All Questions

209 views

Fracture because of high-speed rotation

I was watching a rerun of an early MythBusters episode, where they look at whether CDs in high-speed drives can explode / fail simply because of being rotated too fast. The following are some ...
544 views

Electron model under Maxwell's theory

I was not able to recall my memories, so: What is the formula that states the frequency of electrons revolving around nucleus is equal to the frequency of light (or photon) emitted (or radiated)? (I ...
737 views

Does $p=mc$ hold for photons?

Known that $E=hf$, $p=hf/c=h/\lambda$, then if $p=mc$, where $m$ is the (relativistic) mass, then $E=mc^2$ follows directly as an algebraic fact. Is this the case?
220 views

Can a large thermonuclear bomb be used for planetary defence?

How effective would a thermonuclear device of 47 megatons or higher like the zsar bomba be in space? Could we use as planetary defence on somthing like an asteroid as long as it is detected in time ...
258 views

Pressures Necessary for Carbon Detonation

Carbon detonation is a characteristic event of Type 1a Supernova (EDIT: where an accreting white dwarf near the Chandrashankar limit of 1.4 solar masses explodes), an extremely important standard ...
394 views

What is the single particle Hilbert space?

I know what an Hilbert Space is, but I'm not sure what exactly is the single particle hilbert space; I understand it as the space of all possible states of the particle; does it matter if you're ...
253 views

Exchange operator in terms of rotation operator

I have studied about exchange operators and rotation operators and I know that an exchange between 2 particles in a combined state is the same as rotating each particle 180 degrees (according to ...
353 views

What happens if an object has more kinetic energy than the Gravitational Binding Energy?

So the binding energy of an object is the amount of energy needed to move it an infinite distance away from another mass to essentially “escape” its gravitational field. But what happens if you give ...
478 views

My physics knowledge is (sadly) very infinitesimal and I have a question about a calculation which I think is wrong, but want to be sure. I tried to calculate the potential of a finite line charge. ...
227 views

What's the most efficient strategy to shake a bottle to create a global flow?

Consider a bottle of orange juice with pieces of the fruit gathered at the bottom of the bottle. You need to shake the bottle to evenly distribute the pieces in the bottle. The first part of the ...
131 views

Does cosmic expansion imply the possibility of the universe splitting in half; multiple big-crunches?

There is an event horizon where cosmic expansion leads to superluminal recession speeds for sufficiently distant objects -- the Hubble Volume. 1) Does matter beyond the event horizon affect us ...
294 views

Quantum experiments in the pre-industrial era

Could an 18th century or earlier scientist have come across phenomena which require quantum theories to explain them, given the apparatus available at the time? I'll choose 1805 as the cut-off date, ...
5k views

How does the Higgs Boson gain mass itself?

If the Higgs field gives mass to particles, and the Higgs boson itself has mass, does this mean there is some kind of self-interaction? Also, does the Higgs Boson have zero rest mass and so move at ...
174 views

What would be the requirement to learn matrix mechanics? [duplicate]

What would be the requirement to learn matrix mechanics? More specifically, what math do I need? Can anyone recommend me a book that covers all maths needed for matrix mechanics?
464 views

failing to see the conundrum in the Einstein hole argument

I've been reading about the Einstein hole argument, and i fail to understand what makes active diffeomorphisms "special" compared to passive diffeomorphismsm also known as good old coordinate ...
418 views

Compton scattering multiple wavelengths?

The formula given for compton scattering shows that when x-ray of one specific wavelength hits carbon or some materials, emitted x-ray will be of one new specific wavelength. However, according to ...
1k views

NED velocity to redshift conversion?

I've done some search with the Nasa Extragalactic Database (NED) and I have a very basic question about the velocity/redshift conversion. For example, for the first object of this page, we have ...
207 views

Mathematical problems with impact on physics [closed]

Are there any purely mathematical, unsolved questions, whose resolution would have (great, or concrete) impact on physics? Eg. it could almost surely tell us whether particle x exist or not, assuming ...
1k views

What is the best material and design for building a parabolic dish? [closed]

I'm currently using a homemade metallic spaghetti strainer with a wifi adapter inside it to increase my wifi adapter's signal reception, but would think that a different material, like the aluminum ...
491 views

EMF in a half-ring shaped conductor around a solenoid

A half-ring shaped conductor is being placed around a solenoid. This solenoid has a changing magnetic field. a) There is a current and EMF (Electromagnetic force) in the half-ring shaped conductor b) ...
349 views

Causality in String Theory

For a point particle we have light cone: String Theory- with it's extended body concepts- however will not admit a light cone such as this. In particular the most problematic causal issue would be ...
1k views

Find wavelength from relative permittivity and frequency

If i have a EM wave with frequency 1MHZ and εr=9 in a perfect dielectric ,is it possible to find the wavelength λ and wave propagation speed ? It seems impossible to me..
437 views

What is the typical orbital life of an artificial satellite?

The orbit of satellites around Earth eventually decays, or so I read. This is typically caused either by atmospheric drag, or by tides. I would assume most satellites have a limited service life in ...
295 views

Determining axis of rotation from angular speeds about axes

I think my pure-math head is messing with me on the question below: my physics and CS friends both seemed to think it was a simple computational thing, and my program says the method works, but now ...
681 views

Light bulbs with voltage source or current source

When we connect 2 light bulbs to a voltage source in parallel, the equivalent Resistance of the bulbs is R/2 (1/Req = 1/R + 1/R). If we connect these lights in parallel we have Req = 2R; I= V/Req is ...
603 views

Bosonic Tachyon Condensation?

The tachyonic string mode in perturbative bosonic string theory indicates that the "vacuum", flat Minkowski $\mathbb{R}^{25,1}$, is not really a vacuum. What is conjectured about tachyon condensation ...
592 views

What's the optimal shape for a continuous Galilean Cannon?

A Galilean Cannon is a toy similar to the famous basketball-and-tennis-ball demonstration. You take a tennis ball, balance it on top a basketball, and drop them both. The tennis ball will bounce up to ...
142 views

Maximum precision of deterministic measurements

Okay, I tend to have some weird thoughts, so bear with my odd question here. Suppose you have a collection of particles that obey Newtonian mechanics. For simplification, all particles are identical ...
414 views

Hierarchy is no problem and susy is a mathematical tool for data fitting

I saw this paper in the arXiv: http://arxiv.org/abs/1206.4711. The author seems well-known and has many very well cited papers. But what he says sounds very strange. What I get from this paper are ...
686 views

Why didn't Newton just propose the 2nd Law and leave it at that?

Why didn't Newton just propose the 2nd Law ($F=\dot{p}$) and leave it at that? The 2nd Law implicitly contains the first, doesn't it? If so, it seems he wasn't following his own Rule #1 of Book 3 of ...
605 views

How does one measure velocity in space?

Just what the title states. Velocity, by definition, is the distance covered in a defined amount of time. How does one measure the velocity of a spacecraft that is not in Earth Orbit? E.g. Beagle ...
362 views

What exactly are super WIMPs?

I recently got confused (and slightly annoyed by the lack of technical details) when reading a popular article (authored by Jonathan Feng and Mark Trodden) introducing the concept of super WIMPs. The ...
759 views

Why is the observed ratio of baryon to photon density considered too small?

Many descriptions about matter-antimatter asymmetry starts with the statement that observed baryon to photon density (about 6.1x10^(-10)) is too small. What is the reason? What ratio is expected?
807 views

Time and distance where velocity is a function of time

I'm creating a video game set in space in which spaceships travelling between places accelerate until they hit a maximum velocity. They then travel at that velocity until a time when they need to ...
2k views

study quantum mechanics without physics background [closed]

I am a first year PhD math student, and must decide: should I study Quantum Mechanics, although I don't have undergrad background in Physics? Let me be more specific about my situation: Background: ...
544 views

Variations of double slit experiment with their results to look up

Are there variations of double slit experiment with their results to look up? for example besided the two parallel slits, having two holes or two slits at 90 degree angles?
667 views

The meaning of Goldstone boson equivalence theorem

The Goldstone boson equivalence theorem tells us that the amplitude for emission/absorption of a longitudinally polarized gauge boson is equal to the amplitude for emission/absorption of the ...
221 views

Non-localities in Wilsonian effective action

Why terms non-analytical dependent on momenta in the effective action (in momentum space) are non-local? How to see this directly?
202 views

Does light photons have jerk? [duplicate]

While searching in web regarding whether rate of change of acceleration is possible or not; I came across the concept of jerk. I want to know whether photons which can be accelerated can also have ...
3k views

Can x and y axis have different scales? [closed]

In a graph on reflection, can i give the x axis a scale of 4 cms = 10 degrees , and the y-axis a scale of 2 cms = 10 degrees? Will it affect the readings?
1k views

what is the 2D gravity potential?

In 3D, I can calculate the total force due to gravity acting on a point on the surface of the unit sphere of constant density, where I choose units so that all physical constants (as well as the ...
617 views

What is the spectrum of the Hamiltonian of the universe?

Let us assume that there exists a Hamiltonian that (together with the initial state) describes the whole universe. Then my question is : What is the spectrum of this Hamiltonian and what are the ...
329 views

Are the higher-order terms in the series for energy really negligible?

To show that energy in special relativity reduces to $E=m+mv^2/2$ for low velocities, if we make a Taylor expansion of $m\gamma$ around $v=0$ we get $$E=m+mv^2/2+3mv^4/8+\cdots$$ But why can we cutoff ...
765 views

Frequency Specific Sound Reduction And dB Levels?

I started with a DIY construction project pertaining to sound-proofing; but now I'm feeling overwhelmed by a lack of knowledge on the physics of sound. I've learned that sound reduction techniques ...
230 views

Gauge symmetry description for $\phi^4$?

That is a follow-up to this question: Gauge symmetry is not a symmetry? Ok, gauge symmetry is not a symmetry, but ... ... a redundancy in our description, by introducing fake degrees of freedom ...
257 views

Force due to combination of free space and dielectric

I will make a generalized form of my question. There are two point charges $q$, $x$ distance apart. And there is a dielectric slab of thickness $t$ and of dielectric constant $K$. Should the force ...
571 views

Why don't most physics programs study the primary sources?

Why don't most physics programs study the primary sources? In other words: Why don't they include Newton's Principia, Lagrange's Analytical Mechanics, etc., in the curricula?
125 views

What is surface plasmon of metal nanoparticles?

I really want to understand about the Surface Plasmon of metal nanoparticles, if anyone can explain it to me i'll be grateful. I have checked Wikipedia for it but didn't get anything clear.