Discussion Definition and 284 Threads

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...

definitely you can assume the premis and arrive at a truth and then consider your theorem truth only if the way from the premises to the truth result is connected by double implications. see 2 examples in the attached file

Hi Pervect, You concluded the thread titled “Another question about photon perspective, concerning entanglement” initiated by Anticitizen with this post: You also concluded the thread titled “Reference frame of Light” initiated by Klotz with this post: I am having difficulty...

I pose the question of why some are saying the end of the world is in 2012? some say we will flip, others say the north pole will fall to the side (becoming the new equator). Dave suggested i bring my question online to discuss.

Greetings, Can you recommend a website or sites that has worked examples and discussion of harmonic motion with 2+ springs in various configurations? Thanks Sparky

Hi all, I am very new to this forum so please let me know if I have posted this in the wrong place, and thanks in advance for any replies :) Backstory: My friends and I were playing a game called Portal in which you can place two portals (each of which leads to the other). We were...

The media frenzy is dying down a bit, and I'm opening this thread to discuss technical questions from researchers and students as they read this paper. I'd like the discussion to involve short questions and statements involving equations so it can be quick and conversational. The main purpose...

Just a few hours ago,I have posted a problem in the homework section.Here I want to discuss a similar problem---I mean the interpretation of the answer of a similar problem. A block is placed against a vertical wall,and another block is placed against this block.We apply a horizontal external...

A boundary value problem "discussion" So, let's say we are given a function f : [0, 1] --> R and constants a, b, and we want to find u : [0, 1] --> R such that u''(x) + f = 0 on <0, 1> with u(1) = a and u'(0) = -b. One can easily obtain the exact solution to this problem merely by using...

Dr. Ron Mallett shares his research into time travel. http://www.coasttocoastam.com/ This is highly controverial, and my understanding is that it has been shown that his solutions are not valid. A PF discussion about this: https://www.physicsforums.com/showthread.php?t=147946

I'm currently trying to pre-familiarise myself with the course on lagrangian dynamics I'll be taking in the upcoming year, by reading the course notes supplied. I'm somewhat getting the hang of it, but I could really do with some more indepth discussion about the whys and wherefores. Could...

It is a mechanics discussion regarding a problem of electrostatics. Couple of months ago I dealt with a problem:Given two electric dipoles, separated at a distance r and are perpendicular to each other.We are to find the torque exerted on each other. I took p1 as vertical and p2,right to...

Consider the following question:(this is not a homework problem,but it is one I want to discuss regarding its feature) A ball is falling onto a ground from a certain height and collides elastically and reaches the same height and the process continues.What is the averages force on the ground...

Hello, I was attending a physics discussion on fluid dynamics (fairly basics concepts) and the classic buoyancy demo came up. (A test tube is inverted and allowed to be filled with enough water to float with the volume of air trapped in the tube, the test tube is inside a larger bottle which...

He insists they are synonymous. I said I didn't agree. I told him that impedance is specifically the ratio of voltage to current in the s-domain or frequency domain. Impedance carries much more information that resistance alone. Is it technically correct to think of impedance as being the...

Homework Statement does the length of the fuse wire influence its cpacity? why? Homework Equations R=pL/a The Attempt at a Solution My teacher said no. I think it should because R depends on L Thanks for your time.

Hello. It seems from what I’ve gathered on these forums since I’ve read and posted on here, it seems there are only a few possibilities of how the original singularity came to be, which caused the big bang. Those are: 1.) Oscillating universe – The universe goes through a natural cycle of...

Science has no idea of the mechanism. All that will be said is that it just happened and because it did there was life, which continued. There is no explanation beyond that. Of course there are other explanations outside science which account for this issue, which I believe, but I cannot talk...

Today my wife and I got into a little discussion on calorie intake and weight gain. A dietitian will tell you that if you take in an extra 3500 calories a day in your food, you will gain an extra 1lb if you do not burn off that 3500 calories. This is usually true, since there is no food out...

To me, this election is over. Time to move on I must say, I am sad to see moderate Republican losing their seats because of their party affiliation. People like Lincoln Chafee deserves to have a say in the current political climate. Unfortunately, these moderates became indirect casualties of...

A workmate and I have on-going disc^H^H^H^H arguments about Physics and I need a third party to break the deadlock on the latest one. I hope you guys can help. He is of the opinion that the effect on a car driver of running into a brick wall at 60mph is the same as if he had a head-on...

The other day I was browsing a forum dealing with immortality and I read people taking their idiotic ideas to absolutely mind-bending directions. I quote: "I do fully agree with you about creating our own universe and stuff (just don't think it's going to happen any time soon). But...

Dear all, I am having a heated discussion about this web paper: http://zanket.home.att.net/" I would like you to comment my opinion that this paper is wrong already in its introduction. I reproduce here the first lines of a figure caption found in the introduction: I don't discuss...

The set of events that are simultaneous to a person moving with velocity v is the same set of events that would be occupied by a hypothetical particle moving at (c^2)/v

http://realityconditions.blogspot.com/2006/09/on-price-and-penrose-on-time-asymmetry_18.html" is a very interesting discussion of a proposal to allow backward causation in quantum mechanics. The basic idea is that the time asymmetry of QM ("collapse of the wave function") violates our...

Hello, I'm not much of a physics entrepeneur, but I was just discussing this with my friend, and hunger for a more difinitive answer came upon me: Say you design a car, and it does 0-60km/h in 2 seconds. Now say you want to redesign the car to do exactly the same results on planet Q, which...

Here's the issue in question. Let's say you had two equally sized pans filled with equal amounts of water. The only difference between them is the water in one pan is 50 degrees while the other is 100 degrees. Next, they are put on the stove with equal flame applied, would the pan with 100...

E-mail to Jan Veizer Subject: The missing link is albedo variation (Pallé et al, EOS Jan 2006) Just showing that the global warming of the previous decennium can be explained by natural factors.

Hi, I was hoping to discuss the book "Other Minds" (2001) by Avramides. Or rather : discuss the topic of other minds, and use the book as a reference (as I understand it gives an historical overview of approaches to the problem). The problem of other minds interests me a lot. I feel...

Dear vanesh, I have decided to move the anti-gravitation discussion into a new thread. At least in this regard josh is right, it's gotten a bit off-topic in the old one. For those who want to follow, discussion is about the paper http://arxiv.org/abs/gr-qc/0508013" see also...

The intent of this thread (for now) is to introduce the basic theoretic principles of rotational/vibrational spectroscopy, follow this up with a brief sketch of the expermiental techniques and finally zoom in on the experimental and theoretical aspects of a specific technique of recent interest...

A laser in visible is used in Raman spectroscopy and the resultant spectrum is in IR and Microwave region(which means molecular vibrations and rotations are excited), what type of interaction is this that induces these levels? ( I cannot think more than..."To be Raman active molecules should...

I posted this in a newbie thread and no one has gotten it. Come on, I know there are members out there that know this stuff. This is a PF scavenger hunt. You can search PF for the answers if you don't already know them. I'll bet BobG nails this one. 1) What did tribdog do to his...

Hi. I have a problem with a statement that was in the first chapter of my "World Religions" book for school. It first explains that the word "God" can have many different meanings. It then concludes the chapter with "It is a fact, not a mystery, that God, whatever or whoever God might be...

I need help writing a discussion for the biology lab report that I'm doing. If anyone could help in explaining the results it would be much appriciated. Here's the experiment... We had 6 flasks each containing yeast, sugar and water. 2 of the six we added 5ml of 1.0 M HCl and into two others...

Relative Velocity? OK - I'm having problems visualizing a relative velocity problem. Please let me know if I am on the right track... problem involves a jet with initial V of 300 mi/h due east that encounters winds at 100 mi/h in a direction 30 degrees north of east. I need to calculate new...

Hey everyone, I am new to these forums and want to make it clear up-front that I am coming from a revolutionary Marxist-Leninist-Maoist perspective. The philosophy that I uphold is very much in line with the point that Karl Marx made that "the various philosophers have interpreted the world...

I'm not endorsing Heim theory, which is described here: http://en.wikipedia.org/wiki/Heim_theory But, I am interested in what anyone has to say about it.

Has anyone read Motion Mountain? If so, how good is it? :smile: