A thought experiment is a hypothetical situation in which a hypothesis, theory, or principle is laid out for the purpose of thinking through its consequences.
Johann Witt-Hansen established that Hans Christian Ørsted was the first to use the German term Gedankenexperiment (lit. thought experiment) circa 1812. Ørsted was also the first to use the equivalent term Gedankenversuch in 1820.
Much later, Ernst Mach used the term Gedankenexperiment in a different way, to denote exclusively the imaginary conduct of a real experiment that would be subsequently performed as a real physical experiment by his students. Physical and mental experimentation could then be contrasted: Mach asked his students to provide him with explanations whenever the results from their subsequent, real, physical experiment differed from those of their prior, imaginary experiment.
The English term thought experiment was coined (as a calque) from Mach's Gedankenexperiment, and it first appeared in the 1897 English translation of one of Mach's papers. Prior to its emergence, the activity of posing hypothetical questions that employed subjunctive reasoning had existed for a very long time (for both scientists and philosophers). However, people had no way of categorizing it or speaking about it. This helps to explain the extremely wide and diverse range of the application of the term "thought experiment" once it had been introduced into English.
The common goal of a thought experiment is to explore the potential consequences of the principle in question:
"A thought experiment is a device with which one performs an intentional, structured process of intellectual deliberation in order to speculate, within a specifiable problem domain, about potential consequents (or antecedents) for a designated antecedent (or consequent)" (Yeates, 2004, p. 150).
Given the structure of the experiment, it may not be possible to perform it, and even if it could be performed, there need not be an intention to perform it.
Examples of thought experiments include Schrödinger's cat, illustrating quantum indeterminacy through the manipulation of a perfectly sealed environment and a tiny bit of radioactive substance, and Maxwell's demon, which attempts to demonstrate the ability of a hypothetical finite being to violate the 2nd law of thermodynamics.
I'm a 16 year old who has wondered this question for a while. If the multiverse theory is correct, and I understand correctly, there would be infinite universes in which each universe would be different from another in some form. If this is the case, would that mean that places and worlds that...
Imagine a plane 1 light minute across. Now imagine 1 person on either and of that plane. Between them, is a thin indestructible bar that is 1 light minute in length. In the center of this plane, a simple device has a wire that leads to a motion sensor on the left side of the bar. If the left...
Let us consider a hypothetical scenario, where we are able to translate any mass at a constant speed of 10m/s w.r.t to a given frame of reference. For simplicity, we are going to assume that the object is at rest initially.
Case 1 -
Now, consider 2 points A and B at a distance of 10m, and our...
Hello all,
I recently did a thought experiment and thought, "what if the universe as a whole is spinning?" This could solve the dark energy problem, as if the universe was spinning, there would be outward pull, and therefore keep the universe expanding. And, I don't know if this means anything...
suppose suddenly the sun disappears at a time t. at this arbitrary time t, the Earth should fling off tangentially to the point in its orbit at time t as there is no centripetal force keeping it in orbit.
we know light takes about 8 minutes to reach the earth.
so will humans on Earth experience...
The other day my friend asked me a really interesting question regarding the scene from interstellar where they go down to Miller's planet, where every hour on this planet is 7 years of Earth time. He asked me if they were to send a signal to the spaceship where Romilly was, what would happen...
If we’re looking through a telescope at a craft we launched from Earth that is now passing Mars and send a radio signal to our craft telling it to turn on one of its lights on and it takes thirteen minutes for the radio waves to get from Earth to our craft how long will it take before we see the...
I'm a former physics student and I've been thinking about an interesting problem that eventually led me to the following thought experiment that I'm having trouble resolving.
Imagine a two-compartment system, where one compartment is filled with He gas, and the other is filled with standard...
Thought experiment: single use of "magic"
Setup:
Let's assume we have a giant ball of water in space.
Magic: Let's assume the water does not compress its center under its own gravity. (Constant density of 1 g/cm^3)
Basic stuff:
The mass of this ball of water, (since it does not compress)...
Today, I had a thought experiment where I began to puzzle over inertia of very large masses being dropped.
Imagine a scenario where the Moon was suspended 100 m from the surface of the Earth alongside a marble at the same height. Now ignoring air resistance and the gravity exerted by the Moon...
A thought experiment about the speed of light. Say I build a 600,000 km long tube around the circumference of the Earth at the Equator. The tube's inner diameter is constant at 54.4505 mm. A snooker ball is perfectly manufactured to its lowest tolerance by a special new machine. Each one is...
Hi, Physics Forum!
I've been wondering what would happen in the following thought experiment. I am not physicist and may have made some incorrect assumptions. Please explain if any of these assumptions are wrong.
What would happen if you threw a piece of (very long and strong) rope into a...
I met with a little conflict between Pauli and Einstein? Can you please help. Its a thought experiment.
Consider a single crystal which is 1km long. During its formation, due to Pauli’s exclusion principle, no two electron will have same quantum state. Now consider two electron, one with E and...
Hello all, I have a question that's been bothering me the last few days and wasn't sure where to turn.
Recall the original Special Relativity thought experiment: A spaceship travels at constant velocity v, moving in the positive x direction. An observer on the spaceship emits a photon directly...
Hello all,
I'm starting to learn the math in physics and have the following thought experiment I want to use to work through something I own.
The setup: There is a wall 10m from the center of a 1m diameter sphere. There is a 1m diameter light source casting a 1m diameter shadow on the wall...
Hi everyone,
Recently I randomly thought of a thought experiment of something going faster than light, along the lines of a shadow or some other "non-information carrying object". In this case it would be an empty seat.
The idea is to take 800 million and one chairs of half a meter breadth...
Einstein's relativity of simultaneity & quantum measurement paradox.
Suppose a rocket traveling close to the velocity of light which emits a single photon from its midpoint at point A, illustrated below. The rocket is equipped with a single detector drawn in green at the front of the rocket...
Hi everyone,
I've been working on developing a crypto-currency called eQualityCoin for a while now and hoped someone here might be able to help me "classify" the system in a formal mathematical sense.
The system's main feature is a simple rule for how it determines a purchaser's exchange...
I decided to perform a little thought experiment -- without the mathematics.
Assume we have two Schrodingers' Cats. After a while, they will be in a superposition of being alive and dead at the same time. Now assume that they are entangled, and we open the boxes at the exact same time.
Cases...
This is a thought experiment I came up with this evening. It must surely have been considered before but I couldn't find any reference and I've come up with it independently.
NASA has positioned a clock in Earth's thermosphere that can be viewed from outer space with a powerful enough telescope...
Hello.
I want to share a thought experiment that could tell Quantum Mechanics apart from Pilot-Wave interpretation. It goes like this:
Quantum Mechanics vs. Pilot-Wave:
Quantum Mechanics: Waves collapse to particles. Waves disappear when particles are detected.
Pilot-Wave: Waves are real but...
Okay so to start, this is just about the most random inapplicable proposal ever, so bear with me. Its just a cool question to consider. So, here goes: What would happen, (again, this is highly theoretical) in the instance that an enormous screen - much like the ones that rests behind most...
Ok, so as far as I understand it, it is impossible to turn linear momentum (p) into rotational momentum (L), but I don't quite understand why. The main thought experiment I have in my head is this:
A ball in space is traveling with a momentum mbVb, and gravity and friction are assumed to be...
Just a thought:
The momentum quantum number given for s states is l = 0. If an S state electron dropped in energy, and emitted a photon with l = 1, what would take place?
Am I correct that the electron could only drop to a lower l = 0 (an S state) orbital?
Pretend we have a multi-slitted grating whose slits are infinitesimally small. We On each slit is a detector. If we shine (UPDATE) light monochromatic light through the grating, what distribution pattern occurs on the screen past the grating?
I understand the train of thought to a slight...
I had a little thought experiment, in which there are two objects with the same masses near each other (same height) on freefall. If I set up a point that is on an instant besides the two masses and call it the center of torque, I get that the torque produced by the nearest one's weight is...
Obviously we don't have the technology to make this work now but I would like to know how plausible this is as a concept/thought experiment. Basically the idea is to discover a gas or liquid with a very high activation energy (for some reaction) so that it can absorb an explosion or control a...
Homework Statement
"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. How is this analogy incorrect?
Homework Equations
E=nhf
The Attempt at a Solution
My thought is that...
I was contemplating the size and shape of the universe. Our observable universe is perfectly 3D spherical, but that's a result of a finite speed of light and a beginning of time, and I was wondering if there was a way to deduce the size of the universe. I imagined the universe as a 4D sphere...
I have been pondering black holes for some time and have had trouble with the problems presented simply because there is very little we can do to study the phenomena. I have always thought of a black from the outside looking in, or basically the only way we can hope to see a black hole. However...
I'm curious about time dilation sizes of below 4 situations. Please assume I'm observing the situations far away in zero gravity. And please ignore all SR effects, just focus on GR.
http://dishdev.me/data/timedilationq.png [Broken]
Equivalence Principle says acceleration and gravitational...