The h Bar

7:02 AM

themonkeycage.org/2009/01/21/hotness

I wonder where's Physics..!!! O_O

Q: not so good questions with well researched answers

8:30 AM

@tpg2114 calling @tpg2114

Physics Meta

9:15 AM

0

A question if I may. What is the policy here about deletion of not so good questions that may have good, well researched answers attached? Are they deleted eventually? Well researched answers often take considerable amount of time to research/write and would certainly be a contribution to the ...

discussion questions answers

Mussri

Hi. I need some help with several 'SF' related questions. That's how I'll consider the answers but you'll just answer normally, in the 'mainstream' way. Anyone interested?

10:53 AM

@CrazyBuddy Science=Physics

12:17 PM

@Mostafa What??? What about Biology, Chem, etc..? Not science?? O_O

They've been addressed separately...

@CrazyBuddy In fact even social sciences are science too, but that's the way the word is often used.

Take a look at the third paragraph of:

Science

Science (from Latin scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe."... modern science is a discovery as well as an invention. It was a discovery that nature generally acts regularly enough to be described by laws and even by mathematics; and required invention to devise the techniques, abstractions, apparatus, and organization for exhibiting the regularities and securing their law-like descriptions." —p.vii, J. L. Heilbron,(2003, editor-in-chief). The Oxford Compan...

@Mostafa Yeah... what's so special about that? It says...

> the word "science" became increasingly associated with the scientific method itself, as a disciplined way to study the natural world, including physics, chemistry, geology and biology.

They're subsets...

12:32 PM

@UV-D What's up?

@Mostafa Anyways, I didn't start it as a discussion... Just sharing the info. ;-)

Maybe physics is more science, because it's more mathematical and so more precise and reliable.

Reminds me of an XKCD... :)

On the other hand, physicists like to say physics is to math as sex is to masturbation.

That may be considered a joke, but I really think it's right. Especially the parts after biologists.

@Mostafa It's true really :)

12:40 PM

I always try to read the whole mathematics involved in a theory/topic in physics and then start reading the physics itself.

It's exactly against the approach of Griffith's books.

Hah..!!! :)

@CrazyBuddy It seems you are an engineering student who loves (to study) physics (like me). Am I right?

@Mostafa Yep... always :D

So why didn't you studied physics (as your major)?

@Mostafa: Sorry... umm... I'll brb within 15 mins (having lunch right now) ;-)

1:07 PM

@Mostafa First, I was interested in aeronautics. So, I joined my college... (the same day, when I snooped into here)

Then, engineering became boring (especially our scheme) :/

But, I can't leave engineering behind (I had only one choice left)

Continuing... (till now) -_-

Q: Question invloving two vectors

3:23 PM

How has this one not been closed yet:

-7

Find the angle between $\vec A+\vec B$ and $\vec A - \vec B$ if $\vec A=2\hat{\imath}+3\hat{\jmath}$ and $\vec B=\hat\imath-2\hat\jmath $. The answer given is $\arccos\frac{4}{\sqrt{65}}$. plese solve this question i am not able to solve this

homework vectors

@tpg2114 Closed..!!! ;-)

Thanks

@tpg2114 You're welcome...

Well, I was digging elsewhere (didn't notice the queues today evening)

That's why took so much time :)

@CrazyBuddy Hi! continue: I was in (rather) the same situation. I started engineering, because ( I thought) only this way I was free to study physics the way I like it, and at the end I'll have some very useful engineering insights too.

From the third year onwards, I'm taking graduate physics courses from the department of physics.

@Mostafa ah...

Well, we don't have a department for Physics or Chemistry, etc.

(which I know only after I fell into the trap) :D

3:37 PM

Really?How can it be?

Who teaches physics and math courses?

@Mostafa We have Physics & Chem labs though

(meant for freshmen people who're supposed to have those basic lab practices)

pretty boring -_-

Just wanted to say if you really love physics, don't give up and try to get into a good program for graduate school.

Anonymous

@CrazyBuddy No. Chemistry is an (applied) approximation to Physics, and Biology is just an aimless attempt to do nothing. Not always, though, when it becomes an (applied) approximation to chemistry.

@Mostafa Thanks... I'm just waiting for my UG completion. Once I finish, I'll surely get into the academia of Physics :)

@DImension10AbhimanyuPS Careful there. It's not really that easy :)

Anonymous

And Physics is the pertaining-to-our-universe part of Mathematics.

ShuklaSannidhya

3:51 PM

If the pulley is frictionless then it wouldn't rotate as the rope passes over it right?

@CrazyBuddy ?

@ShuklaSannidhya Yep

ShuklaSannidhya

Heh... Why do we make so contradicting assumptions in physics...

> Consider a frictionless pulley ... calculate the tension.

@ShuklaSannidhya Hah... We always go with the false stuff, then correct it... :P

Anonymous

4:05 PM

@ShuklaSannidhya Because it makes things look simpler.

Anonymous

E.g. Special Relativity.

Anonymous

SR is a very good approximation to GR.

4:24 PM

^^^ Me ;-)

4:53 PM

@CrazyBuddy physics.stackexchange.com/questions/77891/…

And anybody else who can vote to close

@tpg2114 Done... Thanks again :)

You might just want to take 5 mins and see if you can clear the whole queue

:)

I'd better check the review queues... :)

@tpg2114 Thought of it just now ;-)

Annoying that I'm still 271 away from being able to VtC and when I ask you to do it, you're the final vote needed... :)

Find some nice questions... Or, post one for yourself and answer it :D

4:56 PM

I seem to strike out on getting answers to questions I post

And I haven't had the time to answer very many... way too much work to do

ah.... then, be patient :P

OmnipresentAbsence

Hello people,

We all know about the FTL-neutrino mistake at the LHC. I know that SR allows for particles to travel FTL, as long as they never cross the barrier if you will. So my question is: If you have 2 seperate neutrinos, is it possible for one of them to travel slower than the speed of light and forever do so, and for the other one to travel FTL and forever do so?

5:40 PM

@ManishEarth I came across a list question (somewhere else on SE) and decided the best way to approach it was to vote on each answer that I was familiar with. Let's say 30 (up and down) votes. Will such votes be cancelled later due to some trigger?

6:25 PM

@aufkag nope

in The Pod Bay, 23 secs ago, by ManishEarth

I GOT ACCESS TO SOME COMPUTATIONAL POWER YAAAY

6:44 PM

@ManishEarth Do you need computational power because you're too lazy for computational efficiency or what?

@aufkag nah, because some things can be computationally intensive

@ManishEarth Obviously, but it is surprising that somehow your problem requires precisely what is available to you today.

?

Well, people didn't start exploring solid state physics and nonlinear dynamics that much until computers came along

@ManishEarth Still, it is surprising that any random problem is somehow just computable with today's capacity. Given that capacity increases exponentially.

It actually makes sense

people design the problems so that they can be solved with today's capacity.

They don't work on stuff they can't compute :p

6:50 PM

ie. what I do

I could very, very easily give you an example of a simple problem that is totally unsolvable using today's technology

@tpg2114 Go on.

Imagine a perfectly flat plate with a fence on it, so it would look like

__|___

And you wanted to compute the flow over the fence

Not just over the fence, just the flow in a domain around the fence like

-------------------------
| |
| |

Oops

It's not going to format

Anyway, vertical wall on a flat plate

So, is this a problem that would be perfectly computable in 2 years or will it take 100 years?

It may never be computable without models

@tpg2114 So, that's different.

6:55 PM

The number of grid cells required for DNS computation is something like Re^{9/2}

Well what they are doing is saying "We can do Re = 10 now"

And next year they do Re = 15

And the year after Re = 20

You said "totally unsolvable using today's technology", which implies that tomorrow's technology will solve it.

Quantum computers might be able to

Ah

Do you know what tomorrow's technology may bring?

I sure don't

So it's possible, but the number of cells required is astronomical so it would take a major breakthrough

For a relatively simple and useless problem

@tpg2114 But Manish isn't referring to a revolution, but rather to increasing technological ("dumb") capacity.

7:00 PM

@aufkag Well, yeah, computing solid state on a laptop is no fun

@ManishEarth I used to compute things on 25 PCs during the weekend. I thought I was at the cutting edge. :)

lol

Nah, I have access to a cluster. But I'm not using it in parallel, it's used by many people so you just select a free node and use it

I really don't know, but I suspect strongly that 25 top-notch PCs in 1992 had much less computing power than 1 smart phone today. Is that correct?

Anyways, back then, it was really important (1 weekend!) to get your computational complexity down by programming as smart as possible. I don't know if that is still the case.

@aufkag hmm. possibly.

@aufkag I know. My father has programmed in a time where you basically have one chance to get it right

You need to get it perfect, and practically no redos if there are compilation errors

Punch cards.

7:16 PM

goooooood morning

mornin'

it is 5:15am tomorrow here

Where's that??

Hey @tpg2114, I tackled that question for that other member from yesterday

@aufkag Queensland

12:46am here

7:18 PM

21:18

@ManishEarth Hey, what kind of country is that, with half hours?

@aufkag parts of Australia have that too

@UV-D I think there is a university in Australia called Manish or something like it, but my guess is that Manish isn't in Australia.

3

@tpg2114 the questioner seemed to like it

@aufkag that would be Monash

no, I know Manish is not in Australia

I was just stating that 30 minute based timezones occur in a few places

@MonashEarth

lol

7:27 PM

@UV-D I have my doubts about these half-hour people. Are they as good as normal people?

@aufkag as far as I know, most of them are okay - the ones in Australia though are from South Australia... scary place

@UV-D Never trusted them.

Will any difference allow for discrimination? (I know: yes.)

@aufkag Ummm most time zones are spaced by half an hour

Except Nepal. It is GMT+5:15 :p

@aufkag, see, as Manish shows, there is a 15 minute time zone!

@ManishEarth Well, that's just your opinion. I still think half-hours are bad.

►

7:37 PM

aaaaaaanyway, what is everyone doing? and @ManishEarth shouldn't you be getting some sleep?

/me using computational cluster

In Soviet Korea, computational cluster uses you!

►

well my ratio is a bit healthier now at 4Q's and 6A's

what to do with my bounty question - while the answers I received are good, they do not completely answer the question

@UV-D Which question?

7:50 PM

my bounty question --> physics.stackexchange.com/questions/77197/…

still has 3 days though

@UV-D Well, while of course I don't know anything about it, I see plenty of opportunity to improve grammar and formatting, which would put it right up to the top of the attention board. :)