# All Questions

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### Do protons in the beam on LHC interact with photons?

Do protons in the beam on LHC interact with photons? I wonder how a beam would look from outside. Is there a photo of a proton beam?
376 views

### From quantization under external classical gauge field to a fully quantized theory

Let me take QED for example to clarify my question: The textbook-approach(at least for Peskin&Schroeder) to quantize ED is to first quantize EM field and Dirac field as free fields respectively, ...
73 views

### Sunrise time across the globe?

This question is more astronomy related, I started thinking when I heard from one of my friends living in Jiamusi, that Sun rise at 02:00 and sets at 14:00, I know that this place is more near to ...
407 views

### How do we end up with a gravity-dominant macroscopic universe from a quantum world having weakest gravity?

At quantum scale, gravity is the weakest force. Its even negligible in front of weak force, electromagnetic force, strong force. At macroscopic scale, we see gravity everywhere. Its actually ruling ...
117 views

### How would a semi-classical particle react to the double slit experiment?

As far as I know, there is a smooth transition between quantum and classical regimes, so that even classical particle like a massive object has a wavefunction associated with it. However, the double ...
1k views

### Why is the (free) neutron lifetime so long?

A neutron outside the nucleus lives for about 15 minutes and decays mainly through weak decays (beta decay). Many other weakly decaying particles decay with lifetimes between $10^{-10}$ and $10^{-12}$ ...
1k views

### How can I calculate the flow rate necessary for a given cross sectional area, angle, and length

I'm making a toy for my kids and this problem came up. I have a channel on a slight angle (angle is between ground and length of channel) and I'm pouring water into it. I want to know how quickly I ...
929 views

### If electromagnetic fields give charge to particles, do photons carry charge?

As I understand these two statements: An electromagnetic field gives particles charge A photon is a quantum of electromagnetic field It must mean that a photon carries charge. But I guess it isn't ...
128 views

### Do human body parts like hands or legs move with uniform acceleration?

So, is this true? I mean, does a movement by hand or leg make uniform or constant acceleration?
554 views

### Why are the physical sciences described perfectly by mathematics?

Why are the physical sciences described perfectly by mathematics?
137 views

### Can entanglement be used to decrease entropy of two systems?

I know that entanglement can create correlation between systems. Would it be true to say that entanglement create constraints between systems? Can constraints be used to lower the total entropy of ...
333 views

### Neutron decay and electron anti neutrino $n\to p + e + \bar{\nu}_e$

Why do we need neutrino to explain neutron decay? Is there any evidence regarding existence neutrinos in the context of $n\to p + e + \bar{\nu}_e$?
1k views

### Maxwell's equations in microscopic and macroscopic forms, and quantization

The macroscopic Maxwell's equations can be put in terms of differential forms as $$\mathrm{d}\mathrm{F}=0,\quad\delta \mathrm{D}=j\implies \delta j=0,\quad \mathrm{D}=\mathrm{F}+\mathrm{P}.$$ ...
199 views

### What has been measured at the Higgs experiment and what do we know now?

Explained at the level of a 5$^{\text {th}}$ semester physics student (i.e. pre QFT, but far beyond the level of a news article for non-physicists, which avoids all details and only deals in ...
260 views

### Can a huge gravitational force cause visible distortions on an object

In space, would it be possible to have an object generating such a huge gravitational force so it would be possible for an observer (not affected directly by gravitational force and the space time ...
7k views

### How does electricity flow in conductor when potential difference is applied?

Electrons move from higher potential to lower potential. When a conductor is connected to battery, electron move from negative terminal to positive terminal. But the battery itself forms a Electric ...
99 views

### Painting wine botles [closed]

Yes, it's a physics related question. Read on. I know from general knowledge that in order to produce a decent wine, you must keep it in a dark place. Therefore, from my knowledge of physics I guess ...
360 views

### Why is ${\partial^i}{\partial_i\phi}$ = ${\partial^i {\phi}}{\partial_i{\phi}}$?

This notation can be found on page 254 of Victor Stenger's Comprehensible Cosmos and in David Tong's Lectures on QFT (Equation 2.4 http://www.damtp.cam.ac.uk/user/tong/qft/two.pdf), and in EDIT: on ...
577 views

### Instability of a thrown tennis racquet

Someone once mentioned to me that it's impossible to throw a tennis racquet (or similarly shaped object) into the air, perpendicularly to the string plane, in such a way that it won't turn. What is ...
734 views

### Higgs field requires a large cosmological constant — does the Zero Point Field balance it?

I just read Wolfram's blog post on the Higgs discovery. Still, there’s another problem. To get the observed particle masses, the background Higgs field that exists throughout the universe has to ...
3k views

### How can sound waves propagate through air?

We know that the sound waves propagate through air, and it can't travel through vacuum. so the thing that help it doing that is the air's molecules pressure. So my question how can that happens? I ...
348 views

### Speaker cabinet to improve sound of mobile phone loudspeaker (music) [closed]

I want to experiment with an enclosure for my phone so the frequency response has a little more punch at the bottom end. I understand that something can't be created from nothing, but enclosures work ...
132 views

### Deviation from power law distribution of earthquakes

One of the most accepted frameworks for the relationship between the magnitude and frequency of an earthquake is that of the critical phenomena. In this framework, the magnitude of events must be ...
935 views

### If quarks didn't have mass, could protons (and neutrons) exist?

I read here (mass of a proton) that the mass of a proton is mostly (99%) due to the energy of the strong nuclear force which binds the quarks together, and not the actual mass of the quarks. My ...
167 views

### Hilbert of quantum gravity: bulk $\otimes$ horizon

I was reading a paper dealing with the Hilbert of quantum gravity (or more precisely what should it look like considering what we know from QM and GR) ref: http://arxiv.org/abs/1205.2675 and the ...
270 views

### Intensity of unpolarized light

If the electromagnetic field of an unpolarized plane wave is written as $$\bar{E}(t,\bar{x})=(\bar{E}_{0x}+\bar{E}_{0y}e^{i\delta(t)})e^{i(\bar{k}\bar{x}-\omega t)}$$ ...
190 views

### How to define a field? [duplicate]

Possible Duplicate: What is a field, really? What are electromagnetic fields made of? What is a field ? What is magnetic field or other fields made of or what it is, How do u define it ...
313 views

### Using Moments to influence the thickness of beams in structure?

Are moments relevant to the thicknesses of beams in a structure (ie. the larger the moment the thicker the beam)?
472 views

### Adding rotation to internal coordinates

I'm optimizing the geometry of a system composed of several interacting masses (a molecule). The energy of the system depends on the relative position of the masses, and all velocities are zero. In a ...
4k views

### How do photons travel at a speed that should be impossible to attain?

If it requires infinite amount of energy to travel at the speed of light then how photon attains this speed? Its source is never infinitely sourced.
449 views

### what does it mean for a particle with no size to have angular momenta?

I recently was reading about higgs boson and particle spin recently and I stubble upon an question that contains an answer to what a spin is. It explains that electrons etc. have no size yet they ...
167 views

### From where this number of 14 Tev has arised for proton-proton head on collision in LHC?

I am interested in finding out, why are collisions at 14TeV done in the LHC, instead of some other energy?
201 views

### Why don't cancelling wavefunctions for two different particles give zero total wavefunction?

Let $\left|a\right>=e^{i(kx-\omega t)}$， $\left|b\right>=-e^{i(kx-\omega t)}$ be two neutral particles in the 1D free space without any interaction. Then ...
2k views

### What does it really mean that particle has a spin of up/down? And how is spin actually meassured?

I been reading some physics articles (related to the recent discovery of the particle that could be a Higgs boson) posted online and it was talking about electron spin and how it can only have values ...
293 views

### Why did Standard Model never sense a requirement to include gravitational quantum? [closed]

Standard Model is advanced (lorentz invariant) version of Quantum physics. It tried to include everything which came in the way while understanding quantum world. It even didn't bother to include ...
674 views

### Is the Higgs mechanism a fundamental interaction?

Is the Higgs mechanism a fundamental interaction of the same standing as the strong, weak and electromagnetic interactions? If not, is it mediated by the weak interaction? It seems that all the ...
2k views

### How long was a day at the creation of earth?

Since the earth is slowing its rotation, and as far as I know, each day is 1 second longer every about 1.5 years, how long was an earth day near the formation of earth (4.5 billion years ago)? I ...
4k views

[This question is Certified Higgs Free!] Richard Feynman in Lectures on Physics Vol. II Sec. 17-4, "A paradox," describes a problem in electromagnetic induction that did not originate with him, but ...
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### Does relativity apply to something experiencing Centripetal forces?

If I tie a rope to a clock and spin it over my head, would it lose synchronization with a clock sitting at my feet?
380 views

### Does field energy create rest mass in QFT theories?

The central importance of Higgs boson would be that the Higgs mechanism gives rest mass to fundamental particles. It seems like a very natural argument that fundamental particles need to be given ...
621 views

### Higgs field questions

The Wikipedia article about Higgs field poses some questions to me. The article says that the Higgs field is a "nonthermal" field, a field whose energy does not decrease as the universe expands, ...
486 views

### Angular momentum components as independent integrals of motion

I was told that in order to solve the Kepler problem (6 degrees of freedom in total) you have to proceed, step by step, to reduce those degrees of freedom using the integrals of motion. You do so ...
1k views

### How can electric displacement vector field is equivalent to flux density on free space

Wikipedia states that "In free space, the electric displacement field is equivalent to flux density, a concept that lends understanding to Gauss's law". Doesn't that meant that at free space ...
135 views

### Can I transfer vibration with hydraulics?

I need to transfer vibration to 10 meters. I can do this with solid metal rod, but its making mechanical design complex. So, I am thinking to do it hydraulically (tubes can easily be bend). But, I am ...
213 views

### How can a pion have a mass, given it's a “field mediator” and created/destroyed continuously?

Maybe some of my assumptions here are basically wrong, but isn't it true that pion is the "mediator" for the strong force field. the quantum field theory basically says that there are no fields, ...
850 views

### Temperature dependence of resistivity in metals

We know that in high temperature, resistivity in metals goes linearly with temperature. As temperature is lowered, resistivity goes first as $T^5$ due to "electron-phonon" interaction, and then goes ...
85 views

### Remaining Potential Experimental Particle Physics Discoveries at the TeV Scale?

With the discovery of the Higgs Boson, some have been calling it the end of experimental particle physics for our generation, due to the fact that all of the particles predicted by the standard model ...
332 views

### Does Standard Model confirm that mass assigned by Higgs Mechanism creates gravitational field?

I am not comparing passive gravitational mass with rest inertial mass. Is there an evidence in Standard Model which says that active gravitational mass is essentially mass assigned by Higgs mechanism. ...