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Questions tagged [thought-experiment]

Hypothetical situation in which, for simplification, only some physical aspects are considered in order to further understand or reveal contradictions between the laws governing them.

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Areas with anti-parallel gravity in classical physics

I cannot indicate an error in the following reasoning if it is done in the framework of classical physics. Let's make the imaginary setup with two wedges and the ball, when the gravity in the left ...
Artem's user avatar
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2 votes
0 answers
67 views

Understanding topological censorship: is something wrong with this example?

Earlier today I was discussing with someone about the possibility of space (not spacetime) being a torus, and how this is different from a sphere. For simplicity, let us assume spacetime is of the ...
Níckolas Alves's user avatar
1 vote
1 answer
65 views

Marble as soft as a mattress

I read this in the book The Dark Forest by Cixin Liu. On page 121, With his body, he felt the hardness of the ore and, weirdly, thought of a problem put forth by his high school physics teacher: How ...
Felix Martinsson's user avatar
-3 votes
1 answer
185 views

Somewhat silly special relativity and cosmology thought experiment [closed]

Edit: I have already tried to delete this several times. I have already posted that I would delete this if I could and it was deleted. I have three very legitimate masters degrees in physics and more ...
Steven Dorsher's user avatar
2 votes
6 answers
501 views

Fundamental principles for simple radiative heat transfer problems

The picture below illustrates what is intended to be a very simple one-dimensional textbook-style radiative heat transfer problem. It is meant to be a pedagogical tool for explaining the greenhouse ...
looksquirrel101's user avatar
0 votes
2 answers
107 views

General relativity, Mach's principle and rotation

During the Gravity Probe B press conference, Kip Thorne gave the following statement: Suppose that the entire universe were rotating rigidly instead of being non-rotating [...]. How would we know? ...
WordP's user avatar
  • 365
2 votes
2 answers
107 views

What is the mechanism by which objects feel the electrostatic force?

This is more of a conceptual question than a mathematical one, but you may answer however you wish. Suppose we imagine a universe with a single proton in it, then magically create an electron one ...
ING's user avatar
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9 votes
5 answers
2k views

A bar that appears straight in one reference frame appears bent in another?

Is there a relativistic effect at play that explains the following thought experiment, that I am unaware of? The apparatus depicted in the image has two straight bars in the middle emitting light from ...
Joona's user avatar
  • 93
2 votes
4 answers
110 views

A thought experiment regarding special relativity [duplicate]

I am currently delving into the intricacies of Einstein's theory of relativity and striving to grasp its fundamental essence and implications. Your assistance would be greatly appreciated. Here's my ...
Kyriakos's user avatar
0 votes
1 answer
66 views

Is there an experimental set up that would produce a "macroscopic" a weak or strong nuclear force fields?

I was wondering if there is an experimental set up that would produce something equivalent to a classical electromagnetic field for the weak and strong nuclear forces. I know that the those forces are ...
Bryan D's user avatar
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1 vote
3 answers
95 views

Rigorous definition of convective heat transfer

Through all textbooks I've come across, convective heat transfer is traditionally defined along the line of "[...] a process by which heat is transferred by movement of a heated fluid such as air ...
student_of_heat's user avatar
0 votes
1 answer
114 views

From Faraday's Paradox to the design of a One Piece Axial Flux Motor

My question is introduced through the following picture: In the thought experiment a) a Faraday copper Disc with a magnetic field attached to it (out of page) is rotated clockwise. A Lorenz force ...
C Marius's user avatar
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0 votes
1 answer
168 views

Linear version of Faraday Paradox: different results in different inertial frames [closed]

Setup: Consider the following setup: A copper plate is fixed in a uniform constant paralel magnetic field. The whole setup is moved to the right with the uniform velocity $\vec{v}$. You may assume ...
C Marius's user avatar
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2 votes
1 answer
150 views

Modification of The Faraday Unipolar Generator Setup for Propulsion

I am wondering if the following device produces a forward thrust. Setup explanation The North (red) and South (blue) poles of a permanent magnet are fixed to the cart as well as the copper spokes (...
C Marius's user avatar
  • 365
7 votes
4 answers
2k views

How can the weight of a container be affected by an object's buoyancy?

Suppose a table tennis ball is immersed in a fluid and held down by a string. The container is placed on a scales. What will happen to the reading of the scales if the string breaks? How can you ...
Yitian Chen's user avatar
0 votes
2 answers
251 views

Special relativity - what is the age of my twin after a one-way trip? [duplicate]

I have a twin who stays on Earth, and I will move to another planet 4 ly away. I will travel at a certain relativistic speed towards this planet. What I just described here is the first half of the ...
Mr Deevid's user avatar
-6 votes
1 answer
52 views

Thought experiment of 0 times infinity and dimensions [closed]

Take a cube at 1x1x1 and cut it in half. Take the 0.5x1x1 and cut it in half again. Eventually, you get an object that is 0x1x1. The object does not disappear. It instead now exists in the 2D world. ...
No Name's user avatar
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0 votes
1 answer
34 views

Would it be possible for a cylindrical magnet suspended vertically down from a hanging magnet to levitate in static equilibrium?

Let's assume that a cylindrical magnet is clamped by an horizontal arm extending out of the wall. The top of the magnet is its north pole and the smooth face facing down is its south pole. If I bring ...
ARJ's user avatar
  • 15
-1 votes
1 answer
73 views

Thought experiment about special relativity [duplicate]

Hypothetical scenario: Observers A and B exist The way A experiences time is the baseline B is moving at a speed such that for it, time passes 2x as slow as the baseline(i.e. 2 year for A is 1 year ...
NE0bject _'s user avatar
-1 votes
1 answer
72 views

The train-and-platform VS Causality and Simultaneity

for long time I was ruminating on the train and platform experiment and “what if” extension of this experiment… So, what if the light striking on either end triggers system (one on each end) with ...
david's user avatar
  • 19
2 votes
2 answers
118 views

Relativity on a massive bridge

Suppose there is a ridiculously large bridge, fixed at either end (light seconds long at least). The bridge is constantly under the influence of gravity. If the ends are severed simultaneously, the ...
Tiger's user avatar
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0 votes
1 answer
136 views

What is the actual version (using electrons) of this quantum thought-experiment from an MIT lecture?

In the first lecture of the MIT quantum-mechanics 2013 course, the professor develops basic abstract concepts, by inventing hypothetical binary measurable properties of electrons (hardness (H)= hard ...
Terminality's user avatar
2 votes
3 answers
215 views

Is it possible, and if so how should we remodel thought experiments in classical SR in the context of the Scharnhorst Effect?

I was thinking of the following thought experiment which is related to the ideas user David Elm asked here Suppose you have a pair of photon mirror clocks as is often used in SR, where one of the ...
Sidharth Ghoshal's user avatar
1 vote
1 answer
91 views

Confusion about asymmetry of time dilation and space contraction in a special relativity thought experiment

So I've been trying a fairly simple thought experiment and I'm not able to wrap my head around an aspect of special relativity. Here is how it goes: A train is moving at steady relavisitic velocity V ...
rep_movsd's user avatar
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0 votes
1 answer
106 views

A possible way to generate Electric current

What is electric current? An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of ...
D13G's user avatar
  • 33
1 vote
2 answers
215 views

Penrose's explanation of the two-slit experiment

I don't understand what Penrose is talking about in the following paragraph of his book "The Road To Reality". I have read about the two-slit experiment in other texts and I understand it (...
moshtaba's user avatar
  • 1,409
0 votes
1 answer
60 views

What happens when screen is not placed where Image is focused but elsewhere?

When we try to form a real image on a screen by a convex lens, we place the screen at a distance where the image is focused. But if we try to place the screen at a distance less than the distance ...
Garv Chaudha's user avatar
1 vote
3 answers
400 views

The double slit experiment and classical mechanics

As I understand, it is perfectly possible to explain the standard double slit experiment with a laser beam using only classical physics. On the other hand, this experiment is one of those experiments ...
THC's user avatar
  • 355
0 votes
1 answer
94 views

Does a measurement violate conservation law? [duplicate]

(Edited according to the discussion with @naturallyInconsistent. The edited part is highlighted in italic.) We have an experimental bench and we assign a coordinate system $(x,y)$ to it. We shall call ...
Leo's user avatar
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3 votes
0 answers
64 views

What if you ejected a cone of material from the Earth out into space?

For calculation purposes, let's say it's a cone with cone angle (at Earth's center) of 30 degrees, that extends down to the outer surface of Earth's solid inner core, and the entire mass is ejected ...
Rabadash8820's user avatar
0 votes
1 answer
60 views

Quantum measurement in a strong magnetic field

I have a thought experiment that has been puzzling me regarding a spin-$\frac12$ particle placed in an extremely powerful magnetic field (say 1000 T for the sake of hyperbole) directed along the ...
slithy_tove's user avatar
0 votes
3 answers
83 views

Thought experiment with specific heat

I have been thinking about the following thought experiment regarding a material whose specific heat decreases with external electric field (see this article for an example of such a material). Say ...
slithy_tove's user avatar
0 votes
2 answers
80 views

Work principle of Heisenberg Uncertainty Principle

Let us assume that one quantum particle is moving in some space (phase space). I appoint two observers to observe that particle. Now at any instant of time I ask the $1^{st}$ observer to measure the ...
M Sagnik .'s user avatar
5 votes
1 answer
361 views

Stuck on thought experiment about light [duplicate]

Say we have a very long fluid pipe with the width of a few astronomical units, and that this pipe is perfectly resistant to sustain the stress of a perfectly incompressible fluid going through it ...
Ícaro Lorran's user avatar
1 vote
1 answer
157 views

A tower with—apparently—different average weights depending on the inside activity

The apparent paradox involves a tower with internally pumped water that appears to have different average weights depending on the pumping configuration. Since the system is closed, we expect the ...
moonblink's user avatar
  • 947
0 votes
1 answer
58 views

A thought experiment on escape velocity [closed]

Note: air resistance will be ignored for this thought experiment. Suppose you hold a ball in your hands and have some kind of magical mechanism that allows you to begin accelerating upwards at a ...
ING's user avatar
  • 69
1 vote
2 answers
64 views

Simultaneity in Special Relativity (conflicting times in thought experiment)

I'm learning Simultaneous Events in Special Relativity. Lets say I have a light emitter in the center of the train; it shoots photons horizontally to each end of the train. The train moves with ...
ludicrous's user avatar
  • 149
3 votes
3 answers
144 views

Length contraction from a contracted frame of reference (thought experiment)

Consider the following situation: You are moving with high speed on a road on earth and are looking at the night sky, in particular at two stars. In the rest frame of earth, you and your eye are ...
Phlipp's user avatar
  • 31
0 votes
1 answer
469 views

Why does an object become invisible if its index of refraction is equal to the index of refraction of the medium that contains it?

If we suppose that we can change the refractive index of an object to be equal to the refractive index of its surrounding so that it becomes invisible, how can we explain this process?
Jordan G's user avatar
1 vote
0 answers
40 views

If all radioisotopes in the human body decayed at once?

Let's suppose that - in the quantum randomness of nuclear decay - the Carbon-14 and Potassium-40 atoms inside an adult human were to all undergo decay at once, or within an extremely short amount of ...
Searinox Navras's user avatar
0 votes
1 answer
152 views

Why can't we say that the information is travelling faster than light? [duplicate]

Let's imagine the following thought experiment, Two particles, A and B are entangled on the Earth. As decided, Alice (a friend of Bob) stays on the Earth with the A and Bob travels with the B to a ...
Sazzad Hissain Khan's user avatar
0 votes
1 answer
72 views

Alternative thought experiment of Special relativity

The first picture setup is used a lot in explaining special relativity. According to the reference frame of the red person in the left space craft, the light emmited from the light source will travel ...
Mohamed Mostafa's user avatar
4 votes
8 answers
2k views

If you were encased in an iron block and dropped from a building, what would happen? [closed]

Imagine that you are inside a box made of iron. You are surrounded by iron and there is no gap between you and the iron. Assume you can breathe (but it doesn't matter). I said iron but it could be any ...
No Signals's user avatar
0 votes
1 answer
78 views

Minimum time passed for stationary observer at destination in relativistic physics

While my friend and I were discussing about relativistic physics, we came up with the following question. Suppose a person $P$ wanted to travel from point $A$ to point $B$ in one-dimensional space. ...
Prajith Velicheti's user avatar
0 votes
2 answers
99 views

Could gravity be used to cool down matter?

Thermal energy being the movements of particles, could we have a system that could use gravity to reduce the thermal energy of particles? For example, if we imagine: A box containing Argon in its ...
Adrian B.'s user avatar
  • 101
1 vote
3 answers
372 views

If a clock is moved along a crooked path half as fast, and thus for twice as long, is the total time lost by the clock due to time dilation halved?

There is a type of relativity thought experiment where, in order to eliminate the problems caused by signal delay due to the finite speed of light, a lattice of clocks and rods (either automated or ...
Matthew Christopher Bartsh's user avatar
3 votes
2 answers
218 views

Why does Norton's thought experiment require a specific dome shape?

Norton's dome famously shows that Newtonian mechanics (as a mathematical model) is non-deterministic. To do this, a very specific potential is chosen. But why does this not work with any dome shape, e....
Matt's user avatar
  • 33
1 vote
4 answers
275 views

Does it take light longer to reach me if I'm moving away?

I'm having trouble grasping the intuitions behind the second postulate of special relativity, particularly what it implies. For example, imagine that a laser pointer is aimed at me at 1 lightsecond ...
joshua mason's user avatar
-1 votes
2 answers
106 views

Does anything "break" in physics if you allow for instant (faster-than-light) communication?

Assume that two entities, Alice and Bob, can communicate thoughts literally instantly. If Bob thinks "Alice, I want you to jump", then Alice (many, many light-years away) will know that ...
chausies's user avatar
  • 1,090
-2 votes
3 answers
156 views

Can you resolve this special relativity paradox?

I've devised a thought experiment called the "Killer Crate Paradox" to further improve my understanding of Lorentz Transformations. This is not a paradox I am able to resolve, so please read ...
γ Anon's user avatar

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