Paradox Definition and 1000 Threads

If I could route a signal from here-and-now to an event in my past light cone, then clearly I could make an irresolvable causal paradox by having the arriving signal disable the button that sends it, so I'll choose to believe that I can't send messages back in time TO HERE. Now I've heard it...

Has anyone analysed the LIGO merger detection http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 in the context of the BH information paradox? Is there any evidence that the gravitational waves carried any information that could compensate for the change in areas of the initial...

From my limited reading I get the impression that the bouncing black holes proposed by Rovelli and Vidotto implies a solution to the information paradox. The information comes back out when the bounce happens. But how does this relate to the idea of complimentarity? It seems the latter was the...

I'm getting quite stuck on this problem here. Galileo said that Xb = Xa - V*Ta. (This follows from dv = dx/t --> Xa - Xb = t*dv --> the above formula) Thus, it is concluded Xa = Xb + V*Ta, but why? In my thought experiment the objects are moving relative to each other, thus if A is moving away...

Hello. Thank you to everyone who helped me with my previous post where I had general questions on special relativity. Several users suggested that I start by trying to understand the relativity of simultaneity which I did. Although I haven't mastered it, I understand it better now. Also, someone...

Hi, I found this 'paradox' which supposedly says that SR is incorrect, I have a hunch why it may be a flawed argument, but can't personally get the numbers right. Perhaps it's a fun exercise for some of you to destroy the argument. Here it is: So my hunch why this is incorrect:

Consider the diagram below (sorry for the quality:frown:). The circle is the front view of a cylindrical iron rotor (highly ferromagnetic, very low reluctance). The orange part is a single turn of a conductor (very high reluctance) wound around the rotor body. The grey lines are magnetic field...

I refer to a Schwarzschild Black Hole as the simplest example, and a well defined time outside the hole, say the Schwarzschild time. The information paradox of BH deals with the question of what stuff has fallen into the hole, but I am not aware that it deals with the question when the...

The puzzle presented below is derived as a variation of the Blue-eye paradox" which has been discussed in the following thread. https://www.physicsforums.com/threads/blue-eye-paradox.875870 THE PUZZLE Teams of N people each are each given the following challenge. The rules for the challenge...

Hi, I'm trying to understand the twin paradox and time dilation. Someone told me that if observer A and observer B are traveling apart from each other with each having a uniform speed of .4c they will have the same age when they return back at the point of origin. Even though I'm unsure of...

I've seen Elitzur's brief presentations on this. Two excited atoms pointed at a detector. The detector goes off, it isn't known which particle fired the photon, so you interrogate one, it gives a definite answer but violates bell's inequality? I'm sorry but I'm lost at such a vague...

What is the firewall paradox?? is it possible in a black hole or in its event horizon ??

I understand that the twin paradox isn't truly a paradox, and that the traveling twin ages since the universe can be "aware" of his traveling. However, my question is how does the time dilation formula break down? Why can't you integrate dT' = dT * Gamma for each velocity as the traveler...

Forgive my naivete, but I've struggled with the twin paradox for a long time. If there is no privileged frame of reference, why does time dilation apply only to the traveling twin? I have been told (possibly erroneously) that the stay-at-home represents the entire universe, but this seems to...

It seems to me that Gibbs' Paradox (that the entropy of a classical ideal gas, calculated by phase-space volume, is not extensive) can be resolved without assuming that particles are indistinguishable. Suppose instead the opposite: that particles are distinguishable, meaning that each one can...

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...

micromass submitted a new PF Insights post Some Misconceptions on Indefinite Integrals Continue reading the Original PF Insights Post.

A bag contains two balls. Either ball can be black or white. Without drawing any balls, determine the colors of the balls.Solution The bag could contain any of three contents, each with probabiity \tfrac{1}{3}. . . \boxed{B B} \qquad \boxed{BW} \qquad \boxed{WW} Add a black ball to the bag...

I set up a Twin Paradox scenario and accompanying spacetime diagram to help better understand the resolution, but I had a question about the diagram I was hoping someone here could help answer. Please excuse the hastily drawn diagram! (Note: the ' frame corresponds to the outbound trip, the...

The blue-eye puzzle (or paradox, or riddle) is a well known logical puzzle, explained and discussed in many places, including http://puzzling.stackexchange.com/questions/236/in-the-100-blue-eyes-problem-why-is-the-oracle-necessary https://en.wikipedia.org/wiki/Common_knowledge_%28logic%29...

I heard recently that Dr. Maldecena recently commented to Dr. Susskind, regarding the black hole information paradox, that ER = EPR. Can anyone illuminate this for us mere mortals? It seems to link all information via non-locality, which has interesting implications.

Can anyone recommend a good (peer reviewed) reference that discusses low Reynolds number flow around a cylinder? I'm specifically looking for derivations of the drag coefficient. The usual 'gold standard' references...

It would be really appreciated if somebody could clarify something for me: I know that stationary states are states of definite energy. But are all states of definite energy also stationary state? This question occurred to me when I considered the free particle(plane wave, not a Gaussian...

The so-called Simpson's Paradox arises frequently in medicine, economics, decision sciences, demography and many policy fields. Have there been any instances of it in physics (or chemistry)? Perhaps the most newsworthy instance of the paradox was in connection with possible gender bias in...

Greetings: I am attempting to prove that no set contains all sets without Russell's paradox. What I have thus far is this: Let S be an arbitrary set and suppose S contains S. If X is in S for some X not=S, then S - S cannot be empty. But this is a contradiction; hence if S contains S, then...

I decided to work a bit on my Java program created to visualize the Twin Paradox. It shows two diagrams. One from the perspective of the stay at home/earth twin on the left side and the traveling twin on the right side/diagram. The accelerations are considered to be near instantaneous, hence why...

I know this has come up before but there is still something puzzling me about the whole BB paradox. This is the problem phrased in the context of our evolving universe. As far we can tell the universe will expand forever ( assuming dark energy is not something variable but is a constant). In a...

I just read an article (linked below) today and found it to be quite curious and interesting. In short, physicists have taken Schrödinger's cat paradox to a whole new level by adding a second box. I’m still very new to all the ideas of quantum physics, but apparently this addition of another box...

The night is dark and full of SPOILERS...... Okay, so in the last Game of Thrones episode, a massive twist involving what appears to me to be a bootstrap paradox occurred. I was wondering what anyone who saw thought about it and for those who did or didn't whether or not it makes sense. The only...

Hi, I have some questions about the video about the Banach-Tarski Paradox from the YouTube channel Vsauce: 10:09: Is this really a valid way of constructing the hyperwebster? In this order, one will never get past sequences of only "A". Shouldn't one follow an order like A, ... ,Z, AA, ... ...

Homework Statement How does the blackbody paradox argument show that the electromagnetic field cannot be classical while electrons and atoms are quantum mechanical? Should the same arguments apply to treating gravity classically and electrons quantum mechanically? Homework Equations The...

Hi guys, So If any of you aren't familiar with the Fermi Paradox, I highly advise you read about it. It is easily one of the most interesting topics I've come across. IF you can't be bothered for this I have included a small summary of what the Fermi Paradox in my survey (see below). I'm doing...

A rubber ball is bouncing on a flat surface. Every time it bounces, it loses energy, while the sound of the ball hitting the surface accelerates (because the intervals of the ball impacting the surface become shorter with each bounce). The ball seems to be accelerating when, in fact, it is...

When a collider such as the lhc accelerates two protons side by side, would thy seem to gain mass and then distort st? And if so, would the lab frame see them attract each other? How would the attraction be explained from the perspective of each particle, if they don't see the other particle...

A bit over two years ago, Chris Adami et al. published their solution to the firewall paradox (referred to without source in http://msutoday.msu.edu/news/2014/plugging-the-hole-in-hawkings-black-hole-theory-1/, perhaps referring to http://arxiv.org/abs/1310.7914). But what has happened in the...

I was thinking about a gendanken experiment that I don't know how to solve: Imagine we tie one extrem of a rope in the Earth and the other one in the Sun, with some tension, and connected to a dynamometer (obviously in ideal conditions: no heat, no rotation etc.). My question is: when will the...

Homework Statement In the book "In searcg of life in the Universe" A.D. Ursula gave the following formula R1/C1 = R2/C2 (A) when the contact between two civilizations happens, where R - result from a contact and C - cost to make a contact for those civilizations. Homework Equations The key...

Here is a linear version of the Ehrenfest paradox with the goal of understanding the observations of someone in motion in the scenario, then solicit your views on whether the calculations are correct and whether one can extend it to circular motion.Consider a one dimensional train of proper...

Thinking and reading about the twin paradox recently, I encounter a lot of explanations and resolutions that don't make sense to me. At its most basic, the issue is- when two bodies are in different frames of reference, why shouldn't relativistic effects affect both equally, negating time...

So say that there are twins. Twin A is near a heavy planet and twin B is out far away in space. Why does time slow for twin A compared to B? Can't they say that they both are in inertial frames because there are no forces(gravity isn't a force) acting upon them? Therefore for each of them can...

To quote from this wikipedia article: How is this resolved? It seems a little bit nonsensical but I do get the logic. This has me very confused...

If the torsion of the straight line is undefined what happens with the information about the torsion? It is known (https://en.wikipedia.org/wiki/Quantum_no-deleting_theorem, http://van.physics.illinois.edu/qa/listing.php?id=24045) that the information conserved in a system can be nor created...

Hi. From an outside observer's view, any object approaching the event horizon of a black hole appears to slow down and never quite pass through the horizon. So information about those objects can always be retrieved (if you correct for the redshift). So what actually is the information paradox...

Hi, I just saw a video about the twin paradox, explained by using GR. I was wondering whether I understood the video correctly. The video states that when the rocket twin is first accelerating away from earth, his clock and his Earth twin's clock are different, but, roughly the same because of...

If you had twin 1 on the earth, and twin 2 fly to a star and back at a speed of v with the Earth and star separated by a distance L, twin 1 sends out flashes at intervals of t seconds (measured in his frame). Taking into consideration the numbers of redshifted and blueshifted flashes that the...

I've never understood this: we measure the edge of the observable universe to be around 13 billion LY away, so we are seeing the state of things 13 billion years ago. But 13 billion years ago, wasn't the universe much, much smaller? Did distant quasars and galaxies look like they do "now" so...

In Information Theory, entropy is defined as the unpredictability of information content and, as such, the entropy of the output from so-called pseudo random number generators (PRNG) is often measured as a test of their "randomness". An interesting paradox arises with this definition... Start...

According to the EPR-paradox, if we have a pair of two entangled spin-1/2 fermions A and B and measure z-component of A, B collapses immediately as well(i'm using these letters for both particles and their observers). The 'canonical' solution is then to state that it is not possible to transfer...

I just came across this video today with Brian Greene talking about how time slows down for an observer near a black hole relative to an observer who is farther away. See the first two minutes: It reminded me of another video I saw recently by David Butler where he states that the twin...

Hi All; I was trying to understand Lorentz Transformation equation and special theory of relativity, but as I compared the derivation with a thought experiment which I imagined I found the whole Lorentz Transformation Equation fails. The details of the problem is given below. I know I m wrong...