Discussion Definition and 265 Threads

hello there, I have started to tackle the giant book Gravitation by MTW on my own. I would like to see how you people who are having fun in reading this masterpiece faring in solving the exercises. I have read some books on tensor analysis and differential geometry and spacetime geometry as a...

Discussion continued from this post on another thread... Bell's proof does not involve any notions of "particles" or "waves" whatsoever, it only involves observed experimental results combined with the idea that the theory generating them is local realistic. Again, do you agree or disagree...

This started in the MIT professor's thread. But this part is concentrated on Faradays and Lenz law in constant magnetic flux loop and transformer that is very interesting and not quite relate to the MIT professor discussion. I want to bring this out and continue discussion about the Faraday's...

Hi, I'm currently studying GR from Wald's book. The book is fine, but I want to know more details about the collapse of stars, e.g., more about white dwarfs, neutron stars, mass limits, the use of Fermi-Dirac statistics in this cases, etc. What book, paper or website would you recommend?. (I'm...

Seeing as the test day for the 2011 Pascal Contest was yesterday, let's discuss! My answers: B>E>C>B>A A>B>D>E>C E>D>A>C>A D>A>C>E>D D>C>B>A>C Now I was not sure about problems 20,24, and 25 If anyone remembers the wording of the problems, can you please post them? In fact, can anyone...

Does anyone know of any history forums run along the lines of pf?

I would like to start a discussion involving how sound works. I've read plenty of websites but none can satisfy the level of curiosity I have. To get started I would like to know what it means for low frequency to travel farther than a high frequency all sound waves travel the same speed? The...

Hi all, Since it has been sort of a tradition to open these kind of threads, i thought i might open this one so everyone can post things related to REU's. Like, which REU's you are applying to, and the like.Personally, I am still in the process of searching for potential REU's. So far, I have...

this is from chapter 4 of university physics of young and freedman q19 why can it hurt your foot more to kick a big rock than a small pebble? must the big rock hurt more? explain? but I can't see the answer at all by just applying Newtons law in the scenario of the small pebble mp is small...

Hi Guys and girls First have very little knowledge of this stuff, but watched a tv program today that made my head spin a little bit. The threads I have read on this forum make it spin a little more, so I'd like to just post my question and hope there is a simple answer. The program I...

So there is this work-energy problem online that I was discussing with a friend. We both concluded with different answers and I 99.99% sure that I am correct, but there is that 0.01% chance that my understanding of physics has been completely wrong over the years. The problem is simple: A...

Alright, am I the only one that hates discussing if something is "Possible"? In effect, you can say that anything is possible because you can never 100% prove that something is impossible. (I can't 100% gurantee that gravity won't turn off tomorrow, I just have no reason to believe it because...

How did you feel when you found out that there wasn't really a Santa Claus, if you ever believed there was?

I have always wondered the criteria behind choosing between SRAMs and DRAMs. I know a few of them- like SPEED, POWER, SPACE, etc. But how do we know which one has to be prioritized? In case of Space, DRAM wins, but loses in Speed of operation. Though DRAMs are less power consuming than SRAMs...

Please excuse me if I seem inexperienced (I am new to this forum), but lately I've been thinking a lot about a length contraction paradox called the Barn-Pole Paradox. The paradox: A pole and a barn are both at rest relative to each other. When both are at rest, the pole is slightly longer...

EDIT: We are looking for someone to clear things up for us! An engineer friend of mine and I are having a debate about heat vs cold. Basically I am saying you can't 'add cold' to a system you can only add or take away heat and for some reason he is disagreeing. Chat of Gchat/AIM ****...

I can probably argue against evolution without biblical references? Anyone wish to hear my argument?

all are open to those who like to brain storming like me in physics question...i'm a physics degree student...and you are please welcome and try and comment to me if any... 1. inside an just used oven the temperature is 200*c... you can put your hand into the oven without and injury you got...

I am a beginner with respect to MOSFETs and have just begun studying them at college 2 weeks back. What I am actually struggling with is the basic functional differences between MOSFETs and JFETs. Two of them are- dielectric and substrate, both of which are there in MOSFETs. However, I...

I've only taken an introduction to physics classes so excuse any ignorance on my part. Recently, I've been wondering why all we have figured out is an indirect way to harness the energy of heat. My reference is to nuclear power mostly; We use the enormous amounts of heat to create steam from...

As you might know, the 2010 Euclid Contest was officially taken yesterday. So let's discuss! I thought it wasnt too bad. #10 was hard though (the triangle one). Here was the question: For each positive integer n, let T(n) be the number of triangles with integer side lengths, positive area...

Ok, I've looked a bit into your Posts. The problem is, I suck at math (i.e. differential geometry). So please tell me if I got the basics right (your post #6): The Minkowski basis vetors are \partial_t,\partial_r,\partial_\theta,\partial_\phi, with length 1,1,r,r \, \sin(\theta)...

It should be noted MotoH started this thread. Posts were merged from other threads which inadvertantly put one of mine on top. Heck, front-wheel drive ruined much of it for me. What fun is driving without the occasional power slide? I was as comfortable driving a car sideways as forward...

Greetings, In Feynman's lectures - vol. 2 either chap 19, 21 or 23 - I think 23 (I'm at work and don't have the lectures here), Feynman shows in a capacitor that a changing E-Field induces a B-field, then he shows that the B-field induces a new E-Field (he calculates the E-field) and then...

Czes discussion re Compton wavelength and new Smolin paper These are posts from the bibliography thread (which has enough to do just listing the new papers, without discussing them :biggrin:)

Can someone tell me how long these computer internet forums have been in action on planet earth? When I turn on a light bulb...light waves are produced..are photons "created" or emitted by flowing electrons and if so what causes the electron to do so..or what is the mechanism "inside" the...

Hi everyone, I've just finished year 11 here in Australia and I've been reading some notes on abstract algebra just out of curiosity. I have had a little difficulty grasping the concepts, and I've read up on some linear algebra (up to the point of Euclidean n-space - haven't yet read about...

What differentiates the sound of a tree falling from the sound of a piano playing? What differentiates the sound of a piano (near-universally classified as music) from the sound of a rapper (still argument about naming that music)?

How did you feel when you found out that there was no Santa Claus (if you ever believed)?

As promised in the now closed CRU-hack thread, this is intended to show why I am convinced that the cause for global warming is overstated and that changes in use of fossil fuel and CO2 production will have little effect on climate. I will try and stick to the scientific method, no room for...

Is it a photon that gives rise to an electron ?? Photon , in presence of any external force that disrupts its magnetic and electric field balance in space where E/B!= c causes production of a pair particle -- electron and positron . I have done a lot work upon it .Want to know other's view...

A Discussion of "Existence". I have been reading these forums for many days and recently decided to make an account. I have read a vast array of topics ranging from Quantum Physics/Mechanics to Transcendentalism, to Buddhism and I have also learned of some new philosophies. I figure expanding...

Hi, I'm currently one of the organizers of a seminar for talented high school students in my home town and one my task for the next session is to give a brief talk on some interesting subject in (theoretical) physics, with a discussion afterwards, where the students will participate. It...

anyone can help me about solar energy, discussion only.,tnx

I'm starting this thread to continue a tangential discussion of interpretations, specifically Bohmian vs Copenhagen from https://www.physicsforums.com/showthread.php?t=324790". As a class of phenomena "Yes" of course. As an object "No", nor do I believe in the existence of "The Universe" as a...

I am sure a few people have a Quantum Design PPMS. Is anyone else here actively involved in building custom options, and writing custom software, or simply has a lot of experience with it. Quantum Design is (maybe naturally) cautious about giving out blueprints of the sample chamber and such...

Not too sure if this is the right place to post... any good optics discussion forum that one could go to? any recommendation? Thanks

This seemed appropriate material for this Forum, I wasn't sure what section. :-p http://www.bryanappleyard.com/blog/2008/04/teaching-maths.php

A common misconception from friends studying outside a Bsc. is the impression that our universe is expanding out in space, that space is infinite and that simply matter traverses into voids. They seem to have a hard time understand that the expanding universe is space itself expanding and that...

Just started a Linear Algebra type math class this semester, and for some reason it has a 2 hour discussion class once a week. So far we have only meet 4 times so far, and i hated going to them since the 2nd meeting The TA goes over the same examples that the professor gives during lecture, and...

Being from Kansas, I thought a little discussion on this one might be appropriate. Looks like the space shuttle piggy-backed to me. http://www.kansascity.com/news/breaking_news/story/1025246.html" http://media.kansascity.com/smedia/2009/02/09/13/ufo2.embedded.prod_affiliate.81.jpg

Homework Statement We did this roller coaster lab where we had a metal marble roll up and down this roller coaster track. One of the questions he asked us was "is energy "missing?" explain where it went." I know friction takes some of it, but I am not good at wording it right to sound...

Homework Statement True or False: To raise a 2.3kg mass from its resting place on a table, more work is done by lifting it diagonally than lifting it straight up. Homework Equations w=fd The Attempt at a Solution True: I argued that although the same amount of force is being...

Hello, This morning, I was reading some stuff about DNA Computing on wiki, arstechnica, and other places.. I found it quite interesting and want to know the latest happening in the same area. If any of you is working on this new technology then please let's discuss about it. Thanks

Im not sure if this is the proper area for this but when they say that there might be other dimensions that we don't no about are they referring to more than xyz? i mean how could something have another dimension, it seems weird to think about. Just looking for someone who has some insight on...

I find that Chapter 3(Linear Algebra) in Boas is not very clear in certain areas. Could someone please recommend a book which does so more clearly?

Continuing the Dopfer discussion from other thread: Well of course there would be a pattern when you change from a near field experiment (Dopher) to a far field experiment (pinholes) you get different results from an entirely different experiment. There is no “In This Case” as there is no...

Ivanhoe and Isaac became pirates a long time ago. Both of them run for the position of captain. Everybody slips his envelop in the box one after the other. Ivanhoe receives P votes, and Isaac receives Q votes. Assuming P>Q, what is the probability for Ivanhoe to lead during the entire voting...

I wonder, if you tie a string to a stone and spin it around, does the string that is closer to your hand move faster than the string that is tied to the stone? *EDIT* This question leads to a much greater topic of discussion, and the reason for leading off with this question is because the...

"So You Want To Be A Physicist" Discussion Discussion on the article https://www.physicsforums.com/showthread.php?t=240792" by ZapperZ Comments, suggestions, questions are welcome. The series has almost reached the end of its intended purpose. At this point, I'm looking over it to plug...