The h Bar

1:32 AM

0

Q: Is non mainstream physics appropriate for this site?

Under construction Note: This is not a new policy, just a meta post about the old one. It will be linked to in the new close reasons. Is non mainstream physics allowed here? What defines non mainstream physics? What should I do if I see a question or answer containing non mainstream ph...

David Zaslavsky

2:04 AM

@ArnavTripathy yeah, sometimes. But not always. Chat isn't only for physics discussion.

ManishEarth

2:25 AM

@ArnavTripathy fwiw that whole 4 hour discussion was a scheduled chat session for working out the close reasons

We also have religious debates on programming languages

Oh oh and trolley cars

usually it's physics related though (or Physics.SE related)

user54412

3:41 AM

@tpg2114 I'm here

tpg2114

Hey

So I don't really know what to think about some of those questions tagged that way and what is "engineering" vs "physics"

What about statics for example?

Is that at all physics really? Or just pure engineering?

user54412

hmmm

David Zaslavsky

Statics problems are usually done in intro mechanics classes

user54412

most of the stuff in statics I think could be construed as physics

user54412

except for things like this

user54412

3:44 AM

0

Q: The stress in copper and steel parallel compound members

Came across this question and just needed abit of help undertanding how i should go about this question I have also attempted to solve it to the best of my ability but im stuck. A concrete column of square cross-section of 250mm x 250mm & 1.5m long is required to support an axial compressive lo...

homework engineering statics stress-strain

tpg2114

But our statics classes are in the College of Engineering for example

What about:

1

Q: Trying to avoid a physical structure tipping over

I am trying to build an aluminum stand (tree). The "trunk" is 72" (1.8288$\,$m) tall. There are four perpendicular (outstretching) "branches" along the top half of the trunk, each 36" (0.9144$\,$m) in length. These arms will be at different angles to the trunk, but all forward in one direction wi...

newtonian-mechanics engineering statics stability

user54412

I'd be okay with closing that as engineering

user54412

I'd be more okay if we had a dedicated mech-E site

David Zaslavsky

A whole tag isn't necessarily going to be on or off topic

tpg2114

@DavidZaslavsky I agree, but it's missing a tag-wiki

So if we can define somehow what "engineering-statics" is vs "physics-statics" and put that in the wiki

It would help

David Zaslavsky

3:46 AM

Sure

tpg2114

Along with defining how engineering should be used (which is what I originally suggested Chris talk about but got quickly sidetracked with statics)

David Zaslavsky

I don't have any particularly good ideas beyond stating the obvious: that statics is for situations in which nothing is moving

user54412

aha - one day there may be Mechanical Engineering for us to point people toward

David Zaslavsky

Yeah, that'll be good

but that's a long way off

user54412

@DavidZaslavsky you should make that the entirety of the wiki: "statics is for situations in which nothing is moving" :P

David Zaslavsky

3:48 AM

lol :-P

well, if nobody else comes up with anything soon

We should also think about whether we should even have engineering as a tag, given that engineering questions are supposed to be off topic

tpg2114

@DavidZaslavsky That's what I originally pinged Chris for

user54412

@DavidZaslavsky yeah that's the issue

tpg2114

To have that conversation and come up with a proposal to put on Meta

user54412

I think with an appropriate wiki (and importantly a good mouse-over summary) it can be good to have

tpg2114

Re statics: The study of stationary systems

I don't think it needs to be any more verbose than that honestly...

David Zaslavsky

3:51 AM

@tpg2114 that works

tpg2114

What kinds of on-topic questions would still have engineering?

user54412

I mean, electric-circuits and sun exist, but that doesn't mean we condone "design my breadboard" or "how do I build a solar panel" questions

tpg2114

But we don't have physics

user54412

@tpg2114 I think the critical distinction is inspired by engineering

David Zaslavsky

People do often take the existence of a tag as an indicator that the subject of the tag is largely on topic. They shouldn't, but they do.

tpg2114

3:52 AM

So if we say "engineering for engineering's sake" is OT, I don't know that engineering is all that useful

David Zaslavsky

I'm really just not seeing why that tag would be useful.

user54412

questions where a physical principle was brought to the forefront when investigating an engineering issue

user54412

well, I don't have any particular attachment to it

tpg2114

Nor do I, but before proposing to kill it off I'd like to find out if there's some reason to keep it

Your example of on-topic engineering, "Why do airplanes fly?"

Should that have engineering?

Does it add anything to have that tag?

user54412

wasn't my example - Manishearth picked that one out

tpg2114

3:55 AM

Heh, okay. Well "the example" then :)

user54412

it does seem strange to tag it as such - we have aircraft and airplanes

user54412

(which are fortunately synonyms)

tpg2114

Not entirely synonyms

user54412

I mean, we implemented synonymization

tpg2114

aircraft could include blimps, balloons technically

I guess it is a synonym here...

user54412

3:57 AM

true, which is why the directionality is airplanes is replaced by the more general aircraft

tpg2114

Oh well

user54412

well, if you think of a good blimp question...

tpg2114

I'll come up with one :)

user54412

"How much hydrogen do I need to lift my zeppelin?"

user54412

It may be an "actual problem you have faced" for someone I suppose

tpg2114

3:58 AM

The navy actually started designing a new fleet of blimps

They're slightly heavier-than-air if I recall

jacksonville.com/news/metro/2013-04-01/story/…

Heck, apparently yesterday they were testing them in Florida to track drug runners in the Gulf

user54412

heavier than air? umm.... I may not be a pilot, but...

tpg2114

American Blimp MZ-3

{| |} The MZ-3A is a blimp owned by the United States Navy since 2006. It is a modified American Blimp Corporation A-170 series commercial blimp and given the USN type/model/series (T/M/S) designation MZ-3A and Bureau Number (BuNo) 167811. After delivery to the Navy, the airship began operations as an advanced flying laboratory used to evaluate affordable sensor payloads, the development of new lighter-than-air (LTA) technologies and general flight support for other related research and development/science and technology (R&D/S&T) projects. In May 2006, Air Test and Evaluation Squadr...

It just means they have to use some engine power to help it stay in the air

As opposed to traditional blimps that just floated freely

Every airplane is "heavier-than-air"

Anyway, sidetracked again

I'm looking through the engineering questions and a) I don't see many that should be left open and b) I don't see any that should be left open that couldn't do without the tag

Which also opens the question about electrical-engineering as well

user54412

my take on the 5 most recent [tag:engineering] questions:
1) [No idea](http://physics.stackexchange.com/questions/70245)
2) [Good - material properties](http://physics.stackexchange.com/q/69885)
3) [okay - units inspired by engineering](http://physics.stackexchange.com/q/69885)
4) [bad - homeworky and too complicated an engineering issue](http://physics.stackexchange.com/q/69199)
5) [good - physics underlying a device](http://physics.stackexchange.com/q/69175)

user54412

^ No idea why those links didn't format

tpg2114

The heat sink one and the structure tipping over I'm not sure about really

As posed, it's more like "Help me design this object" which is engineering

As opposed to "How do I analyze a physical structure set up like..." or "What material properties are important for a heat sink"

Respectively

user54412

4:09 AM

6) [the engineering part is the bad part; takes focus away from physical limits](http://physics.stackexchange.com/q/68656)
7) [that this was inspired by engineering is irrelevant](http://physics.stackexchange.com/q/67843)
8) [just plain engineering; not physics](http://physics.stackexchange.com/q/67518)
9) [not engineering (or even EE); just circuits](http://physics.stackexchange.com/q/67381)
10) [would be physics with a diagram perhaps; but with words undefined terms sounds like engineering](http://physics.stackexchange.com/q/67184)

user54412

@tpg2114 yeah, I can see that

user54412

that might be a good point for the faq: "help me design" vs. analysis of something fundamental

tpg2114

Okay, so I think I'm with @DavidZaslavsky on this one... I don't see a need for the tag really. Questions that should still be open don't really need the tag and the ones that seem to need it are off-topic

user54412

that seems reasonable

user54412

I wonder what applied-physics has to offer

user54412

4:13 AM

I always felt applied physics was materials and optics and nanostuff

user54412

but this meta post: meta.physics.stackexchange.com/questions/4304/… indicates some people use it synonymously with engineering

tpg2114

From an outsider and in a naive way, I took applied physics to mean "Physics that has an influence in every day life"

user54412

and a brief look at applied-physics tells me it is used synonymously with engineering

tpg2114

Like... if the Higgs exists, it doesn't change how I get to work in the morning

user54412

hmm

tpg2114

4:16 AM

FWIW, the association of applied physics with engineering seems to go back to early days

4

Q: Are engineering questions OK?

What would be the real-world implications of the Kessler Syndrome? is essentially an engineering (applied physics) question. If we ignore the specifics of that question, should we accept applied physics questions here? To suggest another example in the same category: "Can you use any semiconduc...

discussion scope

user54412

I guess I just knew enough applied physics majors as an undergrad, and basically all they did was cool things in labs involving optics benches and poisons and really cold things

tpg2114

I'm an engineer, so I didn't get to make that distinction. Although I could see it as "physics that can measure tangible things"

As opposed to the thought-experiment kind of physics

user54412

hmmm - I always though measuring things was experimental physics

tpg2114

That could be too

I don't really know what the distinctions are

user54412

and applied physics was engineering but with not-so-tangible things (or at least, things that required an SEM to see)

user54412

4:19 AM

probably depends on the school

tpg2114

0

Q: What is the fate of the engineering tag?

Given the discussion related to whether Engineering questions are on topic, we also need to consider whether the engineering tag has any reason to exist. We discussed it in the chat room using the most recent questions, the transcript of which can be found at: http://chat.stackexchange.com/rooms...

discussion tags

user54412

I don't know why the other engineering disciplines have been so slow to get sites of their own

tpg2114

My Solid/Fluid Mechanics proposal was deleted :(

Inactive for 30 days

user54412

:(

tpg2114

For the FAQ: "Questions about the physical reasons and analysis that lead to design decisions are on topic; questions seeking help designing or building something is off topic."

"physical reasoning" is probably a better phrase

user54412

4:26 AM

sounds good - feel free to add it

tpg2114

Done

Any other tags that need to be sorted out based on the close reasons?

user54412

I think homework and mathematical-physics already have good summaries

user54412

perhaps we should create a non-mainstream tag :P

tpg2114

crackpot-theory

serious-level-physics

user54412

new-approach-to-physics

tpg2114

4:35 AM

The only engineer tags we have are engineering nuclear-engineering electrical-engineering

user54412

nuclear-engineering is a mixed bag - it certainly has its fair share of closeable questions

tpg2114

Yeah, and it has some questions that don't really need it

0

Q: Could one "build" elements?

I was wondering this: would it be possible to "construct" elements by arranging their constituent particles in high-energy environments? So apart from just fusion, could you sub-atomically manufacture elements?

particle-physics atoms popular-science nuclear-engineering fusion

That doesn't seem to be what I would define nuclear-engineering

user54412

on the other hand, it keeps nuclear-physics free of junk and focused on the finer points of, well, nuclear physics

tpg2114

To me, nuke-engineering is the design/operation/physics behind power systems based on radiation

Although I guess it also includes medical uses of radiation

user54412

agreed

David Zaslavsky

4:39 AM

I guess that one could become nuclear-technology or something

user54412

while we're at it, what on earth is going on with nuclear-isomers?

tpg2114

How did that even get created

user54412

is that question even about nuclear isomers?

David Zaslavsky

People create all sorts of random tags

tpg2114

What's the rep barrier? I thought it was higher than 1700

David Zaslavsky

4:40 AM

Nah, tag creation is possible without much reputation

user54412

300

David Zaslavsky

Anyway, the question does actually concern nuclear isomers, and while it probably didn't need that tag, I don't think it hurts

tpg2114

Submitted a tag-wiki for nuclear-engineering

But I don't have enough rep so it's pending...

user54412

it's strange to hear the word "manufacture" used in the context of short-lived metastable states

tpg2114

Well, an excerpt anyway

Is there a way to search for tags that have no tag-wiki?

user54412

4:44 AM

the review for that is quite hidden - I don't know if I would have ever known there was a pending edit without being told

user54412

not that I know of - I just browse all tags and visually pick out the ones without exerpts

David Zaslavsky

@tpg2114 Maybe using data.SE, but I don't think there's any way in the site search

tpg2114

I think we should also kill off image-processing, bernoulli-equation and log-graphs

Although mixed feelings about bernoulli-equation. I mean, we have tags for Navier-Stokes and Fokker-Planck and some other famous equations

But that seems a bit too specific to me

David Zaslavsky

@tpg2114 I think that one could stay

tpg2114

That works for me

David Zaslavsky

4:48 AM

I'm ambivalent about it, but it's a thing that people can ask questions about, so I don't think it's really inappropriate as a tag.

tpg2114

Yeah, agreed

user54412

hmm - when exactly did quantum-computation and quantum-computing get mapped to quantum-computer?

Physics Meta

2

Q: What is the fate of the engineering tag?

Given the discussion related to whether Engineering questions are on topic, we also need to consider whether the engineering tag has any reason to exist. We discussed it in the chat room using the most recent questions, the transcript of which can be found at: http://chat.stackexchange.com/rooms...

discussion tags

user54412

especially given that the synonym was proposed the other way:

user54412

user54412

4:54 AM

@tpg2114 log-graphs should definitely go (and I'm saying this as an astronomer - I've never plotted something that wasn't a logarithm)

tpg2114

Yeah, that's a sort of silly, oddly specific tag for our site. It might make sense on Cross Validated or something

user54412

to be fair, I don't know what else to tag that question as

tpg2114

data-analysis

Would be appropriate

user54412

good call

tpg2114

I didn't know that tag existed... huh

Learn something new every day

I would have proposed creating it

user54412

4:58 AM

well, there are no more log-graphs questions anymore ;)

tpg2114

Also true :)

I'm putting in tag-wiki's

There should be several more to review

David Zaslavsky

OK, just took care of those

...busy day on chat today :-P I haven't done any work the whole day

tpg2114

I spent all day setting up a bunch of cases on a supercomputer

And then they emailed out an unannounced outage for 2 weeks to deal with some system upgrades

So I lost the day of work

user54412

:: continues to touch up unnecessarily long paper ::

user54412

observational astronomy - wayyy too much data analysis per unit publication

tpg2114

5:03 AM

I have the opposite problem... I'm trying to make up analysis to fill out a paper

Unfortunately, high explosives are well studied but not well understood

So there's only like 2 numbers to compare to and little additional analysis

Hrm... how do we handle tags like beam where it could mean "Physical structure whose length greatly exceeds it's height and thickness" and "Light beam"

user54412

LOL - it really has been used for both

tpg2114

I know...

user54412

Tag wiki suggestion: "A near-continuous stream of metal bars moving at high velocity"

David Zaslavsky

@tpg2114 come up with two more specific tags to refer to the two cases, and edit the existing questions to assign the appropriate more specific tag

lol

tpg2114

structural-beam and light-beam? Is there another possible meaning in particle physics or something I don't know about?

David Zaslavsky

5:07 AM

Beam theory is actually a thing that could use a tag

@tpg2114 The beam of particles in an accelerator is also called a beam, but that doesn't necessarily need a tag

tpg2114

I guess light isn't correct

Electromagnetic energy?

There's no requirement it has to be in the visible spectrum to be a beam

David Zaslavsky

Honestly, light-beam would just be replaced with electromagnetic-radiation or visible-light as appropriate

Euler–Bernoulli beam theory

Euler–Bernoulli beam theory (also known as engineer's beam theory or classical beam theory) is a simplification of the linear theory of elasticity which provides a means of calculating the load-carrying and deflection characteristics of beams. It covers the case for small deflections of a beam that is subjected to lateral loads only. It is thus a special case of Timoshenko beam theory that accounts for shear deformation and is applicable for thick beams. It was first enunciated circa 1750, but was not applied on a large scale until the development of the Eiffel Tower and the Ferris wheel...

tpg2114

So replace beam with structural-beam? Cause there's other beam theories

David Zaslavsky

Sure, sounds good

tpg2114

Euler-Bernoulli is one, Timoshenko is another

David Zaslavsky

5:09 AM

Oh right, that's the one I was thinking of

According to the wiki excerpt, E-B is a special case of Timoshenko

tpg2114

Timoshenko includes shear

E-B ignores shear

David Zaslavsky

and I remember this now, because I wrote a blog post using it

a long time ago

tpg2114

I just took a computational structural mechanics class in the spring

David Zaslavsky

@tpg2114 Anyway, structural-beam seems like a fine tag. I'd say go through the beam tag and for anything where it refers to light or EM radiation, remove beam and replace it with either electromagnetic-radiation or visible-light as appropriate. Then I can rename beam to structural-beam using the mod interface.

tpg2114

Okay, I was creating structural-beam anyway, there's only 14 questions total

But I'll stop changing beam over and let you do it, give me a few mins

David Zaslavsky

5:13 AM

Sure, or if you wanted to manually edit all beam into structural-beam, that does the same thing

Figured I'd save you some effort though

tpg2114

Do we bother to retag closed questions?

David Zaslavsky

hm... I would

just to keep things proper

4

Q: Mirrors and light beam divergence technology limits

There are many applications for orbital space mirrors in astronomy (better telescopes) and space propulsion (solar power for deep space probes), but this is limited by the minimum beam divergence achievable with current technology So, i'm trying to understand what physical and technological limi...

astronomy propulsion experimental-technology solar-system-exploration beam

I would have thought electromagnetic-radiation for that one

Nothing seems specific to visible light as far as I can tell

Actually this too:

0

Q: Width of Gaussian Beam and Refractive Index

I know that in free space, the width of a Gaussian beam can be written as $W=W_0\sqrt{1+(\frac{z}{z_0})^{2}}$. However, I was wondering if it was possible to express this width as a function of refractive index instead (since I don't believe a Gaussian beam originating in say, glass, will diverge...

optics waves visible-light refraction beam

@tpg2114 oh wait, I just remembered, the reason not to edit beam -> structural-beam manually is so we don't push all those questions to the top of the site at once

tpg2114

I stopped, I only did it on 2

And you can reject those edits

Cause I'm not at 2k rep yet

David Zaslavsky

Nah, I approved, because why not :-P

It doesn't really matter for only 14 questions

less than that even

tpg2114

-1

Q: muon neutrino momentum distribution

muon neutrino momentum distribution I have read the public data of T2K ,KEK to find this subject, I'm curiously that it's coincides with my prediction perfectly: The neutrino get its momemtum by its effect-partner, which is obvious in the reactional formula, especialy that by me. You can find t...

particle-physics neutrino beam

What about that? It's a really bad question, but it looks like particle-beam right?

David Zaslavsky

5:19 AM

Yeah

tpg2114

So create a new tag with that one?

David Zaslavsky

Maybe, or maybe just drop beam and don't put a replacement

Actually, it could use experimental-physics

because it seems to be asking for details about an experiment

tpg2114

Done

That should be all of them, let me double check

David Zaslavsky

beam-propagation-method is a tag? I didn't know that was a thing ;-)

tpg2114

It was a tag, I didn't know it was either

But it popped up so I figured it was used at least once before, might as well give it a second one :)

David Zaslavsky

5:21 AM

huh, weird, I didn't see any other questions using it in the list

Maybe there's a deleted question or something

anyway

it does fit the question

tpg2114

physics.stackexchange.com/questions/tagged/…

There's 2

Now, one other

0

Q: equilibrium intensity Helmoltz equation

Helmoltz equation describes the evolution of the bulk electromagnetic field, even when doing scalar optics as an approximation. Beam Propagation Method is a common approximation that assumes certain simplifications, in particular only forward propagation is taken in consideration. The benefit of...

boundary-condition eigenmode-expansion beam-propagation-method

David Zaslavsky

Oh, I must have looked at the list before approving the edit

I wasn't paying attention... I'm tired ;-)

tpg2114

Let me know when you rename, I'll edit the new structural-beam wiki

David Zaslavsky

OK, done

user54412

such a mess of tags in general

David Zaslavsky

5:24 AM

I guess you didn't actually need to wait for me

tpg2114

Yeah, it's all good...

user54412

@tpg2114 aiming to be the first person on the site to get research assistant?

David Zaslavsky

@ChrisWhite indeed. But I think SE handles it about as well as any site I've seen

tpg2114

@ChrisWhite No, unable to sleep and unwilling to do any of my actual work :)

tpg2114

5:36 AM

I don't want to define things like computer...

user54412

"the thing you are currently using"

tpg2114

Yeah...

Too bad my edits still need to be approved

I can't Easter Egg things in

user54412

David and I are both tired - you probably can

user54412

especially given the broken parsing of the edit-review diff engine - if you mix tex and markdown thoroughly enough, the diff it shows probably will omit some parts of the edit

tpg2114

I want to put conventions as "A gathering of similar-minded people"

user54412

5:40 AM

LOL

user54412

"A chance to network with people in your field"

tpg2114

current: "Presently happening or still relevant. To be contrasted with historical or antiquated"

Okay, I think I'm done before I start putting in jokes for everything

I'm at like +50 rep for edits in the past 30 minutes. Sadly, one of my higher earning days

user54412

@tpg2114 that's quite a lot

tpg2114

Too bad there's no rep for flagging

user54412

@tpg2114 congrats - you no longer need approval to edit Q's and A's

user54412

5:51 AM

:)

tpg2114

I know... I just saw that

Sad, I can't make people approve my work :(

user54412

I may have upvoted an answer of yours so I would no longer have to peer review your work :P

user54412

(it was also a good answer I hadn't read before)

tpg2114

I figured that's what happened... :)

tpg2114

6:18 AM

If you want to keep upvoting...

0

A: Conservation Vs Non-conservation Forms of conservation Equations

What does it mean? The reason they are conservative or non-conservative has to do with the splitting of the derivatives. Consider the conservative derivative: $$ \frac{\partial \rho u}{\partial x} $$ When we discretize this, using a simple numerical derivative just to highlight the point, we g...

:)

That one was actually a question on my qualifying exams... shudder

user54412

@tpg2114 have your upvote :P

user54412

not sure what prompted that person to post on mathoverflow originally

tpg2114

stackoverflow*

user54412

derp

user54412

I can read

user54412

6:22 AM

still an unfortunate choice

tpg2114

That's where I get confused sometimes about what is homework or not... Proving conservation/non-conservation was a homework problem for us

And then it reappeared as a quals question

user54412

were your quals oral or written?

tpg2114

Oral

3 subject areas, each with 2 professors. 1 hour for each area

Each area had 2 classes primarily, but anything they considered background or anything you were stupid enough to bring up was fair game

user54412

hmm, mine was oral - 4 subjects, 1 prof each, all together for 2-2.5 hours total

user54412

oh - we didn't even have to bring stuff up

user54412

6:25 AM

our profs told us they intended to explore the boundary of our knowledge, not the interior

tpg2114

Ours were separate... They would get together afterwards and vote. 5 of 6 or 6 of 6 passed

We didn't have to bring stuff up either... but they might say "Tell me how an airplane flies"

And if somebody said "well, the batteries turn on the engines when the pilot turns the key," they might start grilling you for the full hour about how batteries work

Or why it's a key and not a button

user54412

I didn't get asked a single question about topics I was comfortable with (GR, dynamics, planets, stellar structure) - instead it was all stuff I was completely clueless on (galaxy evolution, how radio telescopes work)

tpg2114

For us, it depends on the exam... for shear flows, it was a guarantee we'd get a question about Einstein summation notation

user54412

I like the sound of that

tpg2114

But then for gas dynamics, those guys just liked to give people a hard time. They made me spend 10 minutes deriving an equation from undergrad and then told me I didn't actually need it and wasted time

And then I derived something else and he said "That's wrong." but it wasn't, he just wanted me to defend it a different way

It's academic hazing.

user54412

6:31 AM

I have to remember what I got wrong in quals - apparently various faculty in my department have a habit of re-asking the questions we bombed on during our thesis defense

tpg2114

Even if it has nothing to do with your thesis?

user54412

indeed ;)

tpg2114

Ouch

user54412

hmmm... that reminds me - I need to settle on a thesis topic/adviser pretty soon

tpg2114

I think our thesis defenses are already so rough when they rip apart what we did, they don't need to bring up our past failures

I have to do my proposal by Sept

user54412

6:35 AM

basically, i'm deciding between hydrodynamics + stellar structure, hydrodynamics + star formation, hydrodynamics + supernovae, hydrodynamics + neutron stars, or hydrodynamics + plasmas

user54412

lots of simulations in my future...

tpg2114

We have people in our lab that work on plasma and MHD

More from a fundamental level... turbulence and mixing mostly

Lots of boxes with imposed fields

I'd go for star formation

That sounds cooler

user54412

something sounds cooler than ~~supernovae~~ EXPLOSIONS!?

tpg2114

I get enough of explosions in my work :)

user54412

well, my latest recompiled tex crashed my pdf viewer - time to head to bed

tpg2114

6:46 AM

Goodnight, thanks for approving lots of edits!

ManishEarth

boo!

@ChrisWhite use writelatex.org

Oh, pdf viewer. O_0

Whoa, chat has been busy.

@tpg2114 Nope. However, it's a type of physics question that sounds like an engineering one. Which is why I gave it as an example

David Zaslavsky

8:02 AM

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Q: Life without quantum mechanics (Technology which couldn't exist, if humankind didn't know QM)

The GPS is a very handy example in explaining a broad audience, how general relativity influences our lives: it just so nicely bridges the abstract theory with daily life technologies! I'd like to know an analogous example, but for the quantum theory (I guess that I should say quantum mechanics, ...

quantum-mechanics soft-question engineering applied-physics technology

List question?

ManishEarth

Broad, but not that bad. I'd refer it if it restricted itself to past tech

Nix

12:08 PM

the question- life without QM is speculative. Does anyone agree?

Dilaton

12:28 PM

@Nix nope :-). Asking for a corresponding example to demonstrate the usefulness in everyday-live of QM as we have it with GPS for GR is a reasonable question. Calling the question speculative because of this specific formulation is just (language-) nitpicking, it could easily be reformulated without changing the essence of the question.

I also disagree with @DavidZaslavsky that the question should be closed as a list question, just because it ask for an example to demonstrate something. As I understand it the question is meant to find one (or a small number of) good example, there may not exist an indefinite number of them when thinking rationally about it.

twistor59

Is anyone keeping a record of the best PSE question titles? This qualifies surely: physics.stackexchange.com/questions/70573/…

Dilaton

Hi @twistor59, did you see my last comment directed at you ;-)

There are some good questions in the reopen queue now that should be reopend and they already have 4 of the 5 votes needed ...

twistor59

12:57 PM

@Dilaton I'll have a look. Haven't checked that queue for a while...

Dilaton

@twistor59 thanks cool :-). I think in particular this should not stay closed (but the others with 4 reopen votes neither...), as the experts knowledgable in the topics such as Lumo and pho etc finally agree that the question is a good one and could get interesting answers. And I vaguely remember that Lumo sometimes writes about Moonshine, Monstergoups, and their importance in ST on TRF etc ... Have you been away?

I did not see you for some time and was already worried ;-). The slapping an insect into unconciousness question is funny indeed :-D

twistor59

There were only two in the queue, both of which I thought were perfectly reasonable.

@Dilaton No, not been away, just very busy with real work that pays my bills!

Dilaton

1:21 PM

@twistor59 there is also this question ...

... and that one. No idea how they have disappeared out of the queue

Good to see that you are still around :-). I'll be a be a bit busy too, since I want to prepare a talk to show some colleagues that applying renormalization to turbulence theory is cool...

ManishEarth

1:39 PM

@Dilaton In that case ... reformulate it. Remember, the tone of the question sets the type of answer it will get

imo it's not speculative, but it is a list question. But it's not that bad

Dilaton

2:06 PM

@ManishEarth ok I'll try one. The title of the questions seems not to represent very good what the question really asks. And I am not sure if the big-list tag is really needed as I expect the resulting list (if any) of examples to not that big ...?

ManishEarth

Meh, I don't like the big-list much in the first place

user54412

well the life without QM OP is getting what he deserves - ask a question that doesn't make sense (what if everything else stayed the same but this one big thing changed?), get answers that don't say anything

user54412

he now has a list of a dozen technologies that were developed without quantum theory

user54412

plus another half dozen techs that don't affect anyone on the planet at the moment

user54412

physicists - stealing credit from engineers for the past century

Dilaton

2:19 PM

Gosh, I had some problems with the length of the title, but now it is done :-)

Gugg

2:33 PM

Anybody know how the rev counter at the Ashes works? They seem to be able to deduce the revs of the cricket ball almost instantly. How do they do that?

user54412

::asks self: is this about crickets revving up? perhaps they should be slapped into unconsciousness?::

Gugg

lol

user54412

@Gugg but seriously, are you talking about how fast the ball is spinning?

Gugg

Yup. I remember that they can also do that at the golf driving range, but where's the radar on the cricket pitch? Shouldn't it be close?

user54412

actually that's a good point - baseball has a similar issue

Gugg

2:45 PM

I wanted to send a picture, but... they are having tea now.

user54412

I remember hearing that in fact even the supposed speed of baseball pitches is more or less made up - they can't get accurate radar readings for such a small object at such a large distance

Gugg

OK, but that's speed. This is rotational velocity. Must be more difficult.

user54412

indeed

user1504

@dmckee: I don't think that Applications of QM question is a duplicate.

One question is asking for physical phenomena where the quantum nature of reality is readily apparent.

The one you just closed is asking for examples of technologies we couldn't have developed without knowing the rules of quantum physics.

user54412

@Qmechanic I just realized quantum-computation and quantum-computing now point to quantum-computer, but isn't that the opposite direction from your own proposal on meta?

ManishEarth

2:55 PM

@ChrisWhite Yeah, should be the other way around imo

Fortunately, synonyms are reversible. (merger aren't, not really)

Qmechanic

@ChrisWhite : Yes, you recalled correctly. Originally I proposed and later implemented the other way around. However, approximately a week ago, I swapped the synonyms quantum computation -> quantum computer, because people misused the quantum computation tag for apparently any calculation in QM. My thinking is that people will hesitate a bit more to apply the quantum computer tag.

ManishEarth

@Qmechanic did you reapply the merge?

(to rename the base tag)

user1504

@dmckee At any rate, not a duplicate of the question you closed it as a duplicate of.

ManishEarth

Because tags which are synonyms of another but still exist as a tag are very strange

Qmechanic

@ManishEarth : Not for now. I want to see how it works.

ManishEarth

2:59 PM

kk

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