6
votes
3answers
274 views

Why doesn't visible light generate sparks in aluminum foil when microwaves do?

When aluminum foil is placed in a microwave, I see sparks generated by what I assume is dielectric breakdown. However, if I put aluminum foil in visible light (assuming the same intensity), there are ...
0
votes
1answer
94 views

Space and Time Equality and information transfer between particles existing at different time

Since space and time are the same is it that whatever happens at different positions in space should take place at different time? If what I think is correct consider an electric dipole, the charges ...
0
votes
1answer
155 views

About units and plural form

The plural form of physical units are always confusing me. I asked some senior students, some of them said we need to use plural form of units but some said units are always singular. For example, 1 ...
11
votes
3answers
967 views

There is no such thing as magnetism?

Here's an interesting "proof" that there is no such thing as magnetism. I know the answer but I love this so much I had to ask it here. It's a great way to confuse people! As we all know, $$\nabla ...
0
votes
1answer
90 views

Which physics subjects should a math major follow if s/he's interested in Smart Grid Networks?

I study mathematics and I would like to work on Smart Grid Networks in the (near) future. I would like to do so by applying optimization theory, percolation theory, Markov chains and more to problems ...
-3
votes
1answer
2k views

What causes electron to orbit the nucleus in an atom? [closed]

What causes the electron to orbit the nucleus? Which is the force that causes it to do so? Is it related to the Electro - Magnetic force? .
0
votes
1answer
43 views

Where can I find a device or how can I make a device that measures only Alpha particles?

Are there special muller tubes that only measure alpha for example?
5
votes
6answers
4k views

Where does gravity get its energy from?

I would like to know where gravity gets its energy to attract physical bodies? I know that the law of conservation states that total energy of an isolated system cannot change. So gravity has to be ...
1
vote
1answer
135 views

Does gravitational lensing violate Fermat's Principle that light must travel in straight lines?

Does bending of light due to warping of space violate Fermat's Principle or is it that in the principle light goes in a straight line with respect to space (taking space as the reference) and in ...
0
votes
2answers
440 views

Equilibrium of Force Systems including Torque

please help me to solve this problem.. this is only the #3 on my homework and the only thing i didn't know here is how to calculate the tension T. please teach me how to solve the tension here ...
3
votes
2answers
209 views

Physical intepretation of nodes in quantum mechanics

I am taking my second course in QM, and my head is starting to spin as it probably should. But I would very much like to clear up my head about a few details regarding the wave function. As I know it ...
0
votes
0answers
549 views

Statics: particle mechanics versus rigid body mechanics

In particle mechanics where the notion of rotation does not apply, particles are said to be in static equilibrium when the sum of the external forces acting on the particle of interest in all ...
0
votes
0answers
111 views

Problems at arriving on the fresnel drag coefficient $k=1-{1 \over n^2}$

I was studying about the Fizeau Water Experiment of 1851(I know the aether drag hypothesis has been replaced by Relativity, but I still wish to know the mathematical thinking about aether). So at one ...
5
votes
5answers
481 views

Does the reaction force appear without delay?

According to Newton's law of action-reaction, there is a reaction force for the action force. He did not say when the reaction appears, whether immediately or with a delay. Could you tell me the ...
1
vote
1answer
128 views

If the velocity of particle $A$ exceeds that of $B$, is the acceleration of $A$ greater than $B$?

Two particles $A, B$ are travelling along parallel straight paths. At some point, the velocity of $A$ exceeds that of $B$. Does this necessarily mean that the acceleration of $A$ is greater than the ...
2
votes
2answers
150 views

What is the experimental reason to believe in a Unified Theory?

Is there any experimental findings on behalf of the belief that all forces can be unified to a single force? Or the idea has it's inspiration from kind of thought experiment or philosophical belief.
2
votes
1answer
159 views

Why does a mirage disappear as you approach it?

Related: why do mirages only appear on hot day? The title says it all: why does a mirage disappear as you approach it? The related question does not answer this.
0
votes
2answers
240 views

Does heat radiation come from the nucleus or the electrons?

Is more of the thermal radiation due to acceleration of electrons or acceleration of the nuclei? Do electrons and nuclei carry the same fractions of thermal energy in a hot body?
3
votes
1answer
145 views

How does fire create thrust in rocket?

All big rockets are burning either gas or fluid to create thrust. While this is so, I have filled up a plastic bottle with air at high pressure, and it can go long distances by blowing the pressurised ...
2
votes
2answers
116 views

Can Deuterium undergo a nuclear fusion without the presence of Tritium?

I've been reading about fusion fuels for a while now, and I understand that in Lithium-Deuterium fuel, the neutrons from the fission reaction bombard the Lithium to produce Tritium and the D-T ...
-1
votes
2answers
76 views

orbitting around the earth

Does a space station need an initial velocity (tangentially) to be able to orbit around the earth or just the gravitational force acting downward on the station at certain height from the ground is ...
1
vote
1answer
99 views

How is momentum conserved when a magnet attracts a metal?

Suppose your have any magnetic object and no external force acts upon it, and the object comes near a metal which causes an impulse (think that will happen). However, the magnetic force is internal to ...
0
votes
1answer
117 views

What are magnetic field lines?

Does a magnetic field have concentrations of magnetic force lines as seen when putting iron filings over top a bar magnet or are these imaginary? I.e. are they just an artifact of the iron being a ...
3
votes
2answers
130 views

Can I excite an already unstable element for accelerated decay?

Say I had an unstable element ready to go through beta decay and I introduced it to high speed electrons: would this lessen the time needed for the product to go through beta decay?
5
votes
2answers
427 views

How to derive relation for time derivative in a rotating reference frame

I am looking for an appropriate derivation of the $(\frac{d}{dt})_{\text{laboratory}} = (\frac{d}{dt})_{\text{rotating}} + \omega \times $ relationship that enables one to calculate all desired ...
9
votes
2answers
267 views

Would this pump water up? and if so, how far?

I had this idea of an osmotic pump way back in high school and I never got a satisfactory answer if it would work. If I had this configuration: Would it continually pump water up given ambient ...
0
votes
2answers
413 views

Is it possible to deduce the conservation of angular momentum from the conservation of energy?

Is it possible to deduce the law of conservation of angular momentum from the law of conservation of energy? If possible, by what sense the conservation of angular momentum has the status of law, if ...
4
votes
3answers
260 views

Entropy and Information

Several posts and my classes in thermodynamics equate increase in entropy with loss of information. Shannon clearly showed that the information content of a message is zero when its entropy is zero ...
1
vote
1answer
167 views

Are multi-megaton antimatter induced fusion explosions theoretically possible?

I just finished reading this research about antimatter induced fusion and thermonuclear reactions. And one conclusion I could make is that very little mass of antimatter (in range of micrograms) is ...
-1
votes
1answer
473 views

Equation of progressive wave [closed]

A progressive wave traveling in positive x-direction given by $y=a\cos(kx-\omega t)$ meets a denser surface at $x=0,t=0$. The reflected wave is then given by: I know that since the wave changes its ...
-1
votes
1answer
95 views

Lunar and solar tides [closed]

I just read the following statement in a book: If the diameter of the earth increased by 20%, both lunar and solar tides would be weakened with lunar tides weakening more than solar tides. What ...
2
votes
0answers
64 views

State space of strings: Spin-1 particles in the conformal gauge?

I obviously have a problem with basics of group theory. consider an open string in flat spacetime. there are usually two common gauge to solve the classical problem and quantize the strings: ...
0
votes
2answers
281 views

General physics landau [duplicate]

I've found Landau 's book for a first course in physics (not theoretical physics, its title is general physics),the book is freely and legally avaible on archive.org ,but it's from 1967,is that ...
0
votes
1answer
88 views

Moon and Sun at the same time [closed]

Why do you see half of the moon when you can see both the sun and the moon from earth at the same time on some days?
1
vote
1answer
156 views

superposition of two states with different number of particles

In an electron gas with no mechanism of production or destruction of electrons is it possible to prepare an state which is superposition of states with different number of electrons? ...
3
votes
1answer
425 views

Evaluation of QED amplitude with 1 external photon

I'm trying to compute the exact QED amplitude with one external photon. Suppose that the photon has 4-momentum $q$ and polarization $\varepsilon^\mu$. Peskin and Schroeder (p318) claim that ignoring ...
-1
votes
1answer
202 views

Can parallel universes constitute the missing mass aka dark matter?

I was pondering about this question for a while now. And with my limited knowledge of physics I can answer myself - if parallel universe theory is true and if indeed there is gravitation leakage from ...
0
votes
1answer
566 views

Calculate Magnetic Flux Density between Two Disc Magnets

If I have two disc-shaped magnets (radius r=0.05m, width w=0.03m, Remanance Br=1.06 T) separated by a distance d, how can I calculate the magnetic flux density somewhere between them? I found this ...
6
votes
2answers
176 views

Physical consequences of non-abelian non-trivial holonomy

The Aharonov-Bohm effect (http://en.wikipedia.org/wiki/Aharonov%E2%80%93Bohm_effect#Significance) can be well described and explained in terms of holonomy of the $U(1)$ connection of the ...
0
votes
0answers
50 views

Can we make any substance that will produce ions at low temprature

I am talking about thermal ionization, Is to possible to make any material or is there any element that can be ionized at let say 20 degree centigrade Temperature? I am a computer engineer and into ...
3
votes
0answers
161 views

Is it possible to have a magnet which looks like a hollow cylinder and who's north is interior and south is exterior? [duplicate]

Is it possible to have a magnet which looks like a hollow cylinder and who's north is interior and south is exterior? What then happens as the cylinder gets longer? Would that affect the strength of ...
10
votes
1answer
424 views

Motivation for preservation of spacetime volume by Lorentz transformation?

My favorite way of deriving the Lorentz transformation is to start from symmetry principles (an approach originated in Ignatowsky 1911; cf. Pal 2003), and one of my steps is to prove a lemma stating ...
1
vote
1answer
73 views

Can radioactive isotopes stay unstable after beta decay?

Say you had a very radioactive element in a confined area: could that element (hypothetically speaking) go through beta decay, then, once it has too many protons could it immediately go through ...
7
votes
2answers
229 views

Fermions in the same state

I need some clarification of what is meant when someone says "fermions cannot occupy the same quantum state". Consider two bosons: $$\psi(\vec{r_1}, s_1, \vec{r_2}, s_2) = \frac{1}{\sqrt{2}} \left( ...
1
vote
2answers
315 views

Boundary between supercritical fluid and gaseous phase

As far as I understand, going around the critical point, it is possible to transform a liquid into a gas without seeing a phase transition. Does this also mean that there is no clear separation ...
2
votes
0answers
124 views

Generalisations of AdS/CFT with string theory on both sides

From my previous post, I found out from the comments that there are various generalisations of AdS/CFT with different things replacing the CFT on the RHS; such as AdS/CMT, AdS/QCD, and also with ...
2
votes
1answer
363 views

Why are magnetic fields only produced by moving charges? [duplicate]

Why do charged particles only produce magnetic fields while in motion?
2
votes
1answer
63 views

Is the “pressure” as we know a kind of “instantaneous action at a distance”?

This may be a very simple question, but I still dont know how that work in the essence (quantic/atomic level) Consider the image bellow: How the "pressure (air atoms) " known that in the other ...
0
votes
0answers
82 views

Practical examples or demonstrations similar to the Chaplygin sleigh

The Chaplygin sleigh is a simple nonholonomic mechanical system. The WP article is a fresh one that I just wrote based on a description by Bloch, and may contain mistakes. The first thing I thought ...
-3
votes
2answers
88 views

A simple question [closed]

This is a simple question but it seems to me that both the explanations are acceptable. Let say the least distance of least distinguished vision is 25 cm. An object is placed 12.5 cm in front of a ...

15 30 50 per page