Explanation Definition and 961 Threads

I'm having a bit of a problem getting my head around Olber's paradox. The explanations haven't convinced me (I'm sure the fault is with me). According to Wikipedia: "To show this, we divide the universe into a series of concentric shells, 1 light year thick (say). Thus, a certain number of...

I am currently studying antenna's and the concept of reflected waves and reflected power inside conductors really confuses me. When I imagine an AC current flow inside a conductor I imagine all the electrons to have an equilibrium position before the AC voltage is applied, and then once it is...

I am studying general relativity and quantum physics at the moment and as you know each theory has a different explanation for gravity and now the string theory has a different one too (afaik) so what is most likely to be the actual explanation of gravity? General relativity seems very logical...

Hello All, I was recently looking into explanations for the operation of Faraday's unipolar generator and came across the following article, titled "The Unipolar Generator, A Demonstration of Special Relativity" published by a professor at the University of Maryland...

many transition elements have variable oxidation state like Fe.what is the exact cause for this?they may not obey the octet rule,but what is the reason behind this?Also,elements like nitrogen are not transition elements and still show variable valency.what will be the electronic configuration of...

Hi can anyone explain what a quadratic divergence is? and if so how it effects the mass of the scalar field i.e why m^2 = m^2_{0} + \delta m^2, why are these things squared? Also how would this divergence affect the standard model as a natural concept, because from reading books it would...

Galileo showed that, if air resistance is neglected, the ranges for projectiles whose angles of projection exceed or fall short of 45 degree by the same amount are equal. Prove Galileo’s result. Answer in my textbook : set θ=45+ - ∂ (I understand this) Now comes the weird part R =...

Homework Statement This isn't a specific problem, but more of a type of problem I do not get. I am taking undergrad complex analysis, using the book by Bak and Newman. Its only a couple week in and I am having to spend a lot of time on it, last week I spent about 7 hours on the homework (which...

I have read a lot of articles on pulse width modulation and I am none the wiser as to how it generates different voltages by simply varying the pulse width of the waveform. What I read was that if you have a rectangular wave train of some amplitude and change the 'ON' period the "NET" voltage...

Work (J) =\int Force(N) .dx(m) I understand this one, work done = force * distance moved in direction due force, but the force can change in magnitude or direction so less/more component of the force is in the direction of movement, so in this case the area under the graph of force vs distance...

Problem: The general idea makes sense intuitively to me, but most sources I've found cite Pascal's Law merely as scientific fact with not much explanation. What I'm wondering is why pressure applied at one point in a fluid is transmitted undiminished to all other points? Is it a concept due...

This vid was produced by Cal Tech. Pay attention to Dr. David Goodstein's explanation of the polarization of light near the end of the video. Does any of it make sense to you, or are Cal Tech Professors showing their fallible sides?

Hi all, new to the forum here. I posted this about a week ago on a different web board and had difficulty understanding the reply. I was hoping I might be able to ask someone here if they can help me make sense of this... I'm amazed at how much trouble I'm having with it... The Problem: If...

This is taken from "Passage to Abstract Mathematics," Watkins and Meyer. "Theorem 2.3.9 (Division Algorithm) If a \in\mathbb{Z} and b\in\mathbb{N}, then there exist q,r \in\mathbb{Z} such that a = qb+r and 0 \leq r < b. Furthermore, for each b\in\mathbb{N}, this representation of a is unique...

This guy relates the calculus chain rule to a popular mob movie. You should really check it out. This is one of the newer videos but people like the way this guy explains things. Here is the link: Ghetto Dude Relates Calculus Chain Rule To "THE MOB" - YouTube

Homework Statement The filament of the lamp in X breaks and the lamp no longer conducts. It is observed that the voltmeter reading decreased and the lamp Y glows more brightly. a) Explain without calculation why the voltmeter reading decreases. b) Explain without calculation why the lamp Y...

In SR, pure relative velocity between two observers causes a time dilation between them. It seems that if the two observers were at rest w.r.t. each other at some point in time, then the one who accelerates to achieve the relative velocity is the one who gets time dilation (i.e. comparatively...

I can not seem to find out what a wave function function is amd I would just like a simple explination of what it is and how it is used. And what is this symbol ψ. Thank you.

Hello Could anyone give an intuitive explanation of the determinant? I know mostly what the determinant means and I can calculate it etc. But I have never got any real-world intuitive explanation of the general formula of the determinant? How is the formula derived? Where does it come...

I'm taking my first course in Analysis, and we learned a couple of theorems about Uniform Continuity. I have been able to visualize most of what's been going on before, but I need some help with the following: E \subseteq ℝ, f: E \rightarrow ℝ uniform continuous. if a sequence xn is Cauchy...

Can someone please explain to me, in as simple words as possible, what a quotient group is? I hate my books explanation, and I would love it if someone can tell me what it is in english?

If you had a possible explanation on dark energy... As the title tries to suggest, what would be the best way to get opinions on my idea of dark energy, without sounding like a kook? I spend probably spend 2-10 hrs a day either thinking, reading or watching documentaries about the cosmos. I...

I've been reading a few mathematical definitions and I'm still not sure I grasp their significance. If Ax = b, then what do the singular values of A represent in terms of x and b? Why are they important? I'm not looking for a formal definition, just a conceptual description or even some...

In the following two problems I am trying to get a deeper intuition of, the plane has 3 variables and is 3 dimensional and the hyperplane has four variables and is 3 dimensional as well. Can someone please show me why, practically, in the context of these problems? Question with hyperplane...

In trying to get the Aharonov-effect right I've found something that I'm not sure how to sort out. Briefly put my understanding of the effect is that it shows something that cannot be explained by classical physics in the sense that makes observable a classical EM global gauge transformation...

Homework Statement Calculate the eigenvalues of the matrix 5 2 -3 0 Homework Equations The Attempt at a Solution Ok we were taught that eigenvalues were calculated by taking the determinant( A - λI) = 0. So just subtract a "λ" value from the diagnol entries of the given...

For example, dividing by 2, means we cut something in two. But dividing by 0.5, can only be explained with multiplying something by 2. So, is there a "physical" explanation of dividing by 0.5? Is it "I divide by an entity that internally multiplies' or something as so bizarre?

Hi, I am trying to get an idea of what a quantum simulator is. I know that it has to do with quantum computers and information theory, and it basically represents a model, but has anybody have something like a textbook definition or the title of a book where i can look it up? Any help?

Homework Statement If two forces of equal magnitude act on an object that is hinged at a pivot, the force acting farther from the pivot must produce the greater torque about the pivot. a. False b. unable to decide without knowing shape of object c. True Homework Equations T=rxF...

Hi. In Apostol's book "Introduction to analytic number theory", Teorem 3.2(b), Apostol proves (1) \zeta (s) = \lim\limits_{x \to \infty} \left\{ \sum\limits_{n \leq x} \frac{1}{n^s} - \frac{x^{1-s}}{1-s} \right\} for s in critical strip. I know this translates to a Mellin transform...

Homework Statement http://em.groups.et.byu.net/embook/ch6/mod6.4.html ^^The link has the problem Homework Equations The Attempt at a Solution I know the answer is (a), but can someone explain to me the reason configuration (A) induces the largest V emf?? compared to (b) or (c)??

I'm trying to explain Gauss' Law to a bunch of high school kids. They want to know why the total electric flux through a closed surface does not depend on the shape and volume of the closed surface and the orientation of the enclosed charges. I know the math, but conceptually, I'm at a...

My book talks about it, but doesn't give a very intuitive reason why. It essentially says that from a modified version of Liouville's Theorem, the electrons in a band stay in that band. Then it says the phase space (position-wavevector phase space) has a constant density through time, and if...

In Bernoulli's equation, why the work on fluid at the lower end of the pipe is taken as negative? please explain why the force is negative to displacement at the lower end?

Greetings friends, I'm an engineering student and I currently work in a restaurant and I've observed a beautifully interesting phenomena while washing the dishes in the stainless steel sink. I'm very interested as to what causes it. While I'm drying dishes that have just been passed...

Gravitational Field Paradox Explanation?? Hi everyone. If electric and gravitational field has an infinite nature-meaning that the effect one charged particle has on another charged particle always remains even though it diminishes over distances but can never reach absolute 0-then how is this...

Why is the E[ Y - f(x) ]^2 minimized when choosing f(x) = E[Y|X] ?

Please, I need you to teach me how to write the equations from the Karnaugh map and then how to draw the NAND circuits. Here's the sample that I have but I don't understand :( I know the basic of writing SOP and POS from the Karnaugh map but that's all. I don't get how it is converted to get the...

Hi all, I'm looking for some help in understanding one of the theorems stated in section 20 of Munkres. The theorem is as follows: The uniform topology on ##\mathbb{R}^J## (where ##J## is some arbitrary index set) is finer than the product topology and coarser than the box topology; these...

For every force exerted by object A on object B, an equal and opposing force is exerted by object B on object A. I need help understanding the principle. I understand it when dealing with a completely stationary object: pushing on a solid wall, it exerts an equal force back to your hand...

Hi people, I'm new here, so, if there's anything wrong with my post, please tell-me =) So, if we have a recipient, with a cavity and a small hole, and imagine that we have a sudden expansion of the gas inside the recipient(we assume the volume increase was ΔV, and the duration of the...

Hi All, The question is rather simple: Why a plane mirror image exchanges right with left but does not interfere with up and down? Best wishes, DaTario

Hello All, I am new to GR, studying slowly. I am little bit confused between the following terms and their usage: (a) Co & contra variant vectors - Do they help in transformation? (b) What is a co-ordinate free system? Do co & contra variant vectors help it? (c) What is parallel...

Hello, Why people use semi-log and log-log plots? What are they advantage? Linear plots are more convenient as they show the direct relationship between x and y variables, aren't they? Thanks.

1. Question: Find the directional derivatives of f(x, y, z) = x2+2xyz−yz2 at (1, 1, 2) in the directions parallel to the line (x−1)/2 = y − 1 = (z−2)/-3. 2. Solution: We have ∇f = (2x + 2yz)i + (2xz - z2)j + (2xy - 2yz)k. Therefore, ∇f(1, 1, 2) = 6i - 2k. The given line is...

Hey all, I was wondering if someone could explain the difference between isothermal and adiabatic processes. I know that in isothermal process, there is no temperature change in the system, and in adiabatic process, there is no heat transfer. However, can someone explain to me what each one is...

Homework Statement If the magnitude of the Earth's momentum is P, what is the magnitude of the impulse that the sun applies to the Earth during six months? Homework Equations The Attempt at a Solution I know the solution is 2P, and I'm pretty sure it's just due to the change in...

The derivative of sin(ax²) is 2axcos(ax²). Why is that? I understand the cos(ax²) part of the derivative but I don't understand where the 2ax is coming from.

I wish to know why and how does hysteresis occur from a purely mathematical perspective, using analytical functions and multivariable calculus. Thank you!

I need explanations at the last part of this math solution. Question: Solve the differential equation: y' = (1 + 2/x)y Answer: ln|y| = x+ln(x^2)+c |y| = e^c.x^2.e^x y = Cx^2.e^x (C = +/-e^c is any constant that is not equals to 0) What I don't understand is this part where ...