observers will see the motion of the train differently depending on how fast they move relative to the train

Anonymous

3:46 PM

@Abcd It isn't directly in syllabus, but in 2016 there a huge paragraph type question based on it

Abcd

@Blue Now that scares me...I'll have to study it too...Irodov has problems based on it...

Secret

Now I understand: We are so focused towards idea generation and intermixing, which explains why a lot of our actions are accidentally altrustic

John Duffield

4:09 PM

Does anybody want to talk about the mass deficit?

"As an illustration, consider two objects attracting each other in space through their gravitational field. The attraction force accelerates the objects, and they gain some speed toward each other converting the potential (gravity) energy into kinetic (movement) energy".

diobuc eulb

4:30 PM

@Secret im deleting my account, do you have a discord or other thing i can add you on?

@SirCumference you too

Secret

@diobuceulb I have discord, but how to send you invite?

diobuc eulb

wait

it's different now actually

3b0l7u5e#3105

Sebastiano

Good evening to everybody.

diobuc eulb

@Secret

Secret

diobuc eulb

4:33 PM

let me fix that

try now? @Secret

added you

bye guys!!!

stay blue

John Duffield

All : one guy I've bumped into recently is a chap called David Delphenich. He's been translating a lot of old papers. A commendable service, IMHO. There's some fantastic stuff on his website, real eye-openers.

ffahim

According to Newton's 3rd law every action has an equal and opposite reaction. So why can't I stand on water surface? If my weight (gravitational Force) is exerting a force on water surface and water surface is too exerting equal and opposite force to me, Why do I drown then? Pls help me out with the answer.

Balarka Sen

@vzn I was being facetious. I don't know any of the physical details of that theory, I can believe there's scientific merit to it.

I don't really know any physics for that matter, just to be clear on that

Sebastiano

I hope that any users can you help for this question

2

Q: Orthogonality relationship of electric field and electrical potential of two parallel plates

We known that the potential generated by a charge pointwise $q$ is $V(r) = kq/r $ and the equipotential surfaces (in 3D) are spheres centered in the charge with $r\geq 0$ where $r=d(O,P)$, i.e. the distance between the origin and a generic point $P$. In fact if we are in space, where an orthono...

electrostatics electricity potential

best regards

John Rennie

@ffahim the third law doesn't tell you anything about the size of the forces, just that they are equal and opposite.

John Duffield

4:40 PM

@ffahim : because the "force" of gravity makes you tend to move downwards. Whilst concrete provides a cohesive reaction force that prevents your downward motion, a swimming pool does not. Not until you are almost completely immersed. Then if you breathe in and don't panic, you will float. Then you will not down.

Goendo

Hi!

is it possible to get an answer for my homework problem? If I show my attempt, researches and more...

Thanks in advance, wishing my kindest regards.

John Rennie

@Goendo not on the main site, but if you ask in the Problem Solving chat room someone may be able to help.

Problem Solving Strategies

General chat for high school physics. For MathJax see [here](m...

2

John Duffield

Does anybody want to talk about the principle of equivalence? John Norton talks about it in his 1985 paper what was Einstein’s principle of equivalence?

He said it was a special relativity principle that dealt only with fields that could be transformed away. He talked of an old view and a new view, and said "the equivalence of all frames embodied in this new view goes well beyond the result that Einstein himself claimed in 1916".

ffahim

Let's suppose. I am standing on the floor. So gravity is pulling me downwards. I am not going downwards by penetrating the floor, right? Because the reaction force is causing me to stand on the floor. (as reaction force is opposing the gravitational force I am facing constantly). But don't water molecules follow the same? Even for my force if the water is moved from the surface, Air refills the place and still I am exerting Force right? Then why I will drown now?

@JohnRennie @JohnDuffield

John Duffield

@ffahim : the water is a liquid. The water molecules are not fixed in place. You displace them.

Put the water in a cylinder with a sealed plunger, then stand on the plunger, and you do not displace the water molecules.

ffahim

4:53 PM

Is that because of surface tension? @JohnDuffield

John Duffield

In Kevin Brown ‘s mathspages article on the many principles of equivalence you can read that the equivalence principle has undergone several changes over the years.

Anonymous

@BalarkaSen I forgot what the notation $\mathbb{C}[x]$ means. Could you remind me?

John Duffield

John R Ray's 1976 paper on the Principle of Equivalence is well worth a read.

He said "Hence gravitation and acceleration are not equivalent". I'm with him on that. The principle of equivalence applies only to an infinitesimal region. A region of no extent. So it doesn't apply at all.

OK, I gotta go. Bye.

Goendo

5:16 PM

I'm wondering what the difference between Ncos = mg and N = mgcos is.

However, before that, is there any book that you recommend for classical mechanics?

Anonymous

@Goendo For what level? Classical mechanics can be taught at middle school level as well as at the graduate level.

Anonymous

Also, perhaps you mean Newtonian mechanics

vzn

5:36 PM

@BalarkaSen surprised to hear you say that. maybe am a bit edgy after all your quackery denigration the other day. theres far more to look into than cited on that wikipedia pg if you find it notable or attn grabbing for some reason. ps was thinking after we chatted, "hope he is studying (nonmath!) for his tests some )("... :P

Goendo

5:47 PM

@Blue Indeed, I wanna study physics from zero to university level.

By the way, there should be a book which contains every concepts of physics till advanced.

I've seen something like Physics: principles with applications or anohter books I can't tell right now.

Anonymous

@Goendo There isn't any

Emilio Pisanty

ah ha! found it

Goendo

They were good but in some chapters, like Equilibrium, seems like missed everything about it.

Emilio Pisanty

a fairy unction

Goendo

@Blue Why?

Emilio Pisanty

5:48 PM

(cc @Semiclassical)

Goendo

There should be something...

or for newtonian dynamics

Anonymous

@Goendo Because it would be too huge for humans to handle ;)

Goendo

Oh, too right yeah.

What about going one by one?

Anonymous

For basic Newtonian mechanics there are several good books though

Goendo

i.e newtonian mechanics?

You probs know what Lami's Theorem is.

Most of the books missed to explain what it is.

Anonymous

5:49 PM

280

Q: Book recommendations

Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start. All the question...

resource-recommendations faq

Goendo

What is the reason that most of the books missed to explain Lami's Theorem for equilibrium?

Isn't it important or something?

Anonymous

@Goendo That's nothing important anyway. You can derive it yourself if you know the basics of vectors

Goendo

Hmmm

John Rennie

@EmilioPisanty what is that?

Emilio Pisanty

@JohnRennie a fairy unction

a type of unguent

ointment

one whose pronunciation coincides with the way my brain keeps wanting to pronounce "Airy function"

vzn

5:52 PM

@JohnDuffield coincidentally read that recently after linked in here & was thinking about that line wrt you & others reactions to you/ your writing in here. was telling some others about mtg you recently. "he knows some more of the original physics writings eg Einstein better than phd physicists who work with the modified theories. who might not consider that a significant accomplishment/ devalue it."

John Rennie

Aha :-)

Emilio Pisanty

=P

John Rennie

I have to confess I have never heard of fairy unction, and it appears that nice Mr. Google hasn't heard of it either.

Anonymous

I'm disappointed because I expected that to be some food....jelly/jam

Anonymous

(unless that's some edible oinment :P)

John Rennie

5:59 PM

@Blue it doesn't look very tasty ...

Goendo

Might I be homework police?

I can defend our site against homework flamers

Anonymous

@Goendo Sure, take up a pistol

Goendo

@Blue am ready sir

Do you wanna me to bomb them by Physics Stack Exchange Power?

Anonymous

@JohnRennie Heh, it looked like some mixed fruit jam at the first glance but now that I have stared longer, it doesn't anymore

Goendo

@Blue This book seems good.

Kleppner and Kolenkow, An Introduction to Mechanics

now imma be looking for Lami's theorem

Anonymous

6:07 PM

@Goendo Not bad

John Duffield

@vzn : noted. IMHO there are some important differences between some of the things you read in older sources, and some of the things you read in contemporary sources. But for some strange reason it's difficult to persuade some people that these really are important differences.

Anonymous

Not introductory though

Goendo

@Blue Wow, really.

am still unable to find a book which is like I want.

it shouldnt be too hard

Anonymous

Mechanics for Dummies maybe?

Anonymous

They have a Physics I and Physics II series

Goendo

6:09 PM

@Blue Instead of it, I'd like to study physics with a book

Which contains everything from zero to advanced.

vzn

@JohnDuffield think you are on to some distinctions that might be crucial but maybe need to be defined carefully & think slereah has a point about math rigor. btw despite his top achievements & my own admiration/ support there is generally little taste for 't hooft in this room, but that attitude is maybe not misrepresentative of the larger physicist community either.

Anonymous

@Goendo Good luck finding

Goendo

@Blue You should have something to mention

@Blue So isn't Lami's Theorem important?

John Duffield

@vzn : I rather think Slereah hid behind the need for a mathematical derivation in order to avoid answering a simple question. As for 't Hooft, I always thought he was highly regarded by the larger physicist community.

Anonymous

@Goendo Depends on your definition of important

vzn

6:16 PM

@JohnDuffield if its a simple question maybe theres a simple derivation somewhere. again think that maybe distinct terminology is standing in the way. having trouble even understanding what the debate was about & its already aborted lol ... re 't hooft, he is respected but in a way not unlike einstein: apparently not entirely taken seriously by peers despite his accomplishments. also reminds me of wolfram. there are a few characters like that...

John Duffield

@vzn : the simple question is why does light curve downwards in a gravitational field? It's a physics question, not a maths question. And the answer isn't because spacetime is curved.

vzn

@JohnDuffield ofc its also a math question. if you have the right math model it reduces merely to equations. you might realize you are arguing over different math models of a physical phenomena. ie "what is the correct model of this phenomenon..."

John Duffield

@vzn : the important point here if your answer is only some mathematical derivation, you haven't answered the question.

vzn

@JohnDuffield a lot of physics is about reducing questions (about physics) to math... did you notice how many mathematicians hang out in here? barely even "physicists"?

John Duffield

@vzn : maths is a vital tool for physics. But it isn't what physics is.

vzn

6:21 PM

@JohnDuffield you can win over the math addicts if you speak their language.

John Duffield

@vzn : no I haven't noticed that mathematicians hang out here. And I don't think I can win over the "maths addicts" if I speak their language. It's very hard to persuade people that they're mistaken. #

Balarka Sen

@vzn I would like to read about Wheeler's works, it does sound pretty cool. It's true that I don't know much physics - the only fraction I know is based on my mathematical intuition. Re test, I am! Sadly.

Sorry if you took the leg-pulling seriously from that day. It was maybe a bit too persistent.

vzn

@BalarkaSen wheeler has this idea "it from bit" that is highly connected with digital physics. am something of a fan. think you will find much to like in physics, its very broad. re tests, a necessary evil™ so to speak, maybe you will not have too much trouble with low level rote memorization mainly tested etc.

Balarka Sen

@Blue Ring of polynomials in $x$ with complex coefficients

vzn

@BalarkaSen uh, thx, thinking your latest noticeably polite/ nice words seem somewhat uncharacteristic of your style.

Anonymous

6:24 PM

@BalarkaSen Ah, gotcha. Thanks

Balarka Sen

@vzn I don't know much about digital physics but I have read some popular stuff on trying to connect the physical world with eg, process of a cellular automaton (the one I am most familiar with is the Game of Life)

I liked it as an idea. I don't know how the analogy goes

Formally, at least

vzn

@BalarkaSen have specialized in this area myself. think the analogy probably goes very, very deep. it may be deeper than even all currently known physics. ('t hooft + wolfram would probably agree with that statement.) but physicists dont know ("yet") either.

Balarka Sen

I'm open to hearing a concrete mathematical example of the analogy if you want to explain (Where by that I mean I imagine the analogy as a "cellular automaton to physics" dictionary, so I am asking for a word and it's translation in that dictionary)

vzn

@BalarkaSen ok think a nice entry level idea is "gliders" in life. heard of em?

Balarka Sen

Yep.

The ones which produces the tromino-like things infinitely, yes?

By going back and fourth

vzn

6:37 PM

@BalarkaSen right, theres things called "glider guns" also etc, other interacting/ complex behaviors/ phenomena. now think of a 3d cellular automata instead of a 2d one.

Balarka Sen

Oh right ok I was thinking of the glider gun not the gliders

OK, I follow you

vzn

@BalarkaSen just read recently that the gliders were not immediately discovered in the game and were an answer to an open (math) question posed by Conway. guess what it was? anyway re physics (analogy/ metaphor, TBD more rigorously/ mathematically), the big ("soundbite") idea is...

3d "gliders" ≈ particles

Balarka Sen

That sounds like a fair analogy. Because you can make them interact with each other and what not

vzn

@BalarkaSen the basic idea is quite solid, revolutionary even, and details "merely" remain to be worked out by a 21st century einstein.

Anonymous

@BalarkaSen Is there any direct way to find minimal polynomials other than by estimating using the theorem that characteristic polynomials and minimal polynomials must have same roots?

Balarka Sen

6:44 PM

@vzn Is there any law or explicit formula of interaction that interacting gliders in GoL gives that has an analogous mathematical expression as in particle physics? In particular is there a "formal evidence" there might be a connection between these two separate ideas?

vzn

> Conway originally conjectured that no pattern can grow indefinitely—i.e., that for any initial configuration with a finite number of living cells, the population cannot grow beyond some finite upper limit. In the game's original appearance in "Mathematical Games", Conway offered a $50 prize to the first person who could prove or disprove the conjecture before the end of 1970.

> The prize was won in November of the same year by a team from the Massachusetts Institute of Technology, led by Bill Gosper; the "Gosper glider gun" produces its first glider on the 15th generation, and another glider every 30th generation from then on. wikipedia

Balarka Sen

I am thinking of various dictionaries of seemingly uncorrelated branches of mathematics, which are actually analogies between various mathematical formulas. See, for example, Vojta's dictionary.

That's kind of like an 'evidence' to me

@vzn I vaguely remember that story

vzn

guess technically GLIDERS were discovered early but glider GUNS were (one?) answer to the conjecture

Balarka Sen

Yeah.

vzn

@BalarkaSen that is the bridge "thm" that is roughly conjectured by some but still waiting to be uncovered. but my sketch of that is, believe there are some 3d CA rules that lead "without too much trouble" to solitons

Balarka Sen

6:47 PM

Interesting.

vzn

@BalarkaSen another fun/ (even beautiful!) construction, highly recommend it, is to show Life is Turing-complete. a "construction" which btw may involve gliders/ guns etc!

Balarka Sen

@Blue Minimal polynomial divides the characteristic polynomial, so you can inspect the various factors, eg

Anonymous

@BalarkaSen Yeah, other than that?

Balarka Sen

I don't know a more direct way.

Anonymous

That's too much work

Balarka Sen

6:50 PM

I'd like to see one

Anonymous

Ah, hmm

Anonymous

There should be one

vzn

7 hours ago, by Emilio Pisanty

> The fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright brothers. But they also laughed at Bozo the Clown. ─Carl Sagan

Balarka Sen

@vzn I have heard of this theorem. I have seen a simulation of a Turing machine in GoL before somewhere

Fun fact: Minecraft is Turing-complete

@BernardoMeurer How does that make you feel?

vzn

...and the internet riffraff routinely laughs at/ mocks real geniuses, living/ dead/ emerging