Explain Definition and 1000 Threads

Hi all, I'm hoping a pretty simple question. When I read about researchers working on galaxy surveys, they often state they're working on "XX-band selected galaxies". For example, D.J.B. Smith et al. performed analysis on a large number of 250μm-selected galaxies at z < 0.5. Is this as...

I did not understand the Intermediate Value Theorem explained today in class. The professor did not even go to his office hours :(.Use the intermediate Value to show that there is a root of the given equation in the specified interval. #51 in Stewart's Calculus 7th ed. (section 1.8) x^4 + x -...

Matter can not be created nor destroyed..."in a closed system" ...and except where "energy transfers" are present. So, in a fusion reaction, energy is released; but mass is also lost. ? Can someone/s just square this more a layman (me) so I can understand exactly what's going on? Thanks! Max

Can anyone explain this excerpt to me? I'm lost on how the positive and negative charges push each other away instead of attract. Thanks! P.s I think this goes in this forum.

Referring to the attached image. i seem to have forgotten this material and am trying to revise, how/why does it become $\frac{1}{2}$ $(\sin(z))^2 $' ? and does the path $C$ that we are given come into play in the solution? Sorry for the noobness, any help is appreciated!

Hi, In Spice, the capacitance between two points x, y is defined as follows: Cxy = - dQx / dVy for x != y Cxx = dQx/dVx Could anyone help me explain why it is defined like that? I know that C = dQ/dV but the formula above seems strange to me. Is my understanding below correct? Cxy =...

Hello, I am trying to get into amateur astronomy but first I have to understand the sky. Because of the tilt of the earth, there is more than half the surface area of the Earth radiated by the sun's rays and therefore those areas which are on the hemisphere of more sunlight have longer days...

Can someone please explain to me what a "dynamical trajectory" means? I am reviewing the first chapter of my classical mechanics book (Fetter & Walecka), and in the very first section he uses the term "dynamical trajectory". I have seen this derivation many times, but I just don't understand...

Hi, The violation of Bell's inequality says that quantum mechanics can't be both local and realistic. Let's assume it is realistic but non-local. How does this explain the fact that a single particle can be in a superposition that collapses to a particular state when measured? Since we only...

Homework Statement An integer sequence has cropped up in research I'm doing, but I'm having trouble understanding it. A number n is on this integer sequence if there is no m>0 such that n+m is divisible by 6m-1, 6m+1, 8m-1 or 8m+1. http://oeis.org/A109598 What I'm wondering is if...

Hi, I'm not a scientist, but a documentary filmmaker doing research on the nature of reality. An essential disclaimer as my question might seem a bit superficial to most you guys who work in the field. I would like to know how the pilot wave theory to quantum mechanics explains the double...

I'm on my second year in college and I'm doing a lecture on Fermi levels. The descriptions on Wikipedia and other sites don't seem to have been made for my level of knowledge, as I have difficulty understanding it. How would you describe Fermi levels on an entry level?

I'm trying to cross check mathematically the mA being discharged from a .33uF capacitor which is charged to about 1200V by a circuit (see single_circuit.jpg) which is provided 37W of power to it. I do it three ways. 1) The circuit draws 35W total. 13V @ 5A = 65W. But the power supply drops...

Here are the links http://books.google.ca/books?id=RN4_jLbVO3YC&pg=PA50&dq=Stirling+auto+engine+a+lot+of+progress,+but+Spirit&redir_esc=y#v=onepage&q&f=true http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880002196_1988002196.pdf I have read both but I don't understand how the gas...

hi i am not a physicist, i am not even sure if this is physics related, and sorry if i haven't posted this in correct place! just out of curiosity was wondering if this makes sense? this guy i know posted this diagram, just wondering if anyone could tell me if they know what it is if it even...

Sorry in advance for this probably stupid question. If there is entanglement is there not entaglement for all particles. If so, could there not be entanglement for the Higgs boson, and therefore our own gravity, could have an equal and opposite force, both combining for a net effect of...

Could you please help me by suggesting some books that tell the story of how "stuff" ( I mean the stuff we discuss in physics ) such as origin of matter from a universe with nothing but energy, origins of wave, gravity, electromagnetic forces etc in the course of the evolution of cosmos after...

Can someone explain this please?? Weird pulley with Tension Homework Statement See attached picture for problem Homework Equations n/a The Attempt at a Solution The answer is B. No idea why. Any help would be appreciated. Thanks!

In regards to the famous experiment where a magnet is put under a sheet of paper with iron shavings on top, i don't understand why they distribute according to the shape of the magnetic lines of flux. (as seen in the link below)...

Why is the magnetic flux density uniform at the center of the circular loop ?

I know that a beam suspended in two ends can have many modal shapes. However, when it comes to unsupported free beam its first three eigenfrequencies are 0, why? And why should it have eigenfrequencies at all if it is free to move? Is eigenfrequency characteristic of every material? Why is it...

I don't have any big programs. I just write programs to get me through my math classes. But I want to have the output look pretty. Like one program I have is for my finance class. prompt p if p = 1 then Prompt b,r,n,t r/100→x b/(1+x/n)^(n*t)→l disp l else Prompt b,r,n,t r/100 →...

So I am trying to learn this. It is not making sense to me. Every single resource I have found tells me I need to make some weird substitution, and then it becomes a differential equation that has the Airy equation as a solution, and then skips to finding the energy eigenvalues as a function of...

I was wondering if there are any theories that show how much mass the higgs field gives to each particle and why? I am specifically wondering about the observed masses for each particles rest mass. Does the higgs mechanism give mass in quanta, and if so is there a reason for the amounts?

I have the code (space = _): def recursion0(x): ____if x == 1: ________return 1 ____else: ________recursion0(x-1) ________print x I know values 2-x will print, but I cannot figure out how to map the call stack. Below are my thoughts. Let's set x = 3. 3 goes to 2 in...

Most of the paradoxes are solved by either "Relativity of simultaneity" or "Born rigidity" And there is a 3rd tool that i know is "Minkowsky spacetime diagram" But i do not understand how clear/imaginable it will be when you represent a paradoxical event on Mink Sp Diagram (MSD) When i asked...

Recently (or a few weeks ago), I've started to take interest in the idea of relativity but after watching many videos and reading a couple of websites, I still don't think that I really understand it. I'm probably not suppose to understand it (or at least not yet) considering that I'm still...

The title says it all. Commutative* sorry Mod note: fixed title.

Hamming distance satisfies the triangle inequity that is for all x, y, u in c such that d(x,y) <= d(x,u) + d(u,y) where c is a code. Also when does the equality hold? My approach is Turning x to u by changing at most d(x,u) letters and turning u to y by changing at most d(u,y) letters. So...

#include<stdio.h> void main() { char c[]="gate2011"; char *p=c; printf("%s",p+p[3]-p[1]); }

I am posting here because this is NOT homework. Problems are finished. However we have an exam on friday for calculus 1 class and well... I've been trying real hard to understand it but professor has a real strong accent and he speaks too low, no one can hear a thing! Anyway, we did the...

The title says it all. I'm sorry if you get annoyed because of my "noobishness", but I'm still a physicist in training (taking undergrad Classical Mechs). I'm really interested in Quantum Theory and I keep hearing about Quantum Field Theory, but not a single website accurately explains what it...

Please see the attached image. There are 6 figures. Please explain the proofs for sin(90 - θ) w.r.t the 2nd, 3rd and 4th images. I understand the proof w.r.t 1st image. In the 2nd image y1 and x is negative. In 3rd image y, y1, x, x1 are all negative and in the 4th image y and x1 are...

In Spivak's Calculus, Chapter 1, pg 12, theorem 1, it says that in order to prove that theorem: |a + b| <= |a| + |b|...there are 4 cases of what could happen...blah, blah. So one of the cases supposes that a >= 0 and b <= 0. Then it goes on to say something like "In this case, we must prove...

Its the attached picture. I'm not seeing why when using the dot product, they start using sin.

all objects travel at a speed .when we come to light , the speed is approximately 3 * 108 . i am confused about how can it travel with such a speed . i have surfed in the internet but it only says that it is not yet proved . i wish to know the answer . this could help me to study optics more...

I was looking at the wikipedia article about cosmic inflation (you know, the first 10-32 seconds). It says that an inflation hypothesis is a neat way to explain a number of otherwise puzzling observations, but it doesn't say much about what would make inflation occur and it doesn't mention...

Hi, Please explain why z = cosθ + jsinθ in this video at 41:13 http://www.youtube.com/watch?v=OvDePn41fPY&list=SP854AA255B15C574C&index=2#t=39m46

Homework Statement Explain in your own words what: lim f(x) = 5 x→2 means. Homework Equations None The Attempt at a Solution I wrote: "As x approaches 2, the limit of the function f(x) is 5 (in other words, f(x) approaches 5). The value of the function that is...

Does gravity have a limited range in which it can attract objects? I looked up on google, most people are saying it's infinite.. if it really is infinite then I'm confused, because if the denominator is infinite, then the result is just zero.. and in gravity's law F=[g(m1m2)] / r^2 .. if r is so...

I am venturing in the realm of probability and I came across a concept that I call partial dependence. IE, it is a set of a events which a neither independent nor dependent on each other. They fall somewhere "in between". I have looked on the internet and I really don't understand the...

Hello. I found it very strange that matter behave as a wave and started thinking a lot... I have seen a video previously explaining this experiment and when I saw this: In red is the first path and in blue the second path. Could it be the answer? At the end of the video, in the screen of...

Why does the cross product produce a vector and why is that vector perpendicular to the other vectors? I understand how to calculate a cross product, but why for instance is the cross products of two vectors another vector that is perpendicular to it. Can you prove or explain this to me in...

I already know the definition.The limit of f(x) as x approaches p from above is L if, for every ε > 0, there exists a δ > 0 such that |f(x) − L| < ε whenever 0 < |x − p |< δ. However if this definition of a limit explains the behavior of a function around a point why is the inequality |f(x)...

Hi, I'm going to be a senior in high school this coming year. I want to ask what exactly energy is and if it is physical? I know that we cannot see with our naked eye what energy is, but is it something physical and microscopic? What is it like? Thank you very much.

Can someone explain the "cognitive" logic of the math here? I find it impossible to concentrate or learn math without understanding the underlying meaning as much 'physically' as possible (I wonder if that's a problem or a virtue by the way). I had to prove that 1/P(A) + 1/(P(A') >= 4 given...

See attached scanned pages of page 118(left side) and page 125(right side) of Antenna Theory by Balanis. On the left side, it is just some basic EM where \nabla\times \vec E=-\frac{\partial \vec B}{\partial t}\;\Rightarrow\;\vec E=-\nabla V-\frac{\partial \vec A}{\partial t} Then to Lorentz...

The title might be confusing. Anyway while preparing for a seminar I made a statement, " Absolute space does not explain the inertial forces, since they are related to acceleration with respect to anyone of the inertial frame". Is this statement correct? Please explain with few examples, Thank you..

Hi, Could you help me to understand the following expansion I found in a book of qunatum mechanics. |1+a|^2=1+a+a*+... where a* is the complex conjugate of a

I was reading about Galileo's gravity and there I came across the formula. F= -mg. Galileo said that Force is proportional to mass but in the opposite direction. I don't want to discuss whether he was right or wrong. I just want to ask that when he replaced the proportionality sign and...