1
vote
1answer
522 views

Determining wave function for term symbol 1D

I am trying to follow a book (Introduction to Ligand Field Theory by Ballhausen in 1962 on pg 15), but it isn't clear how they make a particular leap. Background I want to find the wave function for ...
2
votes
2answers
286 views

Might the LHC see nothing new at all?

There's no guarantee that supersymmetry (or more exotic new physics) will be seen at the LHC. Meanwhile, it's standard lore that a Higgsless standard model becomes nonunitary somewhere in the vicinity ...
6
votes
3answers
2k views

Popular books on QM

After some discussions with my friend about some "popular" aspects of quantum mechanics, my friend asked me whether there exist any books that could convey the basic ideas in a non-technical way (my ...
3
votes
4answers
356 views

existence of other forces obeying inv square law

Is there any restriction in what we know of physics to the existence of other type of forces that obey the inverse square law in 3 dimensions. I mean other than electromagnetic and gravitational. ...
2
votes
4answers
222 views

What could cause a planet to have apparently random season lengths?

The world A Song of Fire and Ice series is set on is characterized by seasons that last several years (how years are measured on this planet is not specified to my knowledge). However, they are of ...
6
votes
3answers
937 views

Is it possible to make a hydrogen-alpha solar scope?

Is the construction of an etalon / Fabry-Pérot interferometer within the reach of amateur telescope makers? Are there any resources pointing to such projects?
2
votes
2answers
529 views

How do you find conserved quantities for linear second order ODEs?

I have a differential equation of the form $ \frac{d^2 y}{dt^2} + f(t) \frac{dy}{dt} + g(t) y = 0 $ where $f$ and $g$ are known functions of time. Is there a systematic (or otherwise) way of ...
5
votes
2answers
177 views

Photon absorption

[sorry, this way below the level of this forum -- flames are most welcome] When a photon is absorbed by a piece of matter that does not reflect it -- where does the photon "go"? Eg, one shines light ...
2
votes
1answer
4k views

calculating thermal energy [exam prep]

I'm preparing for a grade 11 physics exam but having trouble with a question: a 19.9kg mass slides in a straight 28.8m line experiencing friction with a coefficient of 0.105, how much thermal energy ...
3
votes
3answers
162 views

What was the apparent magnitude of the June 15th 2011 lunar eclipse?

My plan was to observe and estimate the apparent magnitude of the Moon during totality of the June 2011 lunar eclipse, but the clouds rolled in at the exact moment, so I couldn't make any useful ...
5
votes
0answers
334 views

Derivation of the oil drop experiment [closed]

The oil drop experiment performed by Robert Millikan in 1909 enables us to calculate the elementary charge. The following forces have effect on the droplet: $F_\mathrm{G} = m g = \frac{4}{3} \, \pi ...
7
votes
4answers
1k views

Which derivative with respect to time is which in the Heisenberg picture of quantum mechanics?

For an observable $A$ and a Hamiltonian $H$, Wikipedia gives the time evolution equation for $A(t) = e^{iHt/\hbar} A e^{-iHt/\hbar}$ in the Heisenberg picture as $$\frac{d}{dt} A(t) = \frac{i}{\hbar} ...
10
votes
2answers
353 views

Silicon-based life [closed]

My question may not be suitable here, because it's more of astrobiology. Life as we know it is carbon based. Is life based on silicon possible? What would the conditions for habitability for ...
3
votes
4answers
1k views

What do we consider “Perpetual Motion”

I know this is a bad question to most serious Physics but I have a question about what is considered “Perpetual motion.” The Foucault pendulum in the UN consists of sphere that passes directly over a ...
2
votes
2answers
293 views

a question on Lagrange's equation when the time derivative of the generalized co-ordinates is constant

Consider a system whose generalized co-ordinates are $q_i$ and is under the constraints $\dot{q_i} = K_i \forall i = 1,2,3,...$ where $K_i$ are constants. I have a problem in writing the Lagrange's ...
1
vote
0answers
130 views

Where does light energy go when the electric and magnetic components equal zero? [duplicate]

Possible Duplicate: Popular depictions of electromagnetic wave: is there an error? The electric and magnetic components of light increase and decrease at the same time, pass through zero ...
7
votes
5answers
1k views

proof of gauge invariance for quantum 1D ring

This is a question on gauge invariance in quantum mechanics. I do some simple math on a 1D wave-function with periodic boundary conditions, and get that gauge invariance is violated. What am I doing ...
1
vote
1answer
183 views

What software can I use to simulate supersonic gas particle flow? [closed]

Please please help me out with this. I am trying to find a software/program that I could use the simulate the scattering effect of light when it strikes gas particles moving at supersonic speeds? ...
6
votes
1answer
275 views

Superpartner for the stress-energy tensor

I would like to understand what is meant when one introduces a generator $G(z)$ as the superpartner of the energy-momentum tensor $T(z)$. How does one decide that this $G(z)$ should have a ...
6
votes
5answers
1k views

Why do blades of windturbine propellers as comp. to propellers of ships cover very different areas?

This is a thought I asked myself often, but never did real efforts to get an answer. Barsmonsters question about number of fans of a wind turbine made me think of it again Why do blades of aircraft ...
7
votes
1answer
246 views

Could two colliding comets near Earth cause devastation?

Let's say two comets crashed into each other. If it was 0.1 AU away from the Earth, would the collision cause mass destruction here, or not affect us at all?
2
votes
2answers
2k views

Do we know exactly how fast we are going relative to the center of the galaxy

I mean total inertial on my body siting here at my computer "California US." Ok so the earth is rotating on its axis and in turn around the sun and the sun around the galaxy. The object the question ...
5
votes
1answer
121 views

Sum of angular momentum of all electrons in a magnet

Can the sum of angular momentum of all rotating electrons in all the aligned atoms in a permanent magnet have a significant contribution to the macro angular momentum of the magnet? If yes, why does ...
3
votes
4answers
2k views

Outcomes of earth slowing down spinning on its own axis

What are the possible outcomes if earth slows down spinning on its own axis? To be specific: Can the decrease in the internal centrifugal (or centripetal) force due to slowing down earth's spin: ...
1
vote
2answers
176 views

Optimum magnet layout for tripping a coil sensor

If I had say a dozen or so small bar magnets and I wanted to used them to trip the traffic light sensors (which are a coil embedded in the road where a vehicle would stop for the lights), what would ...
4
votes
1answer
311 views

Electric potential energy in curved space-time

In flat space-time the electric potential energy between two charges is $\frac{k Q_1 Q_2}{r_{12}}$, where $Q$'s are charges and $r_{12}$ is the distance between them. What would happen if the two ...
3
votes
2answers
5k views

Analyzing the motion of a ball rolling without slipping inside a hemispherical bowl

Consider a solid ball of radius $r$ and mass $m$ rolling without slipping in a hemispherical bowl of radius $R$ (simple back and forth motion). Now, I assume the oscillations are small and so the ...
2
votes
1answer
428 views

significance of maxima and minima of time varying kinetic energy of a system

Consider a system of particles where the kinetic energy of the system is varying with time. I'd like to know the significance (or meaning) of the time derivative of the kinetic energy being zero at a ...
8
votes
3answers
3k views

What would happen if the polar ice caps of Mars melted?

My dad told me that Mars' polar ice caps are made of H2O and CO2. If they melt, would it add an atmosphere to Mars and allow life?
2
votes
2answers
181 views

Thought experiment that seems to involve something growing at twice the speed of light. Is anything wrong?

Let foo be some unit of distance and bar be some unit of time which have been chosen so that the speed of light c = 1 foo/bar. Position several observers along a line each separated by one foo, and ...
10
votes
4answers
915 views

Two planets in same orbit - not planets?

Let us pretend for a moment that there are two identical planets that are exactly opposite their star from each other and are the same distance from said star. (This would make them, at all times, ...
10
votes
2answers
88 views

Planets capable of life: dead or still alive?

There are some planets that scientists speculate may be capable of supporting life. However, these planets are hundreds of light years away. How can we be sure they are still capable of supporting ...
-1
votes
1answer
122 views

the search for calabicles

Pop-sci ST books say, "At every point of space, there is a Calabi-Yau space..." or similar. But uncertainty p. and noncommgeom say, no points in space, only planckons (not my coinage). Is 'point of ...
6
votes
1answer
251 views

Parametrisation of general MSSM/SUSY based on collider experiment observables

The full MSSM contains 120 parameters. In SUSY searches, one usually picks a model like MSUGRA which makes a few assumptions and only has 5 free parameters like $m_0$, $m_{1/2}$, .... Now, I'm ...
18
votes
5answers
535 views

Why don't we have a better telescope than the Hubble Space Telescope?

The Hubble Space Telescope (HST) was launched in 1990, more than 20 years ago, but I know that it was supposed to be launched in 1986, 24 years ago. Since it only took 66 years from the fist plane to ...
3
votes
3answers
160 views

Distant bodies emitting photons

This comes from a discussion forum, where a friend of mine asked the following: We can see objects in space billion of light years away, right? I started wondering about that. If you take 2 ...
0
votes
2answers
585 views

In a 2D problem with a thrown object, why is the acceleration along the x-axis equal to 0?

I'm starting Physics, and I don't understand why the acceleration along the x-axis is zero for an object thrown near the surface of the Earth. This may be problem specific, but I wouldn't know since I ...
3
votes
2answers
587 views

the form of a kettle

What is the best form for a kettle, that is, to have the water boil the fastest? I am particularly interested in the following case: for one given kettle (whose volume is constant) containing ...
2
votes
3answers
2k views

How could I translate a field of view value into a magnification value?

When I zoom in with Stellarium, it indicates a field of view (FOV) value in degrees, but most binoculars and telescopes are advertised with value like "nX magnification power." How could I translate ...
2
votes
2answers
679 views

Nature of spacetime 4-vector and tangent space?

An entry level confusion about spacetime. I understand that a 4-vector describes a point or event in spacetime. But I've also read (Bertschinger, 1999) that re spacetime "we are discussing tangent ...
14
votes
2answers
916 views

What if our Sun were located in the middle of a globular cluster?

Say you took our current solar system and relocated it deep in the heart of a globular cluster such as Omega Centauri. What would the night sky look like? Would the starshine of nearby stars be enough ...
12
votes
3answers
13k views

How do we determine the mass of a black hole?

Since by definition we cannot observe black holes directly, how do astronomers determine the mass of a black hole? What observational techniques are there that would allow us to determine a black ...
15
votes
2answers
2k views

How does one experimentally determine chirality, helicity, spin and angular momentum of a fundamental particle?

If I've got an instance of a fundamental particle, how can I separate out the measurements of these four quantities? (I think) I understand the theory behind them, and why the particles in the ...
36
votes
2answers
3k views

Wind generators - why so few blades?

Why commercial wind generators usually have just 2-3 blades? Having more blades would allow to increase power OR decrease diameter. Decreased diameter would also reduce stress due to different wind ...
3
votes
1answer
873 views

How many electrons are displaced when combing hair?

Feynman talking about electricity: http://www.youtube.com/watch?v=qhh32JYkQPk When brushing your hair, Feynman mentioned that a "few" electrons were transferred to the brush (or vice versa, can't ...
12
votes
7answers
2k views

Can a particle be *physically* observed inside a quantum barrier?

I understand that a particle approaching a finite potential barrier with $E < V_0$, there still is a probability of finding the particle on the other side of the barrier due to quantum tunneling. ...
4
votes
3answers
128 views

How long would it take to scan the visible universe for unique signals?

The article Amazing rays as star succumbs to dark side talks about a very large black hole swallowing up a star. The report goes on to say that the only reason it was discovered was because it shot ...
11
votes
1answer
77 views

Why did the june 2011 lunar eclipse last so long?

It was kind of hard to miss the lunar eclipse this week, although I didn't see it in person (Sod's law means that on every relatively major astronomical event clouds cover where I am). From what I ...
1
vote
0answers
131 views

heliocentricity and the theory of relativity [duplicate]

Possible Duplicate: Why do we say that the earth moves around the sun? I should preface by stating that I'm not a physicist and my knowledge of the theory of relativity is limited to what ...
6
votes
1answer
54 views

Refraction and scattered light for NLCs

For helping with judging NLC candidates (are they NLC or not) I have a set of formulas to calculate the minimum altitude (in km) of the candidate given an observed altitude (in degrees) of the ...

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