Paradox Definition and 1000 Threads

I am trying to understanding magnetism and I've been running into this thought problem A particle a in a magnetic field B responds with Force F=|q|v x B. frame S: The field is B1, caused by a moving charge/s - current at speed v. the particle is at rest, F=0. frame S' moves with speed v/2...

Hi all, (See attached image file) Two mutually coherent and collimated light beams intersect as shown, creating the stationary 'bright' and 'dark' fringes of fig.A. Suppose that, after the fringe pattern has formed, we insert a very thin (compared to the fringe-width) and (ideally) perfectly...

I have a random paradox I seem to have found with three colliding observers, though to explain it properly I'm going to use a bit of visual aid and a bit of abstracting it from the math (or setting the math so that it works according to my example). For anyone who wants the TLDR, read this...

Hello everyone, Reminder: The key of the explanation of the "twin paradox" resides in the acceleration. We know that the time runs slower for the twin in the spaceship (since it was accelerated)...

Homework Statement In the twins paradox, suppose that Florence begins at rest beside Methuselah, then accelerates in Methuselah’s x-direction with an acceleration a equal to one Earth gravity, “1g”, for a time ##T_F/4## as measured by her, then accelerates in the −x-direction at 1g for a time...

Consider two bodies A &B are moving apart with a velocity V due to the expansion of space. According to an observer in A the body B is moving away and an observer in B feels the body A is moving apart. Can some one answer in which body the time dilates and why?. ( I am specifying once again that...

Dear All, I am doing the Special Relativity course at World Science U, and came across this question which I got wrong: When 100 nanoseconds have elapsed on traveling Gracie's watch, she immediately stops, turns around, and heads back toward George at the same speed of her outbound journey...

I was reading the wikipedia page on the twin paradox (https://en.m.wikipedia.org/wiki/Twin_paradox). It says: The mechanism for the advancing of the stay-at-home twin's clock is gravitational time dilation. When an observer finds that inertially moving objects are being accelerated with...

First, I will give my understanding of Bohr's resolution using an example that Bohr considers in his discussion. Then I will quote a passage where Bohr summarizes his resolution of the paradox. Finally, I will try to respond to John Bell's comments on this resolution. I would be interested in...

I thought of yet another simultaneity paradox that I find even more confusing: We're just in space with spaceships. There's a ship moving past us at some relativistic speed. On the front and back of the ship there are thrusters at the top that can be activated by a pulse of laser light striking...

When Bell says that the thread in put under "intolerable stress" and breaks, what happens then? Suppose that instead of the thread there is a light rod, which breaks at the point of attachment to the back spacecraft , so it is left sticking out backwards from the front spacecraft .. In the...

The Rich Investor’s Paradox Let us assume you have been given an immense amount of money and you are worth $50 billion. In addition you have a clairvoyant that can read tomorrow’s edition of the Wall Street Journal. You decide to start investing in stock because you believe you have a sure...

There is a similar thought experiment I imagined to help me begin to understand the Bell's spaceship paradox: Consider two positively charged spheres, placed side-by-side inside a frame S' with a string stretched to the point where it balances the repulsive electrostatic force between them. For...

This was straying from the point in the original thread, but I thought it made a point... The stay-at -home twin is at rest in her frame and her clock must therefore measure proper time. The traveling twin, carries his clock with him; it is therefore at rest in his frame and must also measure...

Hi, I am reading the biography "Einstein's greatest mistake" from David Bodanis. On page 39 the author explains some of the consequences of relativity by referring to (although he doesn't mention it by name) the twin paradox. He explains that someone accelerating at high speed away from Earth...

First off, let me just say I love this forum and all the people in it! The world is a better place because of all of you who take the time to post here and I thank you all! The most popular explanation to resolve the twin paradox seems to be the asymmetry that arises because the ship...

Homework Statement Find electrostatic potential of a solid sphere with reference point of 0 statvolt at infinite. Homework EquationsThe Attempt at a Solution Potential energy of a solid sphere is ##\dfrac35 \dfrac{Q^2}{r}##. And I know ##\displaystyle U = {1\over 2} \int \rho \phi dv##. So...

Imagine a spatial frame of reference attached to a point-like particle. It has x=0 since it is at the origin and p=0 since it is at rest. Having definite position and momentum is normally considered a violation of the uncertainty principle. How would you resolve this paradox? 1. Position frames...

I have a reversible chemical reaction described by the balanced equation: ##aA+bB=cC+dD##. I devise a reversible process to take a closed system containing these species (and its surroundings) from thermodynamic equilibrium state 1 to thermodynamic equilibrium state 2: State 1: a moles of...

trilobite submitted a new PF Insights post Exploring the Spectral Paradox Continue reading the Original PF Insights Post.

Su, Francis, et. al. have a short description of the paradox here: https://www.math.hmc.edu/funfacts/ffiles/20001.6-8.shtmlI used that link because it concisely sets forth the paradox both in the basic setting but also given the version where the two envelopes contain ( \,\$2^k, \$2^{k+1}) \...

I'm reading the paper of the EPR paradox and I'm confused in the meaning of this: "The elements of the physical reality cannot be determined by a priori philosophical considerations, but must be found by an appeal to results of experiments and measurements......when the operators corresponding...

I read in a popular science magazine in the UK that "recent" observations of the universe indicate that the number of galaxies in the the universe is actually so vast that Olbers paradox is still a paradox. The short article postulated that they had solved the paradox by proving that light from...

Jim al Khalili did a (basic level) TV programme in the UK last night where he featured a smartphone app which works as a space-time "odometer". Now you can experiment on your own version of the legendary brain-teaser with your friends, no need to go to Alpha Centauri and back! Go for a walk...

I have always been fascinated with black holes and information paradox. If quantum bits made up spacetime. Could the information getting inside a black hole be possibility encoded in its quantum bits? Look at https://www.quantamagazine.org/20150428-how-quantum-pairs-stitch-space-time/

I don't know much about general relativity, but I'm curious if Zeno somehow foresaw the reallty of the universe many many years before Einstein did(without any rigour ofc, but still the idea holds?). Understanding the Zeno's arrow paradox, stating that an arrow is motionless at a certain moment...

Case 1) Two rockets (no Earth involved) have an exactly the same acceleration profile/flight-plan during round trip but they dispatched to opposite directions. At the start both rockets are docked to the same space station...both rockets have an identical engine operation plan during the round...

How can light be a constant for any observer? I understand how it fits into equations and what not, but how can it be a constant. If I throw a baseball forward at 10m/s in a train going 40m/s. I perceive it as 10, an observer on the ground would perceive it as 50. Why doesn't the same apply to...

Hello! I am trying to work out the various cases for the potential step problem in the context of the Klein Gordon equation. I was wondering if one must consider the situation where E<mc^2 when working out the situation of E-mc^2 <V< E+mc^2 where V is the value of the potential after the step...

Imagine that we have two metal rods, and both measure 1 meter, a measurement done from the same inertial system when they are at speed = 0. These two rods are equal, the extreme points of the first one are called a and b and its inertial system is called F, the extreme points of the other rod...

Let me begin by saying I know I'm doing something wrong here, but I'm having trouble seeing what it is. This is a reformulation of https://www.physicsforums.com/threads/plugging-eom-into-lagrangian.905099/, where I've reduced the issue to a much simpler problem. Moderators, feel free to close...

Sets which doesn't contain themselves are called normal sets while sets that contain themselves are called abnormal. Let ##N## be a set of all normal sets. Prove that ##N## is normal if and only if ##N## is abnormal. Proof. ##~~\rightarrow ~~ ## Suppose ##N## is normal such that ##N \not\in N##...

Hey! I am going to do a presentation about the bootstrap paradox in a few weeks and I need some help. I understand what the bootstrap paradox is but I need some help to sum up the theory so that i becomes easy (or at least easier) to understand. If you have any examples or facts that's fun...

I am not a physicist but interested in the decade long debate between Einstein and Niels Bohr, especially in the philosophical implication of the EPR Effect. I've been wondering if anyone could explain why Einstein, Podolsky and Rosen didn't applied the Lorentz Transformation formula - the...

I have learned that ΔG is the amount of available energy. So to understand it i used a simmple body system rather than chemical reaction,which is the sliding of a block on a fixed wedge(height h and inclination angleθ). 1)my system is ball -earth and rest surrounding both in thermal eqilibrium...

Has anyone heard of "Bauer's Paradox" in Einstein's working out his equations for General Relativity? The description I came across was extremely fuzzy (something about an expression for a certain tensor adding up to be zero when it shouldn't, or vice-versa), so I am looking for a better...

I'm sure that there are limits to the analogy between the event horizon of black holes and the "Rindler horizon" for an accelerated observer, but there are a number of similarities: For Schwarzschild spacetime as described in Schwarzschild coordinates: Spacetime is static, and a rocket must...

Hi. Trying to solve the Gibbs paradox for two identical volumes of ideal gas with ##N## particles each, I found the mixing entropy to be $$\Delta S=2N \log(2)-\log((2N)!)+2\log(N!)\enspace .$$ The usual approach now uses Stirling's approximation to the order ##\log (n!)\approx n\log (n)-n##...

Wikipedia has this interesting article about a physics "paradox" that Einstein came up with: https://en.wikipedia.org/wiki/Tachyonic_antitelephone It shows that if you were able to send a signal faster than the speed of light, then you could send a message back in time leading to a causality...

I am not sure I understand exactly what was the situation was with the EPR paradox Example: for simplicity: two electrons are coupled. One with spin up and the other with spin down. Since they are coupled there are one state. Separate the electrons one in one galaxy and the other in another...

Hello there, Suppose there are two inertial frames of reference ##S## and ##S'## with coordinates ##(x,ct)## and ##(x',ct')## such that ##S'## is moving relative to ##S## with velocity ##v##. Suppose ##v>0##, that implies ##\gamma >1##. We know that a Lorentz boost is given by: $$ x' = \gamma...

There is a solenoid on top of a disk with charges attached to it. and there is a clockwise current through the solenoid. So by disconnecting the battery, the current will lower, and hence the flux of the magnetic field though the disk will lower, and according to faraday's law, there will be...

There is something about the twin paradox in special relativity that has always bothered me. One twin sets out on a journey at a large fraction of the speed of light, turns around and returns. The fact that the returning twin is the one who is younger is explained by the fact that they are the...

Twins leave Earth in opposite directions, accelerate at the same rate until their relative v = ~c, hold this v for 20 years (or however long), then decelerate at the same rate to v=0, and accelerate at the same rate back towards Earth until their relative v again =~c, hold for same amount of...

Hi, A cat cannot be alive and dead at the same time. Is it possible for particles in a nucleus to be both protons and neutrons at the same time? How could you tell whether this is happening?

If we have a frictionless hollow tube and a ball which just fits into it. All the surfaces are frictionless. Now if we put in the ball about at the center of tube and rotate the tube about one of its ends with a constant angular velocity ,then the ball swoops out of the other end . If we see...

good evening everybody! i'm studying these days the nuclear activity and this amazing world where an atom try to find its/her stability ! so i came across the famous radiations but then stopped by something i didn't quite understand! when an atom release a beta radiation a negative one for...

"The Fermi paradox or Fermi's paradox, named after physicist Enrico Fermi, is the apparent contradiction between the lack of evidence and high probability estimates, e.g. those given by the Drake equation, for the existence of extraterrestrial civilizations". I have always failed to understand...

We have got some SR work to do, however we have only had 1 introductory lecture. I have a problem with one of the problems. Question: A rod of 1m parrallel to the x-axis, travels at un-relativistic speeds at 45 degrees. It passes through a slit - also parallel to the x-axis - that is 1.1 meters...

I thought of this 'paradox' which is somewhat similar to the twin paradox but can't be explained by a lack of symmetry etc. It is very similar to many paradoxes I have heard before of which the resolution is known (which is why I am mostly sure this can be resolved) Bob is looking through his...