7
votes
2answers
231 views

How to find 'good' literature on a phenomenon?

With this being a potentially subjective question I know I'm threading on thin ice, but this is an actual "physics" problem I face from time to time: The situation is this: I hear about some ...
4
votes
2answers
641 views

Predicting Decay Rates via the Standard Model

Question 7584 illustrated a procedure to forecast the decay rates of isotopes with known long average lifetimes. Lifetimes of the many U isotopes vary from micoseconds to gigayears. F has only one ...
-2
votes
1answer
1k views

How to validate a new physics theory and keep the credit for it [closed]

For the last few years, My friend worked on figuring out the "theory of everything". She is afraid of sharing her theory with well known physicists, because she doesn't want other people to take ...
14
votes
4answers
3k views

Energy conservation and interference

I have a problem with energy conservation in case of interfering waves. Imagine two harmonic waves with amplitudes $A$. They both carry energy that is proportional to $A^2$, so the total energy is ...
0
votes
1answer
406 views

Does quantum mechanics prohibit extraterrestrial life? [closed]

There is a known thought experiment, connected to quantum immortality: a duel between physicist and a philosopher. Each turn physicist and philosopher fire at each other with a pistol. The quantum ...
7
votes
3answers
2k views

Definitions and usage of Covariant, Form-invariant, Invariant?

Just wondering about the definitions and usage of these three terms. To my understanding so far, "covariant" and "form-invariant" are used when referring to physical laws, and these words are ...
5
votes
1answer
209 views

Is it true that the angular momentum of electromagnetic waves in an anisotropic medium is an integral of motion?

Extending my previous question Angular moment and EM wave, does it make sense to talk about the angular momentum of electromagnetic waves in an anisotropic medium? It is not obvious that the angular ...
3
votes
1answer
489 views

Nature of tetragonal distortion in Jahn-Teller effect

I am wondering: If I have a regular octahedron as my starting point, oriented along the x-y-z axis, and now Jahn-Teller suggest I elongate or compress along the $z$-axis, what happens along the other ...
2
votes
1answer
549 views

Internal Energy and entropy in a open system

Here http://en.wikipedia.org/wiki/Internal_energy we can read $$U= TS-PV+\sum_i \mu_i N_i$$ Let's suppose i=1 and a ideal gas. We know: $$U=N/N_A c_v T$$; $$PV=NKT$$; $$\mu=\frac{\partial ...
1
vote
1answer
411 views

Extracting water out of silica gel [closed]

From my preliminary research I've learned that desiccants are a good (best?) method to absorb water from air. Assuming I'm using silica gel (or kitchen salt, or rice) then what is the best way to ...
4
votes
2answers
2k views

“Artificial gravity” on a rotating space stations

There have been a lot of sci-fi shows recently using the "rotating space station" explanation for gravity on space stations. After watching these videos: ...
12
votes
3answers
3k views

Perturbation theory with degeneracy even after 1st order

Most textbooks on basic quantum mechanics tell you that when your initial Hamiltonian $H_0$ has degenerate states, then before you can do (time independent) perturbation theory with a perturbation ...
7
votes
1answer
365 views

How to simulate a crashing wave? [closed]

I'd like to create a very rough animation of a wave crashing on a beach. I'm guessing it would have to be a particle simulator, where you code in the forces between the particles and then integrate ...
3
votes
1answer
639 views

live Kp index data

I need to create an online service displaying latest Kp index. Where I can take the data? The data should be in machine-readable format, i.e. text files, XML, or CGI gateways, for instance. No ...
7
votes
1answer
693 views

In Method of images type problems, why isn't the induced charge taken into account while solving it via Green's functions?

To take the simplest example, $$\Phi(\vec{r}) = \begin{cases} V & r\leq a \\ 0 & r\geq a \end{cases}$$ For a plane conducting surface that extends all the way. Choosing an appropriate ...
24
votes
4answers
3k views

Fundamental question about dimensional analysis

Let me admit beforehand that this is quite possibly a very stupid question. I was also uncertain of where to post this question, as it doesn't fit cleanly into either physics or math stackexchange. ...
2
votes
2answers
1k views

Electric field at a point from a square surface

I'm trying to determine the electric field at a point P (located on the +Z axis) due to a square of side length [L] and centered at the x-y plane origin. The square has a constant surface density [s]. ...
8
votes
3answers
2k views

Does a particle annihilate only with its antiparticle? If yes, why?

Or to put the question another way - what is the result of a proton-positron collision, or an up quark-charm antiquark collision, etc.? As far as I know, annihilation happens only between particles of ...
8
votes
4answers
3k views

Static Friction - Only thing that can accelerate a train?

I'm a computer programmer that never studied physics in school and now it's coming back to bite me a bit in some of the stuff I'm being asked to program. I'm trying to self study some physics and ...
13
votes
2answers
561 views

Brachistochrone problem in general relativity

This question Brachistochrone Problem for Inhomogeneous Potential has the obvious extension. Namely the same question, when gravity is treated according to general relativity. To make it specific ...
9
votes
8answers
2k views

What future technologies does particle physics and string theory promise? [closed]

What practical application can we expect from particle physics a century or two from now? What use can we make of quark-gluon plasmas or strange quarks? How can we harness W- and Z-bosons or the Higgs ...
1
vote
1answer
411 views

Mass fixed to a wheel - mechanics problem [closed]

I am struggling with a problem from classical mechanics. Imagine a massless wheel (to make it simpler) with a mass $m$ fixed to it rolling without slipping on a horizontal ground. If we now try to ...
2
votes
2answers
570 views

Iodine isotope question

Quick question for the nuclear engineers/physicists out there Where does I-134 come from? I cant find it in any of the charts of standard decay products of Uranium fission, but there is tons of the ...
1
vote
2answers
374 views

Finding $\psi(x)$ from Fourier modes [closed]

In quantum physics we've defined: $$ \psi (x) = \sqrt{ \dfrac{1}{2 \pi \hbar} } \int^{ \infty }_{-\infty } \phi (p) \exp \left( i \dfrac{px}{ \hbar} \right) dp $$ Now, $$a(k) \equiv \sqrt{ \hbar } ...
0
votes
1answer
822 views

Proving Operator identities (Quantum Physics)

How would I go about showing: $$\hat{A}^{\dagger} + \hat{B}^{\dagger} = \left( \hat{A} + \hat{B} \right) ^{\dagger}$$
2
votes
4answers
3k views

What could make the SWITL materials behave like this?

SWITL - what could this be? Ultra thin paper with some adhesive that binds to fat? (or as I originally thought, a hoax)? A robotic hand to scoop gel-like substances... ...
0
votes
3answers
2k views

Direction of Magnetic force from a current running through a coil of wire

What is the direction is the magnetic force vectors pointing from a coil of wire that has current running through it? ...
1
vote
1answer
467 views

Does change of coordinate system require acceleration?

This question came about from a side discussion that arose on this: Does GR provide a maximum electric field limit? Can we change our choice of coordinate system completely independent of physical ...
3
votes
1answer
1k views

Chemical potential interpretation

Something that has bothered me for a while regards the interpretation of chemical potential for different statistics. While I understand its meaning in metals (and its relation with the Fermi ...
4
votes
1answer
449 views

Katz and Vafa's work on F-theory

I would like to know about the larger picture, current state and future prospects of the sequence of papers that were written by Sheldon Katz and Cumrun Vafa on F-theory. (Freddy Cachazo was also a ...
7
votes
2answers
977 views

How do I develop an intuitive model of spacetime?

I am your nightmare poster - a layman trying to learn special relativity. (I'm also a refugee from stackoverflow.com: trust me, it's only going to get worse). Apologies in advance if my question is ...
9
votes
3answers
2k views

What is the difference between a neutron and hydrogen?

Differences? They are both an electron and a proton, since the neutron decays to a proton and an electron, what's the difference between a neutron and proton + electron? so is it just a higher binding ...
8
votes
2answers
26k views

What is in the space between a nucleus of an atom and its electrons?

There is a common analogy about the structure of an atom, such as the nucleus is a fly in the centre of a sports stadium and the electrons are tiny tiny gnats circling the stadium (tip of the hat to ...
1
vote
3answers
557 views

Where can I find pirated copies of journals? [closed]

As you all know, journal subscriptions are extremely expensive, and many colleges and libraries don't subscribe to them. Many important articles aren't available on the preprint server arxiv. My ...
6
votes
6answers
1k views

List of physics paradoxes [closed]

What are some important examples of paradoxes in physics which are still currently unresolved?
4
votes
3answers
497 views

Particle Lagrangians

As I learned in my string theory course, you can describe the quantum spin-0 particle by quantizing the arclength Lagrangian of a relativistic classical particle. My question is whether you can get a ...
13
votes
2answers
4k views

How do we know that some radioactive materials have a half life of millions or even billions of years?

If a radioactive material takes a very long time to decay, how is its half life measured or calculated? Do we have to actually observe the radioactive material for a very long time to extrapolate its ...
2
votes
2answers
269 views

Representation of quantum transformations as matrices

I was reading Quantum Computation explained to my mother, which makes the following claim Postulate 2 A closed physical system in state V will evolve into a new state W , after a certain ...
1
vote
4answers
1k views

Will Earth Hour do damage to power supply system?

There is always a debate around Earth Hour every year, and the opposite side of Earth Hour usually claims that The (sudden) decrease and increase of the power usage in the start and end of Earth ...
4
votes
2answers
296 views

What does this observation of instantaneous velocity in Brownian particles mean?

I read this artice: Physicists Prove Einstein Wrong with Observation of Instantaneous Velocity in Brownian Particles “We’ve now observed the instantaneous velocity of a Brownian particle,” says ...
1
vote
1answer
762 views

Can reading glasses improve one's eyesight of objects lying in the long range?

Someone told me that reading glasses (a priori with a magnifying glass effect only) improve one's eyesight of objects lying in the long range distance. I am really sceptic about it since everything is ...
7
votes
3answers
476 views

Horizon and Unruh radiation for a finite period of acceleration

It's a well known fact that an observer that accelerates at a constant rate from $-c$ at past infinity to $+c$ at future infinity sees a horizon in flat Minkowski spacetime. This is easy to see from a ...
2
votes
1answer
1k views

Fermi-Energy Level for Extrinsic Semiconductor

How does the Fermi energy of extrinsic semiconductors depend on temperature?
3
votes
1answer
269 views

determination of voltaic cell voltage

if i understood this correctly, the determination of voltage for a specific voltaic (gallvanic) cell is determined only by the chemical correlation between the two metals. is this true? for an ...
7
votes
1answer
676 views

Question about a Limit of Gaussian Integrals and how it relates to Path Integration (if at all)?

I have come across a limit of Gaussian integrals in the literature and am wondering if this is a well known result. The background for this problem comes from the composition of Brownian motion and ...
8
votes
5answers
672 views

How would I go about detecting monopoles?

A question needed for a "solid" sci-fi author: How to detect a strong magnetic monopole? (yes, I know no such thing is to be found on Earth). Think of basic construction details, principles of ...
5
votes
6answers
928 views

Is there any inherent danger in operating a Thermonuclear Reactor?

Nuclear fusion research appears to promise sustainable, practically unlimited energy, and according to ITER it will be a perfectly safe, non-polluting source of energy. My question is if there are ...
6
votes
1answer
482 views

What is the purpose of a “protect from light” warning?

Some food or medical items, like rasberry juice concentrate I just bought, have a "protect from light" warning on the label. How can light influence products like milk and what does this warning mean ...
6
votes
4answers
536 views

Going Beyond Introductory Physics [closed]

Due to certain reasons, I don't have the chance for going to college for under-graduation, but that doesn't mean I can't choose to walk the hard path and learn. Over the past month or so a lot of ...
1
vote
2answers
410 views

Gravity and the Standard Model

Gravity is ignored in the SM. The proton rest mass is ~0.938 GeV/$c^2$. LHC protons will move with 7 TeV energy, presumably with a relativistic mass about 7,450 times rest mass. A cosmic ray with the ...

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