Paradox Definition and 1000 Threads

A paradox is a logically self-contradictory statement or a statement that runs contrary to one's expectation. It is a statement that, despite apparently valid reasoning from true premises, leads to a seemingly self-contradictory or a logically unacceptable conclusion. A paradox usually involves contradictory-yet-interrelated elements that exist simultaneously and persist over time.In logic, many paradoxes exist which are known to be invalid arguments, but which are nevertheless valuable in promoting critical thinking, while other paradoxes have revealed errors in definitions which were assumed to be rigorous, and have caused axioms of mathematics and logic to be re-examined. One example is Russell's paradox, which questions whether a "list of all lists that do not contain themselves" would include itself, and showed that attempts to found set theory on the identification of sets with properties or predicates were flawed. Others, such as Curry's paradox, cannot be easily resolved by making foundational changes in a logical system.Examples outside logic include the ship of Theseus from philosophy, a paradox which questions whether a ship repaired over time by replacing each and all of its wooden parts, one at a time, would remain the same ship. Paradoxes can also take the form of images or other media. For example, M.C. Escher featured perspective-based paradoxes in many of his drawings, with walls that are regarded as floors from other points of view, and staircases that appear to climb endlessly.In common usage, the word "paradox" often refers to statements that are ironic or unexpected, such as "the paradox that standing is more tiring than walking".

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  1. B

    Logic: How is this question different from the Omnipotence paradox?

    We're all too familiar with the version of the Omnipotence paradox, the so-called paradox of the stone : Can God create a rock so heavy that even he cannot lift it? ... (1) ... which has been discussed ad nauseam in philosophy classes and on the web. Now, how about this version: Can...
  2. Nabeshin

    Do train gaps appear smaller in motion?

    A friend of mine posed this SR paradox to me a few weeks ago and I was unable to come up with a convincing answer (nor have I been convinced by any I've heard!). The problem is as follows: Assume we have a train track which has certain gaps in it. At rest, the train which moves on the track is...
  3. T

    Time Paradox: Exploring the Relativity of Motion

    First of all, hello forum. I'm new. :biggrin: Alright, so I was recently informed of two things. I'm no physics student, but nonetheless I was still interested in these things. 1. The speed of light is always constant for all observers. 2. To compensate for the paradox of a light particle...
  4. L

    Twin Paradox in a Flat Toroidal Universe: Time Dilation and Inertial Frames

    In four dimensions, a flat torus is an object that has zero curvature but still has closed geodesic curves. What this means is that if you try to measure geometry locally, you will find that it is perfectly Euclidean. Nevertheless, if you travel on a straight line, you'll eventually end up...
  5. T

    Exploring Time & Movement: A Paradox of Dimensions

    Why do we call them 3 dimensions when all that they are, are just the ability of movement in space? Physical movement cannot be restrained in any vector. It takes place in a 3 dimensional dimension. Thus 1 dimension is physical movement in space and the second dimension is time. Within the 1st...
  6. S

    Exploring the Twin Paradox: Searching for the Oldest Frame of Reference

    I was just working on my knowledge of the twin paradox, and had a question that I couldn't find an answer to anywhere: If I understand it correctly the paradox is resolved because the two frames are not symmetrical, one is non-inertial, so that frame has it's clock run slower. So if you carry...
  7. A

    Olbers Paradox and The Sherwood Forest

    1. Homework Statement Suppose that in sherwood forest, the average radius of a tree is equal to R= 1m and the average number of trees per unit area sigma = 0.005 m^-2 . If Robin Hood shoots an arrow in a random direction , how far , on average, will it travel before it strikes a tree? 2...
  8. A

    Light Sphere Paradox: A Conundrum with No Solution?

    Hi The setup for this conundrum is like the light sphere illustration. Two frames F and F' ------- F' moving ---->+x at v=.8c At the point of colocation of the origens: x=0 and x'=0 t=0,, t'=0 a light burst is emitted . Looking at two points at...
  9. L

    Paradox with Newton's E=1/2mv2 ? Looking for clarification

    paradox with Newton's E=1/2mv2 ? Looking for clarification... I don't understand why these points of view don't balance. This is non-relativistic. If two objects are traveling towards each other from opposite walls of a room, then the sum of their Kinetic energies relative to the room does...
  10. Shackleford

    Is this a paradox in Special Relativity?

    We covered SR last semester in Modern Physics I and also covered early Quantum Theory and started Modern Quantum Theory. I've been speculating a bit on SR recently since I started reading The Universe and Dr. Einstein a guy at work gave me. If we have the Earth as a stationary reference frame...
  11. T

    Fletcher's Paradox - Lynds' Resolution or not?

    Hi there. I was wondering recently about the Fletcher's Paradox, and Peter Lynds' solution - the idea that time can't truly be measured in individual instants. Now, I'm not actually a physicist - just a science fiction writer. But has anyone proposed the alternate solution that motion is an...
  12. DARKSYDE

    Angular momentum and the twin paradox

    If you were spinning on a marry-go-round approaching the speed of light, would you experience time dialation?
  13. B

    Exploring the Twin Paradox: 4 Solutions = 0?

    how about this: silly idea, but think about it: the square root of 1 = {+1,-1} and we all know: t'=t/(1-(v/c)^1/2) in essance, t' must simultaneously have values of {+t',-t'} for all velocities not equal to zero and approaching c. this means that for a relativistic frame of...
  14. Z

    Is Changing to Polar Coordinates Always Valid for Double Integrals?

    An integral paradox ?? let be \int_{0}^{\infty}xdx \int_{0}^{\infty}ydy changing to polar coordinates we get that the double integral above shoudl be 2\int_{0}^{\infty}r^{3}dr althoguh they are all divergent , is this true can we ALWAYS make a change of variable to polar...
  15. M

    A paradox about Maupertuis' principle (symplectic viewpoint)

    Maupertuis' principle states in symplectic formulation that the integral of the tautological 1-form is extremal among its integrals on other phase space curves on the given level set of the Hamiltonian, connecting the same starting end ending fiber. Specifically, for closed phase trajectories...
  16. N

    Latest on black hole infromation paradox?

    WHat is the present status about the black hole information paradox? Is there some consensus? Could someone recommend good recent papers discussing the current views? Thanks! Patrick
  17. Jonnyb42

    Twin Paradox (by acceleration)

    Ok so, supposedly you have two twins in [seperate] spaceships, one approaches the speed of light going away from his twin, then decelerates until going the same high speed but opposite direction, decelerates again to stop next to his twin buddy. The twin that did not move (relative to the very...
  18. Z

    Rotation of coordinate system mistake or paradox?

    Hello to all, I am currently studying computer graphics and I have came up with the following problem. Consider that we have three coordinate systems, let's say CSA1, CSA2 and CSA3 that have the same origin and differ by a rotation. That is to CSA2 connects to CSA1 by R12 and CSA3 to CSA1 by...
  19. A

    Feynman's Paradox: Solving the Mystery of the Rotating Disk | Solution Revealed

    hi folks, this is my first post..and here i would like to present a solution to a paradox posed by feynman in the 2nd volume of his lectures (17-4)...for those of you who wish to see the problem here's the link http://varatek.com/scott/feynman_problems.html it's the last problem in that page...
  20. A

    Solving the Twin Paradox with Lorentz Transformation

    We use the following formulas for the Lorentztransformation: x’ = [ x / sqrt(1-v**2/c**2)] - [vt / sqrt(1-v**2/c**2)] (1) and t’ = - [ (vx)/c**2 / sqrt(1-v**2/c**2)] + [ t / sqrt(1-v**2/c**2)] (2) The twin paradox reads as follows. Gea and Stella are identical twins. Stella...
  21. R

    Twin paradox and length contraction

    We know that the twin paradox is not a paradox since one of the twins accelerate and time passes more slowly for him relative to his twin on earth. My question is why can't we apply the same reasoning for length contraction? If one of the twin A measures the lengths of sticks in the reference...
  22. D

    Is action at a distance possible as envisaged by the EPR Paradox.

    Is action at a distance possible as envisaged by the EPR Paradox?
  23. I

    Solving the Twin Paradox: Age Difference Between Bill and Ben

    Homework Statement Two twins, Bill and Ben are 30.0 years old and they leave Earth for a distant planet 12.0 light years away. The twins depart at the same time on Earth, and travel in different space ships. Bill travels at 0.93c, while Ben travels at 0.70c. What is the difference between...
  24. T

    Time dilation & symmetrical twin paradox variant

    I'm still trying to understand time dilation, the twin paradox, and the effect of acceleration. Yes, I've read the twin paradox FAQ, but it only gets me so far. Here's a hypo I came up with. I've tried to simplify it by (a) making the observers symmetrical and (b) eliminating the...
  25. G

    Twin paradox thought experiment

    I've been wracking my brain for days trying to comprehend everything that deals with the twin paradox. I have a vague understanding of relativity and its effects, but am massively confused by most of the explanations given on this forum and other places. I think perhaps it extends from my lack...
  26. M

    How Long Will It Take for All the Rope to Fall Off the Table?

    Thanks to the post by studiot, I can update my discussion with the calculations. Here's the problem: "Suppose that a flexible 4-ft rope starts with 3 ft of its length arranged in a heap right at the edge of a high horizontal table, with the remaining foot hanging (at rest) off the table...
  27. P

    Relative speed of light paradox

    I'm no physicist, but I read that the speed of light is constant from all observers (regardless of relative speed) and in doing a thought experiment I encountered a problem. Here is the situation: John shoots a laser at you. You turn and run away at near the speed of light, but you look back to...
  28. M

    Wigners Friend where is the paradox?

    So i try and try to understand why physics should suggest a quantum entanglement of wigner friend and the observed system, because instantaneous measurement makes a collapse in the system, there should be no question when the wave function is determined. Suppose we consider two equations...
  29. K

    Relativity paradox in exponentially accelerating train

    Using Einstein's train thought experiment, suppose a train is accellerating exponetially so that the engine remains forever ahead of a beam of light without it ever reaching the speed of light. V = c[ 1 - e^(-t)] for the train The light would approach the engine but never quite reach it...
  30. M

    How can dual 4-space modelling provide insight into Wigner's Friend Paradox?

    Homework Statement The conjecture implies the eigenstate of the observer and observed given by alpha and beta. The problem i am reaching at the end, is whether the well-known Wigners Friend Paradox is answerable by describing the observer and the observed, and then a second observer in terms...
  31. M

    Paradox of the Universe - Physics or Voodoo Philosophy?

    I wrote a response in a thread entitled "What is the single most important thing for life to exist in the universe?" . I thought about it some more and I am wondering if this paradox is scientifically sound or is it just crazy philosophers taking physics and making into voodoo science. I hope...
  32. J

    Understanding the Twin Paradox: Exploring the Effects of Relativity on Aging

    I'm kind of a noob who's posted a question or two here before to settle arguments and such. Please don't kill me if this has been covered before. I was reading some stuff about space travel trying to get some creative ideas for a sci/fi book idea I had. Nothing serious and really nothing to...
  33. S

    Exploring the Paradox of Time and Light Speed

    I'm really confused! How can time be relative and speed of light absolute? If you were moving a long with speed, whilst someone else was stationary would you not measure light to be slower??
  34. E

    Twin paradox without length contraction

    Hi all, apologies if this has been posted a million times before... I'm trying to explain the twin paradox without getting involved with length contraction. One way to think of it is Twin A remains at rest on Earth then twin B goes off at 4c/5 to Alpha centauri 4 light years away, then...
  35. G

    Proving the One Way Twin Paradox: O' Reads T'>0, K Clock Reads More than T

    In the following, "G" stands for "gamma". Clocks O and O' coincide when they mutually read zero. POV is that of K'. Prove: When O' reads T'>0, the coincident K clock reads more than T'. Proof: When O' reads T', O reads T'/G and O' coincides with K clock at x=GvT'. That clock reads...
  36. J

    Twin Paradox: Anne & Joe's 20th Birthday

    Homework Statement Anne and Joe are twins, happily living in an inertial frame. On their 20th birthday Joe decides to take a rocket. (a) According to Anne the rocket moves with constant speed v = \frac{3c}{5}. For 6 months it moves away from Earth and then returns in time for Anne's 21st...
  37. N

    A paradox about Drift Velocity

    Hi! I was just reading about drift speed and I read that the speed is about 10^-4m/s. It then struck me that if electricity is carried by electrons, then in a given circuit, how is the light bulb lighting up so quickly when according to my calculations the time taken to travel 0.5 metres for...
  38. B

    Exploring the Paradox of Time and Light Travel

    If time stops at the speed of light, how does light travel throught space and time? Example: The light from a star 12 light years away travels throught space and takes 12 years to get to earth. But in those 12 years the time on the star has stoped. Same goes for the light that is leaving...
  39. B

    How do heat production and rolling resistance work together?

    Hi "If you cycle up a hill and then back down with no net change in elevation, it seems as if your slower uphill speed and faster downhill speed should offset each other. But they don't. Your average speed is less than it would have been had you cycled the same distance on a level road...
  40. D

    Twin paradox in a closed universe

    I`ve thought about a special sort of twin paradox. I know the usual explanation of the twin paradox but give me please the answer to this special case: Imagine: A static universe (non-expanding) with a closed geometry and a circumference of one lightyear. The twins start their journey in...
  41. M

    Twin paradox - which twin is older?

    Hi everybody! :) can anyone help me with this idea: in the twin paradox, a twin that travels at speed of light in space should be younger than the one that remains on earth. But why can it be other way? Can we say that the twin on the Earth is traveling at speed of light compared to the twin in...
  42. B

    Twin Paradox - Acceleration vs Velocity

    Sorry, I know there are tons of threads about this, but I've been though them all and couldn't answer this satisfactorily myself. You know how it goes. You have 2 twins, A and B, who are magically the same age exactly. They start at the same point in space, each in their own spaceship. They...
  43. N

    Twin paradox and Hafele-Keating experiment

    In a few places I have read things along the line of this: I am getting confused, because some people say this experiment has resolved the paradox and some people think its still a paradox. How exactly has the twin paradox "been verified experimentally" from the HK experiment?
  44. G

    Is gravity the key to solving the twin paradox in general relativity?

    If the fixed stars/galaxies did not exist, would there be a twin paradox?
  45. M

    Is Time Slower or Faster Inside a Moving Train?

    Dear forum, when I first read about special relativity I came up with this paradox. I went to the teacher who gave me the booklet but he couldn't answer my question. I'm quite confident that this forum is the place to answer my question: Does time goes slower or faster inside the...
  46. Loren Booda

    Is special relativity sufficient to treat the twin paradox?

    I cannot conceive of a complete path which the "away" twin can follow, relative to the "home" twin, that does not involve significant acceleration. A straight line from home to star then back home in reverse, a centrifugal circle from home (0 degrees) to star (180 degrees) to home (360...
  47. edpell

    Unraveling the Twin Paradox: Three Inertia Frames in a Race Against Time

    In this story we will have three inertia frames. Frame Fi where both twins start together and at rest with respect to each other. Frame FL moving at a speed v in the negative x direction and Frame FR moving at a speed v in the positive x direction. Both twins zero their watches and start...
  48. Jonnyb42

    Relativity and time (twin paradox)

    I have thought about it and I have found to be confused about something, regarding the twin paradox. As I know it, the twin paradox (set up to emphasize my confusion) is as follows: Two spaceships floating in space pointing away from each other, let's say A and B. When B accelerates and...
  49. J

    Another paradox from the force transformation laws?

    Hi all, I've been recently digging into SR in my attempts to better understand electromagnetics. One thing that has been giving me trouble is the force transformation laws, which seem to give rise to some pretty gnarly paradoxes, one of which I've listed here: Consider two objects, where...
  50. T

    Why Does the Traveling Twin's Clock Show Less Time in the Twin Paradox?

    Hi, I can see that this topic has been much discussed, but I haven't seen a thread on it with the particular spin I want to give it (just the journey out from Earth). I understand the traditional view of the twin paradox (I think!): Two twins a and b are on Earth and each has a clock. The...
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