0
votes
3answers
271 views

A force's magnitude

In this question I asked about gravity and in the answers it came up that the magnitude is equal (of the gravity acting on the Sun and the of the gravity acting on the Earth) Does magnitude simply ...
12
votes
2answers
355 views

How are the northern lights produced?

Although I've never seen it myself, I hear the northern lights are a sight to be seen! I know they're related to the Earth's magnetic field but I don't know much more about them. What is the physical ...
12
votes
5answers
1k views

What are some useful ways to imagine the concept of spin as it relates to subatomic particles?

The answers in this question: What is spin as it relates to subatomic particles? do not address some particular questions regarding the concept of spin: How are some useful ways to imagine a ...
4
votes
2answers
477 views

Law for tap water temperature

I was wondering if anyone put together a law to describe the rising temperature of the water coming out of a tap. The setup is fairly simple: there's a water tank at temperature T, a metal tube of ...
17
votes
4answers
3k views

Boiling water and salt

I would like to have a good understanding of what is happening when you add salt to boiling water. My understanding is that the boiling point will be higher, thus lengthening the process (obtaining ...
4
votes
1answer
125 views

Reference request: statistical inference with real world (chaotic) data, e.g. climate/weather data

I'm interested in the process that goes from, for example, huge data sets of temperature, pressure, precipitation etc readings to a model of the atmosphere. I'd like to know about how much relies on a ...
13
votes
5answers
815 views

Speed of neutrinos

Everyone knows it is close to $c$, but how close? What are the recent results?
6
votes
2answers
677 views

Deuterons can share quantum states, but why it is fine for the protons and neutrons inside?

Deuteron (2H) is composed of a neutron (spin-1/2) and a proton (spin-1/2), with a total spin of 1, which is a boson. Therefore, it is possible for two deuterons to occupy the same quantum state. ...
17
votes
2answers
1k views

If the LHC doesn't find the Higgs Boson, what would be the implications for the Standard Model?

What would be the implications to the Standard Model if the Higgs Boson hadn't been found with the LHC? Also, if the Higgs Boson had not been found with the LHC, would it have been successfully ...
2
votes
1answer
594 views

Why is GNUplot so pervasive in Physics when there are much more modern tools? [closed]

First, I want to say upfront that this question need not dissolve into arguments and discussion. This question can and should have a correct answer, please don't respond with your opinions. GNUplot ...
20
votes
2answers
3k views

How does one measure the mass of a galaxy? And other such large quantities

Trained as a pure mathematician, I see claims about the mass of a galaxy and other such huge measurements that are arrived at experimentally, and I just have to scratch my head. I know this is a bit ...
21
votes
7answers
4k views

Is (rest) mass quantized?

I learned today in class that photons and light are quantized. I also remember that electric charge is quantized as well. I was thinking about these implications, and I was wondering if (rest) mass ...
4
votes
1answer
563 views

Mathematica to help for an Hamiltonian problem

I have an Hamiltonian problem whose 2D phase space exhibit islands of stability (elliptic fixed points). I can calculate the area of these islands in some cases, but for other cases I would like to ...
12
votes
9answers
6k views

Book about classical mechanics

I am looking for a book about "advanced" classical mechanics. By advanced I mean a book considering directly Lagrangian and Hamiltonian formulation, and also providing a firm basis in the geometrical ...
9
votes
8answers
15k views

Is gravity a force and if so what is its opposite?

For every force there is an equal force in the opposite direction on another body, correct? So when the Suns gravity acts on Earth where is the opposite and equal force? I also have the same ...
7
votes
1answer
486 views

Production of antiproton at the Tevatron

The Tevatron is a proton-antiproton collider; it collides a beam of protons against a beam of antiproton. I can understand how we obtain the protons, but for the antiprotons ? How are they produced ? ...
5
votes
1answer
265 views

How is it possible to calculate the energy liberated by a given fission process?

How is it possible to calculate the energy liberated by a given fission process? For example, in the fission of a $^{235}$U induced by capturing a neutron?
7
votes
1answer
450 views

Obtaining isotope stability

For a given isotope, one can obtain the binding energy using the semi-empirical mass formula. For example, has a binding energy of 1782.8 MeV. From this information, how can the likelihood of the ...
7
votes
3answers
463 views

What current alternatives are there to the standard concordance model of cosmology?

The current "standard model" or concordance model of cosmology is Lambda CDM which includes late time acceleration due to a cosmological constant, cold dark matter as the missing matter component and ...
16
votes
4answers
2k views

What ways are there to measure the local polarization of a laser beam?

Measuring the polarization of a laser beam is a simple enough task if the polarization is the same everywhere. You can even buy commercial polarimeters. How do you go about it if the light beam has ...
43
votes
5answers
3k views

Does Coulomb's Law, with Gauss's Law, imply the existence of only three spatial dimensions?

Coulomb's Law states that the fall-off of the strength of the electrostatic force is inversely proportional to the distance squared of the charges. Gauss's law implies that a the total flux through a ...
16
votes
3answers
2k views

Is it possible that all neutron stars are actually pulsars?

I'm assuming that what I've been told is true: We can only detect pulsars if their beams of electromagnetic radiation is directed towards Earth. That pulsars are the same as neutron stars, only that ...
16
votes
6answers
2k views

Is Newton's Law of Gravity consistent with General Relativity?

By 'Newton's Law of Gravity', I am referring to The magnitude of the force of gravity is proportional to the product of the mass of the two objects and inversely proportional to their distance ...
9
votes
3answers
465 views

What's with the very slightly larger mass of the neutron compared to the proton?

Neutron mass: 1.008664 u Proton mass: 1.007276 u Why the discrepancy? On a related note, how does one go about measuring the mass of a neutron or proton, anyway?
10
votes
3answers
1k views

How is squeezed light produced?

Ordinary laser light has equal uncertainty in phase and amplitude. When an otherwise perfect laser beam is incident onto a photodetector, the uncertainty in photon number will produce shot noise with ...
12
votes
10answers
1k views

Is quantum entanglement mediated by an interaction?

You can get two photons entangled, and send them off in different directions; this is what happens in EPR experiments. Is the entanglement then somehow affected if one puts a thick slab of EM ...
19
votes
7answers
4k views

Why do neutrons repel each other?

I can understand why 2 protons will repel each other, because they're both positive. But there isn't a neutral charge is there? So why do neutrons repel? (Do they, or have I been misinformed?) The ...
4
votes
2answers
724 views

Mnemonics to remember various properties of materials

I'm trying to figure out how to remember that hardness: how resistant it is to deformation toughness: how resistant it is to brittle failures stress: force on a surface area strength: ability to ...
15
votes
2answers
670 views

How do physicists use solutions to the Yang-Baxter Equation?

As a mathematician working the area of representation of Quantum groups, I am constantly thinking about solutions of the Yang-Baxter equation. In particular, trigonometric solutions. Often research ...
8
votes
1answer
188 views

Proton therapy in cancer treatment

Why are protons used in cancer therapy ? Is there any advantages compared to classics X-rays treatment or electron treatment ?
15
votes
2answers
2k views

What is an intuitive explanation of Gouy phase?

In laser resonators, higher order modes (i.e. TEM01, etc) accumulate phase faster than the fundamental TEM00 mode. This extra phase is called Gouy phase. What is an intuitive explanation of this ...
11
votes
6answers
1k views

What causes polarised materials to change colour under stress?

Our physics teacher showed the class a really interesting demonstration. He used two polarised filters in opposite orientations, then he took some antistatic tape and stretched it under the two ...
10
votes
4answers
2k views

Why is the LHC circular and 27km long?

The LHC in Geneva is a circular accelerator, 27 km long, why is it like that ?
6
votes
1answer
4k views

How do 2 magnets spin by themselves if positioned precisely?

A few years ago I went to a museum, where there was a board with 2 bar magnets, on a pole each so they could rotate. If you rotated them so the lined up with the same poles (N) facing each other, ...
8
votes
2answers
286 views

What is a capacitive screen sensing?

What should be a properties of a body so a contact with it can be detected by a capacitive touchscreen or a touchpad?
8
votes
3answers
630 views

Impressions of Topological field theories in mathematics

There have been recent results in mathematics regarding Conformal field theories and topological field theories. I am curious about the reaction to such results in the physics community. So I guess a ...
6
votes
2answers
258 views

How to check Einstein-like equations on their correspondence with the real world?

Physicists studying the grounds of physics and some mathematicians often come to a theories which are like a general-relativity, but do not coincide with it. Often these theories contradict the real ...
12
votes
5answers
10k views

Where do magnets get the energy to repel?

If I separate two magnets whose opposite poles are facing, I am adding energy. If I let go of the magnets, then presumably the energy that I added is used to move the magnets together again. However, ...
16
votes
3answers
796 views

How to show that the Coriolis effect is irrelevant for the whirl/vortex in the sink/bathtub?

There is a common myth that water flowing out from a sink should rotate in direction governed by on which hemisphere we are; this is shown false in many household experiments, but how to show it ...
10
votes
4answers
879 views

Lay explanation of the special theory of relativity? [closed]

What is Einstein's theory of Special relativity, in terms a lay person can follow?
7
votes
6answers
135k views

How to calculate average speed [closed]

I recently encountered a puzzle where a person drove 120 miles at 40mph, then drove back the same 120 miles at 60mph. The average of the speeds is (40mph+60mph)/2 = 50mph, so the total trip time ...
33
votes
10answers
1k views

What is the difference between a measurement and any other interaction in quantum mechanics?

We've learned that the wave function of a particle collapses when we measure a particle's location. If it is found, it becomes more probable to find it a again in the same area, and if not the ...
5
votes
4answers
517 views

Velocity of Object from electromagnetic field

I am wondering if someone could provide me with a formula that would tell me at what velocity a projectile can be launched from something using an electromagnetic field. The idea is much like a rail ...
14
votes
8answers
4k views

Does leaning (banking) help cause turning on a bicycle?

I think it's clear enough that if you turn your bicycle's steering wheel left, while moving, and you don't lean left, the bike will fall over (to the right) as you turn. I figure this is because the ...
6
votes
4answers
390 views

Monte Carlo use

Where is the Monte Carlo method used in physics?
5
votes
3answers
2k views

How's the energy of particle collisions calculated?

Physicists often refer to the energy of collisions between different particles. My question is: how is that energy calculated? Is that kinetic energy? Also, related to this question, I know that the ...
24
votes
4answers
2k views

Why does the sky change color?

Why the sky is blue during the day, red during sunrise/set and black during the night?
142
votes
11answers
20k views

What experiment would disprove string theory?

I know that there's big controversy between two groups of physicists: those who support string theory (most of them, I think) and those who oppose it. One of the arguments of the second group is ...
9
votes
4answers
13k views

What is sound and how is it produced?

I've been using the term "sound" all my life, but I really have no clue as to what sound exactly is or how it is created. What is sound? How is it produced? Can it be measured?
26
votes
5answers
3k views

Hamilton's Principle

Hamilton's principle states that a dynamic system always follows a path such that its action integral is stationary (that is, maximum or minimum). Why should the action integral be stationary? On ...

15 30 50 per page