5
votes
1answer
258 views

Earth-Moon orbiting each other after being engulfed by Red Giant

Recently some exoplanets were discovered which are thought to be the leftover cores of giant planets that had survived a star becoming a Red Giant and then shrinking back to a subdwarf. If giant ...
-1
votes
1answer
94 views

Tunnel through Ceres

Question edited: If you dig a tunnel through a large asteroid like Ceres along its axis of rotation and jumped in then what would be the first thing to stop you from falling back and forth along the ...
1
vote
1answer
100 views

Simulation of broken object

I was thinking and the following question came out: how an object that is falling is simulated once it hits the ground? Specifically, I would like to understand how one would be able to simulate the ...
0
votes
2answers
234 views

Train motion… Push or Pull?

While arguing against my friend today about the turbulence appearing between train's wheels. I told that the train pushes air aside during its motion through the tracks. But, he rejected it. Then, ...
3
votes
1answer
155 views

Is there any analogy between electron positron annihilation and brane anti-brane annihilation?

I would like to know if there is any similarity between electron positron annihilation and brane anti-brane annihilation? Is it there then can we use electron positron annihilation knowledge to study ...
0
votes
1answer
678 views

Divergence of cross product of transverse component

If I define the vector as $V_i=V^T_i+V^L_i$ and the transverse part is defined by $$V^T_i=\Big(\delta_{ij}-\frac{\partial_i\partial_j}{\partial^2}\Big)V_j$$ then is is obvious that $\nabla.V^T=0$ as ...
1
vote
0answers
187 views

Describing the Higgs mechanism to non-particle physicists

I'm sure I'm not the only person with this problem at the moment. I have been asked to give a public (not quite public, scientists, just not physicists) about 'this Higgs boson thing'. I am trying to ...
1
vote
1answer
286 views

Why does an ice rink use a primary and secondary coolant?

A normal refrigeration cycle uses one coolant, so why does vapor compression cycle of an ice rink you a primary coolant and a secondary coolant?
5
votes
2answers
237 views

How does QM allow imaging of individual electron orbitals?

Question: Why does the uncertainty principle allow probing of characteristics specific to the electron orbital distribution? If you measure an electron's position/momentum, then after you measure ...
9
votes
6answers
3k views

Why is Light invisible?

Why can't we see light? The thing which makes everything visible is itself invisible. Why is it so?
1
vote
1answer
98 views

Do field and potential energy always come together?

Is energy directly due to a field always potential energy? Is potential energy always due to a field? From the two Wikipedia links: a field is a physical quantity that has a value for each ...
1
vote
2answers
422 views

Projectile Motion

I know the angle at which a projectile is launched, how far it needs to go, and also the maximum height. How can I find the initial velocity needed (disregarding air resistance)? Currently, I am ...
2
votes
1answer
2k views

Exotic Matter — What is it?

I have a conceptual understanding of some theoretical physics concepts, so without getting into the math, what is exotic matter? I have read some articles that say it is anything not normal, while ...
3
votes
1answer
222 views

Does cosmological horizon grow or decrease as it radiates?

Ron Maimon in many posts claimed that cosmological horizon is like a big black hole. Black holes decrease as they evaporate and their radius decreases as well. So what is with a cosmological ...
0
votes
1answer
165 views

The effects of nuclear warhead detonations on the Earth's environment and global warming

For years I have been hearing all sorts of conflicting information about global warming. Many say that scientists have proven that humans have been warming the Earth significantly with their actions. ...
8
votes
2answers
336 views

Why would a particle in an extra dimension appear not as one particle, but a set of particles?

I was reading an article in this months issue of Physics World magazine on the three main theories of extra dimensions and stumbled across something I didn't quite understand when the author began ...
8
votes
3answers
417 views

Is the commutation of all possible operators sufficient to identify a spacelike interval?

It has been claimed (e.g. here) and apparently already been established, that the interval $x - y$ being (called) "spacelike" implies that $\bigl[\hat O (x),\, \hat O' (y)\bigr]=0$ for any two (not ...
0
votes
1answer
11k views

How much work is needed to compress a certain volume of gas?

I want to know the formula (and what does the symbols stand for) for how much work is needed to compress a certain volume of gas?
4
votes
1answer
83 views

How can we have massive states of strings and CFT on the string worldsheet at the same time?

Ok, so we can have conformal invariance on a string world sheet. However, it is well known that to preserve conformal symmetry we require states to be massless. So how is it that string theories ...
1
vote
1answer
223 views

How to uncurve a black hole

How can you uncurve a black hole and thereby get at the stuff inside? The Big Rip as dark energy reaches its zenith at the end of the universe. If curvature is a quantum field that is a ...
0
votes
1answer
172 views

Is a new universe created when dark energy rips open a singularity?

Dark energy will tear everything apart, even black holes. Is a new universe created when dark energy rips open the singularity of a black hole ? And does the topology of the universe depend on the ...
0
votes
1answer
476 views

Space expansion looking like time dilation

Space looks like time depending on the motion of the observer so I was going to ask if space expansion was the same as the unfolding of time, but this was asked on physics.stackexchange before and the ...
5
votes
1answer
470 views

Why are solar eclipses more common in the southern hemisphere?

I've seen the claim that solar eclipses are more common in the southern hemisphere than the northern hemisphere and would like to understand why and if that is the case? Does it relate more to the ...
0
votes
1answer
646 views

How is tritium illumination possible without negative health effects?

Turns out there's tritium illumination - a tiny very strong plastic tube will be covered in phosphor and filled with tritium. Tritium will undergo beta decay and a flow of electrons will cause the ...
3
votes
2answers
228 views

Negatve mass inside a black hole

With Hawking radiation, one half of virtual pair falls into horizon and this particle has negative energy. What would an observer inside horizon observe when seeing negative particles ? How do these ...
22
votes
1answer
1k views

Why is the partition function called ''partition function''?

The partition function plays a central role in statistical mechanics. But why is it called ''partition function''?
1
vote
2answers
339 views

Quantum Mechanics- Antenna emitting electromagnetic radiation

Radio signals are being transmitted in a frequency of $ 8.4 \times 10^9 \text{s}^{-1} $ and being received by an antenna that is capable of receiving power of $ 4 \times 10^{-21} \text{Watt} $ ($ 1 \, ...
2
votes
2answers
2k views

Do the physics in the FlyBoard video make sense?

If you haven't seen the video of the FlyBoard, please have a look: http://www.youtube.com/watch?v=Cd6C1vIyQ3w&feature=youtube_gdata_player Yes, it's amazing, but do the physics make sense or is ...
3
votes
0answers
242 views

Pseudo scalar mass and Pure scalar mass

Since the only difference between pseudo scalar and a scalar term is just a change of sign under a parity inversion, is it possible that both of them be present in the same field and interact? For ...
2
votes
1answer
752 views

What is quantum decoherence?

There is some part called quantum decoherence, and I am not sure why it is so sophisticated area. (according to the definition I see, what it seems to say is some probability turning into what we ...
0
votes
2answers
140 views

Electric generators?

When a magnet passes through a copper coil and electricity is induced into the coil, is there a magnetic resistance on the magnet as it passes through the coil?
4
votes
1answer
219 views

Why are electric charges allowed to be so light but magnetic monopoles have to be so heavy?

My question is in two parts. What is the origin of the electric field from an electric charge and why electron can have so small mass? While on the other hand for a magnetic monopole to create a ...
-1
votes
1answer
340 views

Are all effects that change color perception examples of redshift/blueshift?

As defined by Wikipedia: In physics (especially astrophysics), redshift happens when light seen coming from an object that is moving away is proportionally increased in wavelength, or shifted to ...
3
votes
2answers
2k views

Why can't I evaporate water without wind, just heat? (not boiling,evaporating!) Or can I?

So here is the thing, I searched all over the internet for this but all the sources say that I need wind because the process of evaporation goes as follow: Water particles at the top layer with ...
3
votes
1answer
643 views

Pascal law with two connected cylinders filled with water, and 50kg stones at both their ends

If I have two connected cylinders filled with water, and 50kg stones at both their ends (pressing both ends of the water) how much weight do I need to add on one side so that one of the stones reach ...
2
votes
0answers
1k views

Why is the valence band maximum at the gamma point in the bandstructure view of dispersion relation?

Why is the valence band maximum for most semiconductors at the gamma point in the bandstructure view of dispersion relation
10
votes
3answers
2k views

What does the dual of a tensor mean (e.g. dual stress tensor in relativistic ED)?

I know what the dual of a vector means (as a map to its field), and I am also aware of of the definition a dual of a tensor as, $$F^{*ij} = \frac{1}{2} \epsilon^{ijkl} F_{kl}\tag{1}$$ I just don't ...
5
votes
4answers
2k views

Are the field lines the same as the trajectories of a particle with initial velocity zero

Is it true that the field lines of an electric field are identical to the trajectories of a charged particle with initial velocity zero? If so, how can one prove it? The claim is from a german ...
3
votes
1answer
1k views

Formulas for compressibility of solids

I am taking a course in mechanics this semester, as well as a course in reservoir physics. Both courses have sections devoted to pressure/compressibility of solids, but the formulas look slightly ...
1
vote
2answers
510 views

State-dependent diffusions: Fick's law vs. Fokker-Planck's, which and why?

Consider a "state-dependent diffusion": a diffusion process for which the diffusion coefficient $D(x)$ depends on the (stochastic) state $x$ of the system. (An example is provided by the diffusion of ...
1
vote
1answer
526 views

Do atoms expand with universe? [duplicate]

Possible Duplicate: Why space expansion affects matter? Why does space expansion not expand matter? As we know, the universe is expanding, galaxies are away from each other. But what ...
0
votes
0answers
602 views

Carnot Engine for Finite Reservoirs

Two solid, finite thermal reservoirs have temperatures of $T_1$ and $T_2$ respectively and an engine operates between the two. Assume $T_1 > T_2$ and that each reservoir has constant heat capacity ...
2
votes
4answers
379 views

How many years will the nuclear resources of Earth last for generating electricity?

We have plenty of nuclear reactors around the world. They are consuming nuclear resources of the Earth. Nuclear elements are scarcer than the other elements, aren't they? When are we going to run out ...
2
votes
1answer
137 views

Crystal magnetic response only skin deep?

The Hamiltonian for a single electron in a magnetic field reads $$H=\left(\frac{{\bf p}^{2}}{2m_{e}}+q_{e}\phi\right)+\mu_{B}\left({\bf \hat{L}}+g{\bf \hat{S}}\right)\cdot{\bf ...
4
votes
5answers
7k views

What are distinguishable and indistinguishable particles in statistical mechanics?

What are distinguishable and indistinguishable particles in statistical mechanics? While learning different distributions in statistical mechanics I came across this doubt; Maxwell-Boltzmann ...
6
votes
2answers
1k views

Can water be magnetized?

This may be a stupid question, so feel free to shoot it down. Assuming all atoms have a magnetic moment, I would assume the water molecule too would have a resultant magnetic moment; ergo, it may be ...
5
votes
2answers
476 views

The “official” mass of the sun as unit?

I'm searching for the "official" mass of the sun as a unit in astrophysics. The mass of the sun can be calculated by: $M_{\odot}=\frac{4\pi^2\times(1 \ \text{ua})^3}{G\times(1\ \text{year})^2}$ So ...
4
votes
1answer
165 views

What is the smallest amount of He you can use to cool a superconducting magnet?

This is an engineering question, but it is adressed to physicists who build accelerators. This question: An electromagnetic space elevator? notices that a NbSn superconducting ring around the equator ...
0
votes
1answer
734 views

What is the relationship between the Higgs field and quarks?

I have some difficulty considering the relative size of each and the meaning behind the shape of Higgs boson. I ask relating to the structures of both the Higgs field and quarks. How is it that the ...
9
votes
3answers
11k views

Does the human body have a resonant frequency? If so, how strong is it?

Inspired by this question on Music beta SE, I'm wondering if the human body has a strong resonant frequency. I guess the fact that it's largely a bag of jelly would add a lot of damping to the system, ...

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