Why do photons interact with e- but not with other photons?]]>

The very talented 21 year old Norwegian singer and songwriter Sigrid:

...

Favorite songs (new thread)]]>

One of the questions that I have is what percentage of white Americans are descended from those Europeans...

Question: what % of white Americans have colonial roots?]]>

“... vacuum fluctuations cause a particle–antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole while the other escapes. In order to preserve total energy, the particle that fell into the...

Hawking Radiation and the Negative Energy Particle]]>

What, in essence, distinguishes light from matter?]]>

The frequency of a tsunami large enough to threaten the safety of a nuclear power plant has been estimated to be 1 in 200 years. If the plant’s life is 65 years what is the probability it will be damaged by such a tsunami? What...

Nuclear Probability Question]]>

When I'm not purposefully trying to do something with the mouse, I often keep my hand on it without paying attention to what its doing with...

"Mute" pointer to avoid pop-ups]]>

. View attachment 225995]]>

The problem is simply...

Cannot find the Temperature Change inside of a Tank]]>

This isn't really a homework, but I am trying to figure out how this would work.

I have an plano-convex lens with an focal length of 500 mm. I have an laser source that I like to focus on, to the infinity. I.e. I like to see...

Image with an Plano-Convex lens]]>

The CMF armor on collision literally converts the projectile into small particles, spraying out.

This is interesting and definitely not my area.

Watch the attached video.

Questions:

1. the particles resulting from the...

CMF bulletproof body armor]]>

Okay, let's...

How do helmets help prevent injury to the head?]]>

First of all, I am new to this thing and I hope you guys can help me with this.

So I am Ruzanna, a freshman,(I am 14 years old) and live in the Netherlands.

So, I have this project for physics where I had to make my own pendulum, and use it to calculate the gravity here.

Well I...

Calculating gravity]]>

The two sinusoids...

Phase modulation and intermodulation anomaly *Plots inside*]]>

*Copyright http://www.feynmanlectures.caltech.edu/III_01.html

But the curve for ##P_{12}## looks in the picture is different from his live...

Feynman experiment with bullets]]>

Like church made geocentric theory but copernicus made heliocentric using observations.

Did he have to learn geocentric first?

I am asking this because if the people are studying...

How are new theories developed?]]>

I was watching a documentary by Professor Brian Cox and he said human life is only possible for 10

When will the Universe end?]]>

Relationship of Young's modulus and impulse force]]>

We have a rod with length L and with the left end the rod is fixed to the ceiling in such a way it can swivel. As we can see from the picture (attached file) on right end two forces are acting on the rod: F and mg.

The question...

How does the incline of the rod depend on mass and force F?]]>

Calculate the induced EMF in a conductor loop when the angle between [tex] \vec{A} ~ and~ \vec{B} ~is~ changed ~from ~{0 °}~ to ~{α °} [/tex]...

Calculate the induced EMF for angle α]]>

The capillary number is defined as ##Ca = \mu V/\sigma##. Does more inertia in a fluid increase the capillary number?

As inertia increases, it's my intuition that so does velocity. Then it seems (all else constant) that ##Ca## increases too. Is this correct?]]>

*Motorcycle stator off an old Yam RD350 (known as RZ350 in the US) needs rewinding after some of the coils were "fried".

*The stator has 3 larger high voltage coils used for the CDI system - and is left...

Rewinding old 3-phase stator: Non-symmetrical layout]]>

In the attached file we can see simplified ladder. I am interested on which side (right or left) the forces are correctly drawn.

I would draw forces as the right side...

Forces On Top Of The Ladder]]>

This creates a problem for high school...

There are no particles, only fields!]]>

A crane is moving two equally spaced masses to the roof. One box is 10kg and the other box is 20kg. As the plank tilts towards the 20kg box, at what angle will each box begin to slide? The coefficient of static friction is 0.4...

Determining the angle for a mass to overcome friction]]>

So the scenario is this, lets say an object such as a huge star or galaxy was to just...

Perceived Speed of Objects in Space]]>

Intro to Algorithms for Programming

View attachment 225957

...

Intro to Algorithms for Programming - Comments]]>

So I just finished a course on Qm with Griffiths but the teacher was not the best, to say the least. I disliked the book too and its kind of childish or funny way of presenting stuff.

During the summer break I want to go over QM again but with a better book and by myself. I loved...

Self-studying QM after course]]>

Global Carbon Content of Groups of Organisms]]>

Here is what I know:

a) The angle relative to the right focus with 0 radians being the...

How to get tangential velocity]]>

For instance, if a hypothetical alien lived in MACS0647-JD galaxy which is 13.3 billion light years away,...

Doesn't there have to be more than one observable universe?]]>

View attachment 226054

I don't understand what he's getting at in the sentence I...

Hamiltonian integral transformation]]>

I have calculated the molar absorptivity of phenol, I'm pretty sure it's correct but I can't for the life of me figure out what I've done. Any help would be really appreciated.

Beers Law:

A = εbc...

Calculating the molar absorptivity]]>

I have the wave function Ae^(ikx)*cos(pix/L) defined at -L/2 <= x <= L/2. and 0 for all other x.

The question is:

A proton is in a time-independent one-dimensional potential well.What is the probability that the proton is...

Normalization of wave function]]>

Somebody may advise me to add few videos and save them before moving on to the next set. That...

Saving a temporary draft while adding media]]>

How to approach this photoelectric effect question]]>

I am aware there are probabilistic and deterministic models available for QM. Does that mean QM could be...

Probabilism and determinism]]>

Transformer Phasor Diagrams]]>

Updated about an hour ago

Fri 4 May 2018, 7:44pm

http://www.abc.net.au/news/2018-05-04/volcano-in-residential-area-in-hawaii/9728316

video on that page

lots of other links .......

Hawaii's Kilauea volcano eruption]]>

I am asking in reference to this paper:

https://arxiv.org/pdf/1604.07422.pdf

Which claims to show...

Does the Frauchiger-Renner Theorem prove only MWI is correct]]>

I have the following product, and I am looking for a summation equivalent

[tex]\prod_{k=1}^K\left(1-\frac{1}{x_k+1}\right)[/tex]

Is this doable? I tried to use partial fraction but got nowhere!!

Thanks in advance]]>

I was wondering if this (Image) can work. (Is something like this possible?)

View attachment 226035

The idea is that if we have logic 1, AND gate gives 1 while NOR gives 0. And vice versa.]]>

We are currently learning about nuclear stability in class by looking at the nuclear stability graph when you plot the proton number against the neutron number. I understand that if an isotope is on the stability line then it is not radioactive. Therefore unstable nuclei have too many...

Why is Carbon-14 Unstable?]]>

Which of the following sets are subspaces of

##W_1 = {f \in \mathbf R[x] : f(0) = 0}##

##W_2 = {f \in \mathbf R[x] : 2f(0) = f(1)}##

##W_3 = {f \in \mathbf R[x] : f(t) = f(1-t) \forall t \in \mathbf R}##...

[Linear Alg] Determining which sets are subspaces of R[x]]]>

<speculative link deleted>

I have now become interested in what gravity does to light. My understanding of the post above is that the reference frame for light...

Does gravity impact the speed of light?]]>

From undergraduate physics (a few years ago for me) I roughly remember how to derive reflection and transmission coefficients for a wave travelling from one medium to another with a...

Effect of impedance changes less than a wavelength]]>

Earth's twin planet]]>

Consider this infinite descending sequence of submodules of ##M##

##M \supseteq f(M) \supseteq f^2(M) \supseteq f^3(M) \supseteq \cdots (1)##

Can anybody show that the sequence (1) is strictly descending if ##f## is injective...

A decreasing sequence of images of an endomorphisme]]>

Thanks]]>

If you have kids/will have kids, what would you want them to know by the time they enter the work force?]]>

Path integrals (and generalizations) are sums over configurations. A logical extension of that process would be to sum not over configurations, but over theories (configurations are possible solutions of a single theory).

Renormalization already plays around...

Summing not over configurations, but over theories]]>

Please start off with "Today I learned". Keep commentary to a minimum and just LIKE posts. I'll start!

Today I learned that you clean...

Today I learned]]>

My interests involve, robotics, artificial general intelligence, 3D graphics, computer vision, neural nets, file compression and aerospace engineering(It’s an...

Best complementary degree for computer science?]]>

View attachment 226036

I managed to find dy/dx as follows:

View attachment 226037

But I'm having difficulty finding the second derivative. I've...

2nd order differential equations]]>

I am studying Gerry's <Introductory Quantum Optics>, in which there is an integral (Eq. 4.37)

$$\intop_{-infinity}^{+infinity}\frac{[sin(\triangle t/2)]^{2}}{\triangle^{2}}d\triangle=\frac{\pi}{2}t.$$

I don't know how to get the...

How to get the integral result?]]>

Similarly if a battery is connected to a pn junction diode such that positive terminal is connected to negative...

Pn junction under forward bias]]>

I was wondering if there is anybody who completed this program or is still doing it now.

I wanted to know what is its level of difficulty and how is the educational environment.

Please tell me your experiences I...

Mathematics and Physics (undergrad) at University of Toronto]]>

John and Eli are playing a game with a hall that can roll into one of two

pockets labelled H and Y. John wants to keep the hall in H and Eli wants

to keep it in Y. When it is John's...

Build a Markov Matrix]]>

Relativity and speed of light basics]]>

Is it that chrome got to know about it and has defeated it?

But why is the virus still...

Google chrome virus]]>

Gisin, N. (2011). Impossibility of covariant deterministic nonlocal hidden-variable extensions of quantum theory.

proving that, under sensible hypotheses,...

Relativistic hidden variable quantum mechanics?]]>

I'd appreciate it if anybody can point me to an evidence.]]>

I have a question regarding Maxwell's Equations and Faraday's unipolar induction equation.

If we study the case of a cylindrical magnet with a radius of r which is rotating about its axis

with angular velocity w. The electrons within the magnet collide with the moving atoms, causing...

Faraday's Unipolar Induction Equation]]>

I'm asking this because I'm studying how it's derived and I don't have any Relativity book in hand so that I can look up its application...

Example of the use of the Lie Derivative in Relativity]]>

:3 Wish you guys a terrific day!]]>

Since magnetism and electricity are related, and magnetic field inside a magnet is from South to North (outside it is North to South), i doubted for any correspondence.]]>

So there are very little Information Technology jobs around in my area according to indeed.com. I'm currently contributing to open source on GitHub (which is legally a job, but it's not a paid job). I'm really trying to get back into my field of computer science/information technology,...

Need help getting back into a helpdesk position]]>

Derivation of the energy principle from Gregory Classical Mech]]>

I was searching for a secondary source on investigating the effect of temperature on membrane permeability of beetroot and i need the d.v. values in transmission%.

But Im getting the dv values in Hunter (‘L’ (lightness), ‘a’...

Problem with conversion]]>

Hello at all!

I have to calculate total energy for a nucleons system by equation:

##E_{tot}=\frac{1}{2}\sum_j(t_{jj}+\epsilon_j)##

with ##\epsilon_j## eigenvalues and:

##t_{jj}=\int...

Laplacian in spherical coordinates]]>

I have found two reasons for this:

1. Scanner class manages exceptions implicitly, while for BufferedReader, exceptions have to be handled either by...

Preferring Scanner to BufferedReader for taking input]]>

Have to read a paper and somewhere along the line it claims that for any distinct ## \ket{\phi_{0}}## and ##\ket{\phi_{1}}## we can choose a basis s.t. ## \ket{\phi_{0}}= \cos\frac{\theta}{2}\ket{0} +...

2D subspace of a Hilbert space]]>

Is it possible to make graphs using C++?]]>

I just want to confirm that, ofc there is no affine parameter for a null geodesic and so you...

Coordinate and proper time, null geodesic]]>

So, I found out that the images taken by the Hubble Space Telescope are not colored but black and white and colors are added to them later. I thought that the way you figure out what colors are present in your...

How is color added to Hubble images?]]>

Teaching Economics Without Calculus]]>

Do macro objects get entangled?]]>

Is it possible to perform accelerated lifetime test of thermal ageing on power cables?

Let's assume that the cable manufacturer guarantees a service life time of 20 years at max operation temperature 90 [degC]. Is it possible to estimate the expected life time of a cable if I choose to...

Accelerated lifetime / thermal ageing of power cables]]>

Turns out that Zoobyshoe beat me in posting about this in another thread, so he will officially be known...

Weird News Compilation]]>

α =Δω/Δt = 0

But static torque still has centripetal acceleration with constant speed:

a

where v is linear velocity, and r is...

How is static torque calculated for constant speed?]]>

In most of the theory I have seen so far, the latter is more convenient to use. Why is...

Definition of a neighborhood]]>

Polarity of magnetic field in a conducting wire]]>

consider a (finite dimensional) vector space ##V=U\oplus W##, where the subspaces ##U## and ##V## are not necessarily orthogonal, equipped with a bilinear product ##*:V\times V \rightarrow V##.

The subspace ##U## is closed under multiplication ##*##, thus ##U## is a

Subalgebras and direct sums]]>

Intuition tells me the working end of the tube should be kept in the...

Minimum length of the Pitot tube?]]>

I am encountering some confusion understanding the difference in working with reversible and irreversible processes in thermodynamics. Lets say I have a process where an ideal gas at a certain starting temperature ##T_i## expands from volume ##V_i## to ##V_f##. The temperature of the...

Work done in reversible and irreversible processes]]>

A rod is attached to a wall in such a way it can swivel. In this case: In which direction does the force (of the wall on the rod) point to?

Here are two examples (see under attached files), but the the direction of the force is...

Direction of The Force of a Wall Exerted on a Rod]]>

I am currently doing research on the aerodynamic properties of a rotating cylinder in a cylindrical housing.

The cylinder represents a rotor in a electric motor. The air gap between rotor and stator is about 0.5mm.

I'm looking for a theoretical analysis and calculation on the...

Air resistance: cylindrical rotor in stator with air gap]]>