All Questions

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Is there anyone calculate the probability of extrasolar planets?

After reading an recent news "Stargazers capture first picture of a planet with two suns – just like Luke Skywalker’s home planet of Tatooine in Star Wars", I am thinking that: can we calculate the ...
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How far apart are galaxies on average? If galaxies were the size of peas, how many would be in a cubic meter?

The actual number: How far apart are galaxies on average? An attempt to visualize such a thing: If galaxies were the size of peas, how many would be in a cubic meter?
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Ljapunov exponent of driven damped pendulum

I have written a computer simulation of the driven damped pendulum, pretty much as the one shown here, only that I did it Python. Next, I have found some parameters for which the pendulum behaves ...
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Equidistant coffee rings in a mug: pinning boundaries coupled with migration of solute or just sip volume?

I understand that you get coffee rings on a table as a result of solute migration (solutocapillarity) towards the pinning of the circumference of the coffee ring [Deegan et al.]. Below is an ...
2k views

Why a person with a further near point experience a larger magnification with a magnifier

Two people, Micah and Lyra, with different near points are equally close to an object. Both inspect the object through the same magnifier by holding the lens close to the eye. Micah's near ...
331 views

Water entering hole at a depth, surface tension

The following is the question that very commonly appears in all HS textbooks. A hollow sphere with a hole is taken to a depth of 40cm when the water starts entering the hole. if the surface tension of ...
215 views

Indistinguishable particles in quantum mechanics

If you have two particles of the same species , Quantum mechanics says that $\Phi_{m_{1},x_{1},p_{1},m_{2},x_{2},p_{2}}=\alpha\Phi_{m_{2},x_{2},p_{2},m_{1},x_{1},p_{1}}$ But I don't understand why ...
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Meaning of spin

I'm pretty astounded that I did not hear about this sooner, but in my course on QFT our professor told us that the concept of spin can be used to mean three things: Mechanical spin (apparently a ...
3k views

Units and Dimensions - Use of proportionality constant

In units and dimensions we learn about Establishing a Formula : (example) : to establish a relationship between T (Time Period) , m (Mass) , l (length of the string) and g(acc. due to gravity) - ...
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rate of change of spring potential energy $\frac{dU}{dt}$

Suppose we have a setup like this. In orange are two wooden sticks sort of things, and they are attached to the block of mass $m$(as usual) at a joint which is hinge type something. A similar ...
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In what direction does a frustrated magnetic moment get aligned?

Consider 3 layers of Ferromagnetic materials stacked on top of each other with appropriate spacer layers in between. Let the top and bottom layers be pinned to layers of Anti Ferromagnets adjacent to ...
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Is there a mechanism for time symmetry breaking?

Excluding Thermodynamic's arrow of time, all mathematical descriptions of time are symmetric. We know the arrow of time is real and we know the equations describing physics are real so is there any ...
204 views

Von Neumann Entropy: varying definitions

I have seen different authors define von Neumann entropy in different ways. In particular, some use the natural logarithm and others log to base 2. What is the reasoning for this? Does it make any ...
260 views

Breaking of a covalent bond

When a bond between two atoms is broken, why only one electron is released. Why not two? (as two electrons make up a covalent bond.)
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Free body diagram and Newton's second law

Two bodies of mass $m_1=50 \text{kg}$ and $m_2 = 10 \text{kg}$ are connected with a light rope through a pulley (no friction between the rope and the pulley). $m_2$ moves on surface with angle ...
1k views

What determines bubble locations in boiling water?

Something a little different to our usual fare. I was boiling a pan of water for cookery the other day, and got to wondering what caused the location of the bubble streams from the bottom of the pan. ...
3k views

How electrons act under rotating magnetic field?

I study Power Engineering in University. Today I asked my lecturer to explain me exactly how atom's electrons act under spinning rotor's magnetic field, that generated dynamic electricity. But he even ...
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Is Feynman's explanation of how the moon stays in orbit wrong?

Yesterday, I understood what it means to say that the moon is constantly falling (from a lecture by Richard Feynman). In the picture below there is the moon in green which is orbiting the earth in ...
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Does gravity slow the speed that light travels?

Does gravity slow the speed that light travels? Can we actual measure the time it takes light from the sun to reach us? Is that light delayed as it climbs out of the sun's gravity well?
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Identical fermions in the same quantum state

If we are to take two Hydrogen atoms and subject them to the same potential, then wouldn't both Hydrogen atoms be in the same exact quantum state? This bother me because no two identical fermions can ...
605 views

Third-order phase transition in Landau theory

$F=\frac{a}{2}m^2+\frac{u}{4}m^4+\frac{v}{6}m^6-hm$, where F is the free energy, m is the order parameter, h is the external field, $a=a_0(T-T_c)$, and $a_0>0,u>0$ and $v>0$.We know this free ...
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Force analysis of silver atom in Stern–Gerlach experiment

In this experiment we only consider the force at z direction, but $\vec B$ field gradient doesn't exclusively exist at z direction according to Maxwell's equations. So why don't we see the splitting ...
247 views

Definition of energy

What is the definition of energy $E$ given a dispersion relation $\omega=\omega(k)$ where $k=|\vec k|$ and $\omega$ is not necessarily linearly proportional to $k$? What about momentum $\vec p$? This ...
181 views

Is electron velocity at induction higher than in a wire?

When looking to the electrostatic induction on a microscopic level, do the electrons really move with high velocities or they move like when a current passes through the wire (slowly).
29k views

Why frequency doesn't change during refraction?

When light goes through one medium to another it's velocity and wavelength changes. Why frequency doesn't change in this phenomenon?
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Can an Anti nuclear atom be synthesised so it can neutralise the effect of nuclear atom [closed]

as we have studied that if the number of electron becomes equal to number of proton then that particle becomes neutral. so what will the energy or procedure required to break the chain reaction in ...
472 views

Do EM waves transmit spin polarization?

Suppose you have a normal dipole antennae (transmitter and receiver) . Spin polarized current (as opposed to normal current) is sent into the transmitter, it emits an EM wave and the Receiver receives ...
3k views

The temperature of photon and its energy

Do photons have temperature? If not, does it mean that photon lose energy while travelling through space? As the planets farther away from the sun are comparatively cooler than the one that are ...
455 views

What determines the sign of an image distance?

A lens placed at the origin with its axis pointing along the x axis produces a real inverted image at $x = - 24 cm$ that is twice as tall as the object. What is the image distance? Why ...
11k views

Why do objects accelerate as they fall?

Most importantly, what must change in order for the falling object to change its speed? Is it the distance to the centre of the planet? If you pull the earth away from the object as the object falls, ...
412 views

What is the speed of acceleration of the inflation of the universe?

Is the inflation speed of the universe accelerating or is it a constant speed of expansion proportional to distance between objects.
471 views

Are there theories that explain wave-particle duality?

I'm confused by the famous wave-particle duality mystery: When a particle is left unobserved, it acts like a wave and can explore all classically available particle trajectories simultaneously. By ...
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If we connect a block of p-type semiconductor only to a positive terminal, will it become positively charged?

Connect the positive terminal of a battery to a piece of p-doped semiconductor, say, silicon doped with boron. Will the terminal pull electrons out of the doped silicon, or equivalently, inject holes ...
1k views

Calculate Capacitance in Series AC Circuits?

I'm supposed to calculate the capacitance of an unknown capacitor in series, but I'm not sure exactly which equation to use. I know the voltage across the resistor (Vr), voltage across the capacitor ...
431 views

How do you calculate power at the focal point of a mirror?

I'm a Mechanical Engineering student and I'm working on my senior project, so I need help. My project is about designing a solar dish having a diameter of 1.5 meters and a focal length of 60cm. so at ...
311 views

A question about defining a classical CFT

This is kind of related to this, Defining a CFT using beta-functions So what would be the right definition of a CFT even classically? Is it true that classically one will call a theory scale ...
121 views

Where is the magnetic self energy term in $L$ for a charged particle in an electromagnetic field?

In the Lagrangian for a charged particle in an electromagnetic field $$L = \frac{1}{2}mu^2 - q(\phi - \frac{\vec{A}}{c}\cdot \vec{u})$$ the energy of the particle is contained in the kinetic term, ...
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Do magnets lose their magnetism/force when they attract/repel each other?

So yea, if two magnets attract/repel multiple times(A LOT) will they lose their magnetism? If they don't break during the whole process?
316 views

Will a football (soccer) diffract? [duplicate]

Apparently all objects have wavelike properties, so, if we kick a football (soccer ball, if you must) through a pair of posts, does the ball in any sense diffract? If this is ridiculous then let me ...
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Polarizability and the Clausius-Mossotti Relation

There seems to be a fairly large inconsistency in various textbooks (and some assorted papers that I went through) about how to define the Clausius-Mossotti relationship (also called the ...
I know how and why we use this form of stationary Schrödinger equation for finding $\psi$ outside the finite square potential well: $$\frac{d^2 \psi}{dx^2}=\kappa^2 \psi$$ I Also know that the ...