Origin Definition and 651 Threads

If a substance gains energy, it's molecules vibrate faster and thus the material increases temperature. My question is if heat lost through any other means but radiation is zero, how exactly does these molecules radiate photons?

In a previous thread it was concluded that both torque and angular momentum are taken about a chosen origin, and these quantities are generally not invariant under translations of the origin (since ##\vec{r}## changes but ##\vec{v}## does not, etc.). The moment of inertia tensor doesn't...

I often read that whenever a new fossil is found (like a bone fragment or skull fragment etc) they trace it back to either some animal or human , now mostly (and before DNA testing was possible) this was done I suppose by visual inspection and "radiocarbon" dating to put the fossil in a...

Hi everyone, I am confused in this question. First I solved it by noticing that the gradient of the function will be zero (without substitution the hit) I got that it's a conservative field so the integral should be zero since it's closed path. Then I solved it by the hit and convert it as any...

Can email spammers alter email headers so that we can't find out which internet service provider and mail server originates their messages? Sometimes emails sent from a reputable ISP get temporarily blocked by some servers due to complaints about spam originating from the ISP. The sender is...

Summary: So we are just going to ignore the distance between C and the left support point (-D/2)? If the origin is at C, doesn't this mean M is -D/2 from the origin? In the evaluation, they clearly acknowledged that there is a distance between C and xp which is (-D/2)...

Hi, This question just came to my mind and I thought I should confirm it. Are the cosine functions with the same amplitude but different frequencies are totally in phase at any other point other than the origin? The frequency, f, could be anywhere between 0 < f < ∞. I'm sorry if the answer is...

The problem is: Solve the time independent Schrodinger Equation for infinite square well centered at origin. Show that the energy is same as in the original case(well between x=0 and x=L). Also show that the solution to the this case can be obtained by setting x to x-L/2 in ##\psi## in the...

Summary: Potential at origin of an infinite set of point charges with charge (4^n)q and distance (3^n)a along x-axis where n starts at 1. From V=q/r, we find Vtotal=sum from 1 to infinity of (4/3)^n(q/a), which diverges. There cannot be infinite potential because there is a finite electric...

I'm not really sure how to do this. Maybe somehow I should transform the density function. Can you give me a hint?

Below I refer to the following article: The Weight of the World Is Quantum Chromodynamics Andreas S. Kronfeld Science 21 November 2008 Vol.: 322, Issue 5905 - pp. 1198-1199 I've been trying to find more information on the subject but it's been hard for a Google peasant like myself. Just the...

As I understand it, plasmids, like mitochondria, have their own genetic material and are capable of self-replication. According to Wikipedia: Plasmids are considered replicons, units of DNA capable of replicating autonomously within a suitable host. However, like viruses, they are not...

This Science magazine News article discusses a new scenario for early Earth history that is claimed to explain the Earth's surface metal distribution and that it could effect conditions affecting the origin of life. This was before the end of the heavy late bombardment (timeline diagram in...

This is my first video!

Homework Statement (Problems/diagrams referenced are attached as images.) Homework Equations Net torque about an origin = time derivative of the angular momentum vector about the same origin. The Attempt at a Solution I've solved these problems before, but I'm now looking back at them and...

I am searching sources, which would express purely (without any other expression on how the data was obtained, etc.) elementary origins of the universe. As we would have certain artistic visualisation on how our Mars rover would operate on landing on mars, are there sources which give data on...

Homework Statement Under the influence of a central force F(r), a particle of mass m is observed to move in an elliptical orbit centered at the origin (the force center is not at one of the foci, as would be the case for a gravitational orbit) a.) Show that the polar equation has the form 1/r =...

https://www.sciencealert.com/matehmatical-model-of-cold-dark-matter-bose-einstein-condensate-stars Interesting read. Thoughts and comments?

Homework Statement A particle (5 kg) moves with constant velocity 2 m/s along the straight line 2y=3x+4, the angular momentum of the particle about origin is? Homework Equations L=r x p The Attempt at a Solution For a 2d problem we take the component of velocity perpendicular to the point...

Homework Statement Hello everyone, I have an assignment (Spivak's Calculus) to show that the polar equation of a hyperbola with the right focus in the origin is ##r=\frac {±\Lambda} {1+εcos(\theta)}##, but the equation I reached was slightly yet somewhat disturbingly different, and I'm not sure...

Was there any need or utility or aim, for which Cantor created his theory? Did Cantor's theory clear any of the problems which existed before? (Though my user name is Cantor, I don't know lot about him or his theory :biggrin:) Reddit...

Now i had a question,but before that look at this. Now by the central dogma DNA is transcribed by RNA polymerase onto mRNA and this leads to translation which creates Protiens. But hold on...The polymerase itself is an enzyme ie ;a protein . So to make proteins...you need proteins aldredy...

Homework Statement A 2.4 kg particle-like object moves in a plane with velocity components vx = 25 m/s and vy = 80 m/s as it passes through the point with (x, y)coordinates of (3.0, −4.0) m. (Express your answers in vector form.) (a) What is its angular momentum relative to the origin at this...

Hello, Could someone help me find a general derivation of the formula for addition of capacitance of conductors? I'm hoping to find something that could be applied to a general assortment of conductors, not just parallel plate capacitors. I look forward to your response, Pete

If A is directly proportional to B, A ∝ B .If A is inversely proportional to B, A ∝ 1/B But where did the symbol ∝ came from?

Hey! :o Let $g:\mathbb{R}\rightarrow \mathbb{R}$ be arbitrary and $f:\mathbb{R}^2\rightarrow \mathbb{R}$ be defined by $f(x,y)=yg(x)$. I want to prove that $f$ is differentiable in the origin if and only if $g$ is continuous in $x=0$. So that $f$ is differentiable in $(0,0)$ does the...

If a gravitational wave passes an elastic body it will be deformed. The source of the work done on it comes from the energy of the gravitational wave. In curved spacetime e.g. an accelerated expanding FRW- or static Schwarzschild-spacetime an elastic body will be deformed too. What is the...

Homework Statement Express the electric field E due to a point charge q at the origin in cylindrical polar coordinates. Homework EquationsThe Attempt at a Solution Know that E = q / 4*pi*epsilon_0*r^2 in the r-direction, which is the answer in spherical coordinates. How we we swap to cylindrical?

1. A uniform linear charge density of 4.0 nC/m is distributed along the entire x axis. Consider a spherical (radius = 5.0 cm) surface centered on the origin. Determine the electric flux through this surface. Homework Equations L=2rπ φ=Q/ε λ=Q/L The Attempt at a Solution I found the charge by...

What's the latest about the origin of the moon? Is it true the moon is older than the earth? how?

I was wondering where does the 1/2 factor come from in the Euler-Lagrange equation, that is: L = \sqrt{g_{\mu \nu} \dot{x}^\mu \dot{x}^\nu} implies that \partial_\mu L = \pm \frac{1}{2} (\partial_\mu g_{\mu \nu} \dot{x}^\mu \dot{x}^\nu ) I'm not sure I entirely understand where it comes...

How come atom was proven to exist just because the electron was discovered in 1874, atom was like a fad of truth on early 1800s right, where atom was pictured at that time like a small brick of ball and nothing else (no electrons, neutrons, protons, parts, etc) and on that year also, chemistry...

I can't understand the exponential function fit for this set of data works well: ExpDec2 exponential function fit 0 3,04 10 2,77 20 2,52 30 2,27 40 2,09 50 1,92 60 1,75 70 1,62 80 1,51 90 1,43 100 1,36 110 1,29 120 1,24 130 1,19 140 1,14 150 1,09 160 1,05 170 1,02 180 0,99 190 0,97 200 0,95 210...

What is the origin of quantization? For example, electron of hydrogen atom has quantized energy level. But free particle has continuous energy level. Interaction with another particle or any potential acting on particle makes such quantization?

I have read in the internet that "One naturally derive the dirac equation when starting from the relativistic expression of kinetic energy: ##\mathbf H^2=c^2\mathbf P^2 +m^2c^4## where ##\mathbf P## is the canonical momentum. Inclusion of electric and magnetic potentials ##\phi## and ##A## by...

Homework Statement -infinity < r > +infinity Which of the following are equations for the line y=m*x for m<0: a. theta = -arctan(m) b. theta = arctan(m) c. theta = arctan(-m) d. theta = arctan(m) + pi e. theta = arctan(m) - pi f. r = 1/(sin(theta - arctan(m))) 2. The attempt at a solution...

Homework Statement and Homework Equations[/B] I was working on a math project involving certain simulations and a quarter circle. The equation of the quarter circle I used is y = r - SQRT(r^2 - x^2). Where r is the radius of a circle and x is greater than 0. The purpose of this is to model is...

I found this formula when I was studying neutron diffusion equation in Weston M. Stacey's book Thanks in advance cosβ=cosθx cosθ+sinθx sinθ cos(ψy−ψ) Edited by moderator for clarity: ##\cos(\beta) = \cos(\theta_x)\cos(\theta) + \sin(\theta_x)\sin(\theta)\cos(\psi y - \psi)##

I am involved in a discussion about the origin of religion. I made the statement that the very early humans who were speculating about the causes of things that frightened them and that they did not understand (wind, thunder, earthquakes) were engaged in philosophy and science. Their exercise...

I am having trouble understanding tangential speed as it applies to uniform circular motion and I would appreciate any help. Say I have a ball on the end of a string that I hold with my hand and rotate at a constant speed. If the string provides the centripetal force and acceleration, where...

Hi, I am new here. A while back I read articles about observations of supermassive black holes in the early age of the universe. What are the hypotheses that would explain how these black holes grew so large and so fast so soon? Could inflation play a role here? Like how inflation would be able...

At high school, we saw without demonstration the fundamental principle of dynamics (2th Newton's law), i.e : $$\sum \vec{F}=m \vec{a}\,\,\,\,\,\,\,\,\,eq(1)$$ after, at university, we saw another expression of this 2th Newton's law : $$\sum \vec{F}= \dfrac{d\vec{p}}{dt}\,\,\,\,\...

Science news reports: (original report abstract here) Eleven micro-fossils though to be the remains of bacteria (some dispute this) from Australia dated to 3.5 billion years ago have been analyzed with secondary ion mass spectrometry (SIMS). This has revealed different ratios of different...

Homework Statement Homework Equations First derivative=maxima/minima/vertical tangent/rising/falling When f'(x)>0 ? the function rises The Attempt at a Solution Deriving relative to x: $$10x-6(yy'+x)+10yy'=0~\rightarrow~y'=-\frac{x}{y}$$ What do i do with that?

Homework Statement Hello! I have 2 bodies initially at rest, of equal masses with the distance between them a and coordinates ##(a cos(\theta),a sin(\theta))## and ##(-a cos(\theta),-a sin(\theta))##. If we denote ##a_x## and ##a_y## the horizontal and vertical distance between them they...

Hi Forum I am trying to get a better grasp of the relation between electric field and the magnetic field. The overall question is "What is The origin of selfinductance in a current loop?" Here are my thourghts: A battery is connected to a say circular wire with some resistance. The current...

A stationary Monopole exist at the Origin. 1)##\vec{B} = \frac{g \hat r}{4 \pi r^2}## 2)##\vec{E} = \frac{e \hat r}{4 \pi \epsilon_0 r^2}## 3)## - \nabla \times \vec{E} = \frac{\partial \vec B}{c \partial t} + \frac{4 \pi}{c} \vec{J_m}## 4)##\nabla \times \vec{B} = \frac{\partial \vec E}{c...

nuclear

When two atoms undergo nuclear fusion, some of the mass is converted into energy, but where is this lost mass from? Atoms are composed of protons, neutrons, and electrons, but all three have all have set values for mass. What is the origin of this mass that is converted to energy?

hi, in perovskite crystal, such as BaTiO3, due to the off-centre of Ti ion, there exists a polarization moment in the unit cell (as shown in below link). my question is: does the disposition of Ti atom lead to separation of electron cloud from the nuclei of the Ti atom and so the Ti atom plays...