The h Bar

12:12 AM

Will we experience another 'Heroic Age' of Physics like the period of 1890-1940? / reddit

1:18 AM

Hi all. Just wondering if I could ask a few simple questions on here. I already put the question on the physics stackexchange and don't want to duplicate it

skullpetrol

Askaway.

2

loltospoon

Hello

skullpetrol

Hi.

loltospoon

For first order non-degenerate perturbation theory, the result is called the first order correction to the ground state energy. What does the word "correction" imply here? Relative to the ground state energy of the unperturbed system, can we say it is a large value or a small value? For example: If the ground state energy of the unperturbed system is 5eV, should I assume that the first order correction will be on the order of <1eV or could it be between 1eV and 5eV?

Kief

1:53 AM

I've edited my question, with my new questions. It's this - http://physics.stackexchange.com/questions/257340/how-to-measure-the-mass-and-balance-point-of-a-human-forearm

Thanks

vzn

2:18 AM

@Secret quite similar to this topic, read a nice essay on it somewhere recently, trying to remember where... also relates to the "no nonmainstream physics" policy here etc en.wikipedia.org/wiki/Demarcation_problem

ZeroTheHero

@vzn We are experiencing now another heroic age. History hasn't shown us what part of current research is heroic. Probably something that leverages non-locality, like quantum information/quantum computing. We'll know in 15 years who the current luminaries are.

DanielSank

3:11 AM

@EmilioPisanty I can't stop listening.

What have you done to me?

GPhys

3:40 AM

sometimes differentiating between mainstream and nonstream physics is a chore

and one I most often have to exercise when reading this site

DanielSank

@GPhys I never liked that rule.

It's another weirdly subjective rule.

GPhys

at least I occasionally learn something after a lot of effort

I was reading a question earlier w.r.t. en.wikipedia.org/wiki/Variable_speed_of_light

which lead to a slightly more enlightened understanding of dimensional constants in general

ZeroTheHero

@DanielSank when I was a kid grad student I was in charge of the nut mail. In those days random people sent snail mail letters to the Department and - instead of TA duties - I was in charge of reading the nut mail and answer them.

GPhys

something that wiki page was NOT helpful with, unfortunately

ZeroTheHero

decidedly not mainstream...

DanielSank

3:43 AM

@ZeroTheHero Why did you have to answer?

GPhys

^^ this

DanielSank

Someone in the department decided that was worth someone's time?

ZeroTheHero

@DanielSank yeah that was the policy.

it Joe Public (who subsides this university) wants to write us something then we write back doing our best to answer his questions.

it was quite formative.

I mean... in some cases it was seriously nuts.

but in other cases it was actually quite difficult to answer...

GPhys

(that wiki page seems very poor in general in that I don't really feel it proportionally represents the mainstream physics view, relegated to a paragraph in the bottom)

ZeroTheHero

v.g. evidence that the neutron is not a bound state of proton + electron... the charge works out... the mass almost works out... when you're just a junior grad student looking up experiments on deep inelastic scattering and magnetic moments to properly answer is quite a challenge

some of the stuff was way out there.

mostly some guy or gal reading "The first three minutes" by Weinberg and coming up with his/her pet theory.

but maybe 20% of "nonmainstream" questions were actually pretty deep.

so I have grown tolerant about nutbars...

GPhys

3:49 AM

speaking of popular books, I picked up the meaning of relativity by einstein at a professor's urging and am liking it better than I expected

(I guess this isn't really a popular book - it's a compilation of lectures that actually goes fully into the math of relativity)

ZeroTheHero

by Einstein and Infeld?

GPhys

this amazon.com/…

he suggested we pick it up mostly for the philosophy aspect (the logic used to develop the mathematical approach)

ZeroTheHero

@GPhys depending on your level of tolerance you should get your paws on this one:
https://en.wikipedia.org/wiki/Anthropic_principle#The_Anthropic_Cosmological_Principle

GPhys

I have at least a less jaded view of philosophy than I did as an undergraduate

but I'm not grateful my (private) university doesn't make us answer letters (email or otherwise) from crackpots in order to fund ourselves

although one week into the physics lab I'm teaching I've had the privilege of informing students their attempt at turning in a copied lab from a student last semester would not be sufficient to avoid a zero

ZeroTheHero

These days it's all done by email but I actually enjoyed it as it meant I often had to discuss answers at some length with faculty... much better than marking lab manuals.

of course there is also this one: amazon.com/Science-Faith-Society-Phoenix-Books/dp/0226672905 which is truly magnificent.

I remember this letter... from a farmer who grew apples... about the maturity of light...

redshift was not really redshift but rather the photon was getting more mature...

like an apple that ripens from green to red, or a leaf that turns red in Autumn.

interesting moment.

GPhys

4:06 AM

How did you respond to such things?

ZeroTheHero

with great patience.

I remember looking up the actual spectral data and the sequence of astronomical markers..

and of course lurking in the background were all these "tired light" theories...

of which this "maturity of light" can be considered as a fringe example.

I remember looking up all the debate about this "tiring light" business... it was not uncool.

GPhys

I have never heard of such a thing

ZeroTheHero

Tired light

Tired light is a class of hypothetical redshift mechanisms that was proposed as an alternative explanation for the redshift-distance relationship. These models have been proposed as alternatives to the models that require metric expansion of space of which the Big Bang and the Steady State cosmologies are the most famous examples. The concept was first proposed in 1929 by Fritz Zwicky, who suggested that if photons lost energy over time through collisions with other particles in a regular way, the more distant objects would appear redder than more nearby ones. Zwicky himself acknowledged that any...

vzn

aha here it is, delightful/ cool article on crank physics/ brief mention of the demarcation problem

Aug 12 '16 at 8:04, by David Z

This is kind of interesting: "What I learned as a hired consultant to autodidact physicists"

GPhys

hmm

my email is public on my university's website under the listing for graduate students (even nearly at the top, due to my name), but I haven't managed to attract crank emails yet

they do display the email as an image to avoid (trivial) bot collection, at least

ZeroTheHero

4:17 AM

you'll get there.

GPhys

I do get the occasional email from quantitative finance groups here in NYC though....

ZeroTheHero

especially if you start going to conferences... you always have some weirdos who manage to get their hands on mailing lists.

vzn

@ZeroTheHero yes myself think a 2nd quantum revolution is currently underway & probably also something in dark matter/ relativity/ gravity but that it will take at least 1decade to play out much. the operative principle/ modus operandii that keeps going thru my head is rome wasnt built in a day. do you have a physics degree? masters?

ZeroTheHero

better than that!

fully blooded.

vzn

← just luv the coy academics, a rare breed

@GPhys job offers? something else?

GPhys

4:25 AM

@vzn invitations to seek one, at least

(so no)

vzn

@GPhys hah yeah some people dont make that distinction. dont recall did you meet KK in here? hes a working quant with Phd physics degree (cosmology)

ZeroTheHero

@GPhys I actually have several friends who migrated to finance after PhD... from my PhD days Tony the Tiger, from my teaching days Ryan the human computer...

... worked well for them... from quark-gluon plasma to portfolio modelling.

GPhys

When investigating the career paths of those who came before me at the universities I was accepted to I found that, at least in HEP-ex, data science was a popular option

ZeroTheHero

that sounds about right...

vzn

4:43 AM

@GPhys you said you were doing comp experiments earlier? what kind?

GPhys

@vzn nope

but I took a computational physics class last semester as part of required PhD coursework

and that seems likely a source of confusion

vzn

Dec 10 '16 at 3:05, by GPhys

decked out enough that it's actually useful to run my long computations on (!)

@GPhys so what kind of stuff did you simulate?

GPhys

my final project was a galactic merger simulation (entirely newtonian)

where the useful point was mostly just the computational techniques

vzn

@GPhys what kind of code? btw cant recall did we talk about this? plz consider it, @ZeroTheHero & you too :) meta.physics.stackexchange.com/questions/7783/…

ZeroTheHero

when I retire... :)

vzn

4:51 AM

@ZeroTheHero (sigh) dont forget part of science is communication, wink

GPhys

I found a gif on my drive of an early low particle attempt I did i.imgur.com/gRebwaS.gifv

2

shortly after this I started rendering as movies so it's not as easy to share

ZeroTheHero

I leave the AMA to the SE elders.

GPhys

although even this early attempt "correctly" shows the disc galaxies merging to an elliptical galaxy

I don't think the simulation at the time of that gif had included black holes yet

vzn

@ZeroTheHero "SE elders"? huh? unf the high rep users are quite noncommittal these days. :(

@GPhys nice! ... we have a lot of coders in here if you want to talk a few )( details sometime

GPhys

somewhere I have an ugly graph I had python output about the symplectic integrator I wrote

yeah, here it is i.imgur.com/2dtXJ4d.png

well, I wrote all of these differential equation solvers, but

the left is a graph in the error of a determination of the orbit of mars vs the exact solution (which I coded from the well known exact solution (it's just a transcendental equation))

after 2 years or something

ah, it says on the plot, 5 years

this was to verify the convergence of the symplectic algorithm, and then the right plot was just to verify that it's actually preserving the phase space area (so, energy in the case of mechanics)

which is why it was used over, e.g., RK4 for a many particle system (don't want the energy diverging)

our professor said that a high order symplectic integrator was nontrivial code, but it's actually just a matter of figuring out that you just need to grab some constants from relevant literature and then it's not much different from coding any other DE solver

I felt like I cheated the difficulty of the final project even though this topic was suggested, so I spent the rest of the time learning to code it onto a GPU in python

vzn

5:46 AM

@GPhys cool, so, written entirely in python? did you use any libraries? did you write the DE solver yourself? is there a GPU library? CUDA? do you have an idea of your phd topic yet, what area of physics are you researching? GPUs are a big deal in big data/ deep learning these days...

Secret

@ZeroTheHero @vzn The issue of "What is real and what is unreal?" is a more general question than how to distinguish mainstream and non mainstream. While it is true that most pet theories are cranked, a small number of them are actually careful enough to match experiment and such to become new theories some long time later. Although if we restrict our attention to crank theories vs plausible theories (mainstream or not), then yes the reality will impose a strong enough selection criteria to tell

them apart. I am also wondering about questions of even more general existence. Perhaps there really exists unrepriducible entities and phenomena, thus pretty much will make them immune to query via the scientific method. But do the universe has a universal standard on what is real. I am not even sure if the answer to this question is well defined

GPhys

@vzn Yes, I wrote the DE solver(s) myself from just Python and numpy

and then made the efforts to transfer that numpy implementation into one making use of a python GPU library

DanielSank

@GPhys cool!

Secret

6:06 AM

1

Q: If photons have a finite mass, will black holes emit a factor 3/2 more electromagnetic Hawking radiation?

An old but wrong argument that photons must be exactly massless is to observe that black bodies radiate according to the Stefan–Boltzmann law and then argue that if photons were massive they would have 3 polarizations and therefore would have to radiate 3/2 times the power predicted by the Stefan...

hawking-radiation

Hmm... I rarely think about physics involving nonzero photon mass

vzn

@Secret nonmainstream physics is generally considered "not real"! by physicists who largely reject the concept of realism! :P think you have some excellent questions that are considered in metaphysical literature which is large...

GPhys

I used to rarely think about nonzero photon mass physics until our E&M professor pointed out he was a coauthor on a theoretical paper cited by the particle data group on photon mass limits and that he wanted us to understand a part of it

Q_Q

(last week, too)

skullpetrol

6:24 AM

Feynman once said that the philosophers who spent too much time pondering about whether the steak in front of them was "real" or not have fallen by the waist side through hunger.

user228700

7:38 AM

Hi, everyone :-)

skullpetrol

Hello.