# All Questions

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### Is the Graveyard Really so Serious?

Calculations in relation to black holes are solely in consideration of spacetime curvature and its effects. They are in total alienation with respect to the action of inertial agents[external ...
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### What makes a space a real space?

By "real space" I mean a space in which physical particles move. Consider a color sphere and let a bunch of objects "move" on its surface. "Move" means "change colors". Let there be some rules ...
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### Free 'fall' on an Inclined Plane

I guess we can say that two identical balls on the same inclined plane with different heigths reach the ground at the same time. So, who was the first one to observe it?. ...
336 views

### Faster than light possibility? [duplicate]

According to general relativity, speed is relative, so for example if you are running at 20 km/h and a car passes you at 30 km/h, the runner is actually moving at 50 km/h relative to the car. Now ...
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### From where we can view earth moving?

Earth moves with a speed around $100000 \,\,km/h$, which will be amazing, but from where we can see that moving speed? If we far away from earth (outside of earth gravity) then can view its moving? is ...
118 views

### Doing a Gaussian Integral [duplicate]

When you integrate over p you get: by using What are the steps to this? Do you integrate by parts?.
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### diffrent elements from diffrent elements [closed]

Do we get elements from other elements ? Somebody said they believed the world was visited by aliens and they made slavs of us and then amde us mine gold for them then they leave us to grow into what ...
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### Are shadows underwater “wet”? [closed]

Sorry if this is the wrong place to post this but it seemed the most appropriate. I read a riddle earlier today that mentioned something about shadows underwater and it got me thinking.. Would a ...
16k views

### Why current through all the resistors in series is considered to be same? [duplicate]

Consider the circuit shown, where $R_{1} > R_{2}$. I meant to say that resistance offered by the resistor 1 is greater than the resistance offered by the resistor 2. Keep $t$ constant i,e ...
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### Where in, Einstein’s “On the Electrodynamics of Moving Bodies” (Relativity), is “Time” reasonably shown to exist, or why is it a valid assumption? [closed]

Given the widespread acceptance that “Einstein’s Relativity” reasonably proves the existence of Space-‘Time’, and thus “Time”... Can any member of the Physics StackExchange please show precisely ...
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### Is Pluto made out of ice? [closed]

Is Pluto made out of ice--as in frozen water? If so, wouldn't that provide evidence for alien life in the cosmos?.
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### Why objects of different masses accelerate at the same speed under gravity [closed]

If you push massive object it accelerates slowly compared to object which is of same size but less density/mass. However, all objects do Accelerate at the same rate. ...
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### Is there any other mathematical tool to measure velocity, instead useing derivative? [closed]

To measure velocity we use derivative $$v=\frac {dr}{dt}.$$ Is the any other mathematical tool to do this?.
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### There can be nothing with zero mass [closed]

Zero mass has no meaning and is an outcome of 2nd postulate of STR .The STR can be developed without this postulate and thus the postulate is redundant besides being contradictory to 1st postulate.The ...
973 views

### Is velocity of light constant? [duplicate]

There is a difference between the concept of the speed of light and the velocity of light. are both of them constant ($dc=0$ and $dv_c=0$)? if yes, why?.
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### Which is the heaviest elementary particle? [closed]

Which elementary particle has the greatest rest mass? (For the sake of this question I'll call a photon's rest mass 0, whether it is or isn't [actually, tell me if this is the right thing to do]).
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### Are there any causeless phenomena from the mainstream physical viewpoint? [closed]

EDIT: The orginal version did not produce any answers about physics. I know what life is, I have studied that for decades. I wanted to hear how the border between matter and spirit looks from the ...
314 views

### Can a sound like a sonic boom change a object like a wall? And how the light on the walls will be changed after a sound like this? [closed]

Can a sound like a sonic boom change a object like a wall? And how the light on the walls will be changed after a sound like this? .
205 views

### Does Anything Exixts? [closed]

I Mean that Does Anything In The Universe Exists By Means Of Quantum Mechanics...I Heard This From Someone But i wanna be sure that it is really true or what?.
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### What would happen if an unstoppable force hits an immovable object? [closed]

I realize that the question a rather large paradox, but I do wonder if such a thing were true what would happen, assuming that neither of these "objects" can be destroyed by each other?
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### if the universe is flat does it mean it exists only in our mind as math? [closed]

My dad, who is a retired mathematician, has this attitude, which I think we all have as kids, that ultimately reality is made of stuff. End of story. If you look around yourself in the world, ...
345 views

### Existence of a physics-god [closed]

In your opinion, what is the most cosmological or physics argument that may favor the existence of something like a god to produce a universe like ours and what is the most counter argument for that. ...
369 views

### Isn't searches for dark matter crazy effort? [closed]

There are a lot of crazy quests in astrophysics, one of them is searches for dark matter. How someone could observe dark matter while it is far away?
102 views

### Magnetar field energy density

According to Wikipedia a Magnetar... Earth has a geomagnetic field of 30–60 microteslas, and a neodymium-based, rare-earth magnet has a field of about 1 tesla, with a magnetic energy density ...
308 views

### Energy of resultant photons from meson decay

I am a little unsure how to answer the following question, Find the energies of two photons emitted in opposite directions along the pion's original line of motion if the pion has a r.m.e of 500MEV ...
68 views

### The transfer function of a linearized system in state-space representation

I have physical system that can be described by a non linear equation system. I would like to get the transfer function of the linearized system. Let $x(t)$ a state variable, $u(t)$ input and $y(t)$ ...
838 views

### How to motivate Schrödinger's Equation? [duplicate]

Schrödinger's equation is supposed to be a differential equation for the wave function of a particle. As I currently understand, De Broglie's hypothesis is a hypothesis that for particles there should ...
99 views

### Gravitational work

As far as I know gravitational work is independent from the path of the object, and I have an object that goes up on a inclined plane to a certain height, and than, after the object reaches the edge ...
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### How are momentum and position operators dependent on the chosen inertial frame?

How are momentum and position operators in quantum mechanics dependent on the chosen inertial frame of reference?
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### Need of vector potential in quantum mechanics

I need your opinions. Why is the vector potential of a magnetic field important (or even necessary) to quantum mechanics? Why it has to be defined everywhere? Is there any fundamental reason you can ...
906 views

### Hamilton-Jacobi equation with time dependent Hamiltonian

I was struggling with this exercise about Hamilton-Jacobi equation. I have to solve by menas of Hamilton's principal function the system with Hamiltonian: $$\tag{1} H=\frac{p^2}{2m}-mAtx$$ with $A$ ...
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### What's the physical interpretation of an arbitrary normal mode for masses and springs?

Consider the following system consisting of 3 masses and 4 springs : I have learned that this system posseses three normal modes, corresponding to its three natural frequencies, say ...
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### Would it be possible to Loschmidt reverse Wigner's friend using future technology?

Would it be possible to Loschmidt reverse Wigner's friend using future technology? Why or why not? Can a human be isolated in a decoherence shielded box? Can we have fine control over every single ...
84 views

### Propagation of uncertainty - proof that it is minimal

I am not really sure if this is the right SE community for this question, but, I swear, I haven't found any better. The problem is as follows: we have n distance sensors placed around a quickly ...
96 views

### Does reflected light change LED power consumption?

If I enclose an LED in "tin foil" so that the photons it gives off are reflected back to it, would the power consumed by the LED go down?
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### Condensed matter physics: the concept of holes [duplicate]

Is it possible to see an analogy between the holes and positron particle behavior? The holes are particles that behave oppositely to the electron in current conduction. So it is not the electron ...
135 views

### Negative frequency contributions for very short pulses?

I am wondering if very short optical light pulses can have a Gaussian envelope? When I describe the pulse shape with a Gaussian than the frequency distribution has also a Gaussian shape. But if the ...
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### How can one approximate integral def. of Z by the max value of the integrand?

I am taking a course in statistical physics, and while reviewing my notes from the lectures I came across something that I cannot get my head around. We arrive at an integral expression for the ...
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### Why don't the two forces balance each other In Newton 3rd law? [duplicate]

Why don't the two forces of action and reaction balance each other ? I imagine that although they are opposite forces, they have different points of application. Is this true?
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I have a system of particles (electrons) with an initial RMS energy spread (say "1"). It goes through a section of constant magnetic field (bend magnet) and the electrons radiate. The electrons lose ...
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### Reconciling two interpretations of renormalization

I know of two fascinating and perfectly reasonable explanations of renormalization. However, I'm having difficulty reconciling the two. The first is to say that when we initially write down a ...
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### Will terminal velocity exist on this imaginary planet?

If the atmosphere of an imaginary planet is really thin like 100 particles per cubic centimeter (density of the closest resemblance of vacuum made on Earth) and has mass say, 15 times than that of ...
316 views

### If the specific heat capacity depend upon the temperature, what formula we should use instead of $Q=mc\Delta T$

Recently, I learned that specific heat capacity is not constant in different temperatures and it depends on the temperature.If I have diagram like this (consider that the red part is a quarter of ...
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### Strong force and quantum tunnelling

I am well aware of how quantum tunnelling works and how it is responsible (among other things) for the alpha decay. Inside a nucleon, there are two quarks with the same charge, so they will repel ...
26 views

### Piezo transducer face movement

I have an ultrasonic piezo transducer that I am running with a 60Vpp signal. The material is probably PZT or similar. Can anyone supply a ballpark figure for the likely peak to peak mechanical ...
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### Would it be possible to “recycle” nuclear warheads into nuclear energy? [closed]

The number of nuclear warheads in the world is estimated (!) to be over 16,000. [0] Surely, this stockpile represents a massive threat to humanity. My question is simple. Can we repurpose these ...
A rod of length $l$ and mass $m$ has $ml^2/12$ as moment of inertia about an axis through its center of mass. Say now we take four identical copies of the rod above and form a square frame, whose ...