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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Relative motion in particle measurements

I was thinking about measurement of particles at almost-zero energies/temperatures and the movement associated with it. Compared to an observer next to the particle who sees the particle moving at ...
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43 views

How would I know if I were a 1 mm tall robot? [closed]

In the 1955 science fiction short story, The Tunnel under the World (SPOILER ALERT) a chemical plant explosion kills all the inhabitants of a town, whose consciousnesses are then uploaded into ...
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124 views

Meaning and logic of Einstein's train thought experiment

This seems to be a recurrent topic but I wasn't able to find any satisfactory discussion about this tought experiment. I will quote the original story from Einstein's and put my doubts inside: Up ...
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1answer
64 views

Why does the 'sticky bead argument' for (gravitational waves carrying energy) work?

Throughout much of the 20th century there was debate about whether Gravitational Waves were real, and whether or not they carrier energy and could be detected. It is often presented that Feynman's ...
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39 views

Where does an object with density lower than outer space go?

Assume there was an object with lower density than that of the interstellar medium (which is extremely low already at just a few particles per cubic meter). If that object were released on Earth, ...
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5answers
114 views

Airplane on a treadmill - Variant Thought Experiment

This thought experiment is in a way related to the (in)famous airplane on a treadmill problem. If you take a ball and place it on a treadmill, will the ball: Move backwards relative to the ground ...
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105 views

Do gravitational waves travelling through a medium produce sound?

Say Alice decided to orbit dangerously close to a couple of black holes circling each other. She is in a heavily enclosed astronaut suit, as is Bob, who is floating much further away. Assuming Alice ...
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71 views

A thought experiment about Heisenberg's Uncertainty Principle

If there is a box full of magnetized particles which are taking random movement continuously, then I put a coil connected to a device that can detect the value of current in it and it's designed to ...
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Is this thought experiment violating the the Second Law of Thermodynamics?

There is an adiabatic box, with a board in the middle, which is adiabatic too.The board separates the box into two parts and there is a small hole in it, which is close to a coil and the hole has a ...
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Do gravitational vawes deplete energy even if there's nothing they can affect?

I've read multiple times that one of consequences of gravitational waves being a thing is, that they make any orbit unstable. As long as the two or bodies orbit around each other, they create ...
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29 views

Is there a limit in dimension?

According to wikipedia Dimension In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any ...
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60 views

Einstein's relativity of simultaneity train/embankment thought experiment

Einstein's thought experiment I'm referring to is this one: http://www.bartleby.com/173/9.html briefly: train/embankment experiment is where lightning strikes at either ends of the running train ...
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41 views

The photon clock thought experiment

In reference to this video. If a photon clock moves away from us the photon will travel greater distance and therefore the clock will tick slower, so I would assume it will tick slower if it is ...
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2answers
143 views

How does the Physics work for the Quantum Suicide thought experiment?

On page 5 of this paper written by Max Tegmark, Tegmark discusses a thought experiment called 'Quantum Suicide'. As far as I understand it, this experiment was created to show the experimental ...
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61 views

Graviton detector thought experiment

I was recently thinking of a thought experiment: Assumptions Graviton detectors can exist The equivalence principle will hold in the final theory of quantum gravity We can accelerate the graviton ...
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23 views

Force impact when lifting objects traveling at a relative velocity of 0

During a break my colleagues and I came up with the following Gedankenexperiment I would appreciate if you guys helped us find the solution for: Truck (weight 5t) traveling at 80 kph with a ...
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1answer
83 views

Apparent paradox concerning Heisenberg's uncertainty principle

I have just begun my Introduction to Quantum Mechanics course in my undergrad and I am trying to understand the uncertainty principle on a fundamental level. I think the best way to understand the ...
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1answer
96 views

Thought experiments about $c$ [closed]

Poincare had a brilliant thought experiment about what if everything in the universe doubled in size, would anybody notice any difference or even be able to measure anything that can be compared with ...
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2answers
129 views

Classical physics in curved space

I'm trying to learn General Relativity. As a stepping-stone between classic (Newtonian) physics and complete relativity, imagine a universe where space is curved, but time is perfectly flat. Also, the ...
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17 views

Do we have the potential technology to harness the energy the Earth is constantly giving us? [duplicate]

Messing around with fun physics, and it got me thinking. I probably am not the only or the first one to think of it. I am wondering what more experienced physicists on this site can contribute to this ...
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129 views

How can a photon “stop”? What does its world line look like? [duplicate]

Einstein famously made a thought experiment: what would he see if he sat on a beam of light? His answer was -- it's impossible. Owing to him being a body with mass, he can never ever reach light speed ...
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2answers
50 views

How is Q superposition in Q information different from a classical dice?

Let's consider a dice with 1 or -1 on its faces, opposites faces adding up to 0. The point of this post is to relate the quantum coherence of a single qubit to something "weird", i.e., incapable of ...
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1answer
18 views

Gliders in a trailer

Everybody has heard I the old thought expirement of the birds in the trailer where the man hits the trailer the birds take flight and the trailer gets lighter. This has been disproven by the ...
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3answers
321 views

Are Newton's laws followed in non-inertial frame of references having all their objects and observer moving with same acceleration?

Consider a hypothetical scenario. In our universe there are two merry-go-rounds 1 and 2 and a distant planet. There is no other object having mass. There is a robot X on the planet. There are two ...
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254 views

Can something (again) ever fall through the event horizon?

Since I am more confused by the answers given in this site to the many variants and duplicates of this question, with some arguing that from the point of view of the falling observer, it happens in ...
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2answers
108 views

Thought experiment on light accumulation

Consider an object which is a spherical one-way mirror, and let's call it the "Sphere". For the needs of the thought experiment, suppose that: the Sphere is perfectly spherical the mirror is ...
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1answer
93 views

What's Wrong With This Quantum Analogy?

"Sometimes the idea of the quantum is compared to the units we use for money. A dollar can be divided into smaller units, where the cent is the smallest possible unit." A question I came ...
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486 views

Casimir effect for spinning Casimir plates

I recently thought of the following experiment. Let's say I have two plates in vacuum facing each other. Now, due to the Casimir effect, there will be some internal attraction between the plates. Now ...
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Conservation of momentum in Heisenberg's microscope

In working through Heisenberg's microscope, conservation of momentum for the photon and electron tells us that \begin{align} \frac{h}{\lambda}=\frac{h}{\lambda'}\sin\theta+p_x\,, \end{align} where ...
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353 views

Pendulum moving faster than speed of light

In classical mechanics, the period $T$ of a pendulum is given by $$ T = 2\pi\sqrt{\frac{l}{g}},$$ where $g$ is the gravitational field and $l$ the length of the rope attaching the bob to the pivot. ...
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111 views

Must we test whether e.g. $A=B$ and $A=C$ implies $B=C$ by experiment?

Chaper 10, conservation of momentum in "The Feynman Lectures on Physics" in the chapter entitled, the authors write that Suppose we know from the foregoing experiment that two pieces of matter, ...
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Can a mouse rotating a wheel violate conservation of angular momentum?

I have been thinking on the following problem. Part I. Imagine we have a mouse enclosed in a rigid box. We placed the box on a frictionless surface (ice might be a good example). Can the box start ...
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1answer
441 views

Feynman Lectures: Why a non-reversible weight lifting machine cannot lift higher that a reversible one?

Consider weight-lifting machines—machines which have the property that they lift one weight by lowering another. Let us also make a hypothesis: that there is no such thing as perpetual motion ...
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Taking selfies while falling, would you be able to notice a horizon before hitting a singularity?

I am generally interested in the role of "pings"(0a) between participants (a.k.a. "signal roundtrips"(0b), as familiar for instance from Synge's "five point curvature detector") in the determination ...
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Limits on the information obtained through optical measurements

Consider a Gedankenexperiment shown in the figure below. There are two lasers $S1$ and $S2$ with exactly the same specifications on paper. In practice, they are of course somewhat different but ...
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46 views

Pool full of Jell-O

Imagine I have filled my backyard swimming pool (8 feet deep) with a solid block of Jell-O. What would happen if I tried to swim in it? My understanding is that the viscosity of the "water" doesn't ...
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631 views

Black Body Golf Balls

The surface of a golf ball has about 35% more surface area (than a similar sphere) due to its dimples. So my question is simple, given identical radius, ideal black body material, and temperature: ...
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Is the Physics for extremely large and extremely small particles similar in any aspect? [closed]

Do the equations we use to describe natural phenomenon on a very large scale, work as well for describing natural phenomenon on an extremely small scale as well? Is there any correlation at all which ...
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is electromagnetic phenomena and particle behavior dependent on dark matter?

Dark matter permeates space and coalesce s in its own gravitational attraction. It neither absorbs or emits light or interacts well with baryonic matter. It deflects light on a path and is the sub ...
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2answers
50 views

Is this a possible monopole setup, or will it cancel out? [duplicate]

Suppose you have a ball that is covered in magnets, in which the North Pole of every magnet faces outward. Is this a monopole? Or at least "functions" as a monopole? And what will happen if you placed ...
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29 views

Simultaneous Decision/Motion

This is just a thought experiment I had and was wondering if any could give there input on it, Imagine we have to machines in the shape of a ball. When these machines are turned on, one machine will ...
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How did Lord Rayleigh find the volume fraction of argon to air?

In order to isolate for pure nitrogen, Lord Rayleigh and his colleagues took some air and removed oxygen, carbon dioxide, and water vapour, leaving behind what he believed to be pure nitrogen. In ...
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260 views

Special relativity mirror clock experiment inconsistency

Say I set up a relativistic mirror clock experiment in which a spaceship contains a set of mirrors with a photon bouncing between them. Say the photon's motion is parallel to the direction of motion ...
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2answers
326 views

Does the speed of light have a range of speeds due to medium-dependency?

An EM particle-wave propagates in a vacuum at a constant speed $c$, independent of the source/receiver but dependent on most mediums it moves through. Since the vacuum is a medium, and if logically ...
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197 views

Could gravity be repulsive at short distances?

I was wondering if it would be consistent with empirical data if gravity became extremely repulsive at short distances. For example (please bear with my use of classical formulas, I know little of ...
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275 views

How does potential energy work out for floating things?

Seeing a ship canal lift in TV spawned the following thought: "Oh my, this sure is a heavy ship and it can be lifted by simply adding water. What a marvellous machinery. After all, I could lift that ...
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3answers
413 views

What would happen to me if I was in the LHC while it was running? [duplicate]

This is possibly a stupid question, but one I have been always wondering. What would happen to me if I was in the center of the Large hadron Collider while it was running? Would the energy of the beam ...
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4answers
336 views

How would swimming in low gravity work?

Sorry I know very little of actual physics, I'm not looking for hard and fast numbers just a general idea of how the mechanics would work. For the sake of argument, say you were on a planet or moon ...
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65 views

What is the exhaustive set of experiments a quantum theory has to satisfy?

Any theory that is to explain the world correctly has to provide a mechanism by which the interesting results of quantum mechanics happen (e.g. diffraction patterns, momentum/position uncertainty, ...
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109 views

Relativity Paradox involving two charged particles

Suppose there are two charged particles separated by some distance $d$ both with an equal positive charge of $q$. The particles also have equal masses of $m$. $m$ and $q$ are chosen so the ...