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. N

    What is the Real Life Twin Paradox?

    Landed on this PBS page, and read that there is going to be a real life twin paradox. Excerpt from the article "Astronaut twins Scott and Mark Kelly are about to realize this experiment: when Scott returns from a year in orbit in 2016 he will be about 28 microseconds younger than Mark, who is...
  2. nuclearhead

    Can you answer this virtual photon paradox?

    In order to get my head around virtual particles I've created the following question. Maybe some bright person can answer this. If I can answer this question I feel I would have the required understanding to explain virtual particles to other people. In the diagram below, A is a radioactive...
  3. D

    Twin Paradox in Kerr Metric - Help Needed

    Hi. I've been struggling with a formulation of the twin paradox in the Kerr metric. Imagine there are two twins at some radius in a Kerr metric. One performs equatorial circular motion whilst the other performs polar circular motion. They separate from one another and the parameters of the...
  4. G

    How to Solve the Twin Paradox Problem Using Lorentz Transformations

    Homework Statement This is a typical twin paradox problem as laid out in Griffith's Introduction to Electrodynamics, problem 12.16. The problem states that, on their 21st birthday, one of two twins - we'll call her Alice - departs Earth for star X at (4/5)c. Upon arriving at star X, she...
  5. Vinay080

    Why can't a particle ever reach a non-terminating decimal form radian value?

    Consider a particle P moving in a circle of radius r as shown in the figure. Premise 1: Position of the particle can be described by the angle θ. Premise 2: Particle reaches the position with an angle θ if it has covered the angle lesser than θ. Premise 3: Particle can never reach...
  6. ShayanJ

    Information paradox, dismissed?

    One of the important problems in modern physics is BH information paradox, which is the problem with non-unitarity of Hawking radiation. But now there is this paper which says that this process is actually unitary and so BH information paradox is, not solved, but dismissed. I'm posting this...
  7. Vinay080

    Is the Length of an Arc Equal to its Straight Line Distance?

    Premise 1: Line is composed of points. Premise 2: Each point is associated with specific co-ordinates (x,y). Premise 3: Lines of equal length have equal number of points. Lines of greater length have greater number of points. Premise 4: Each value of x in the function f(x) gives a single...
  8. PeterDonis

    Using General Relativity to analyze the twin paradox

    In a previous thread, reference was made to an entertaining "defense" of relativity by Einstein, which can be found here: https://en.wikisource.org/wiki/Dialog_about_Objections_against_the_Theory_of_Relativity One of the arguments Einstein makes in this dialog is that the twin paradox can be...
  9. B

    Olbers' paradox and infinite number of stars

    Olbers' paradox reckons that the sky should be blazing bright if there is an infinite number of evenly distributed stars (galaxies). the argument is something like in every direction that you look there would be a star. so the sky would be blazing bright. but even if there were an infinite...
  10. 1977ub

    Clocks Within Each Ship in Bell Spaceship Paradox

    I believe length contraction always makes more sense when integrated with reminders of relativity of Simultaneity. Let's say the engines are at the back end of each rocket. For the viewer "A" in the initial frame, they begin moving and continue accelerating simultaneously, and clocks next to...
  11. I

    Wave/Particle duality in Blackhole paradox?

    Alrighty, this is my second attempt at this thread, as my first was removed due to speculating theories so i will try to keep this short and clear. Is it possible to apply the concept of Wave/Particle duality to explain the event horizon paradox in which a particle can cross the horizon in a...
  12. Rectifier

    Proving "-1 = 1" Wrong: Ideas?

    Hey there! These is this falsidical paradox that I can't seem to prove wrong. ## -1 = (-1)^1 = (-1)^\frac{1}{1}= (-1)^\frac{2}{2} = (-1)^{\frac{2}{1} \cdot \frac{1}{2}} = (-1)^{2 \cdot \frac{1}{2}} = ((-1)^2)^{\frac{1}{2}} = (-1)^{2 \cdot \frac{1}{2}} = ((-1)^2)^{\frac{1}{2}} =...
  13. J

    Electric dipole equivalence principle paradox?

    Imagine an electric dipole with charges ##+q##, ##-q##, mass ##m## and size ##d##. Assume this dipole is oriented horizontally and is sitting at rest on top of some weighing scales on earth. As the charges are at rest the weight of the dipole is just ##-mg##. But by the principle of...
  14. Q

    Unraveling the Fermi Paradox: Exploring the Mystery of Extraterrestrial Life

    What exactly is a Fermi Paradox, I am having trouble grasping this idea. Can you please keep it in simple language?
  15. L

    Special Relativity: Twin Paradox Question

    I've already completed most of the question, it's an add on at the end that has stumped me. I've calculated using time dilation the difference in ages between the two twins, Joe traveled at v = 24/25 (c=1 units) to a planet for 7 years in HIS reference frame and returned at v = 12/25 The...
  16. J

    Falling charged objects paradox?

    I have been thinking about a simple thought experiment in classical electromagnetism that seems to disobey conservation of energy. I'd be very interested to hear where people think I'm going wrong. Imagine that we have two oppositely charged objects with charges +q, -q and masses m. Assume...
  17. W

    Resolving Ehrenfest Paradox: STR vs General Theory

    Can the ehrenfest paradox be resolved using STR or does one require to go in general theory? If it can be, please recommend a book or online source which explains it from the basics. Also I'm somewhat unclear on what exactly the paradox is,does it state that- Since the ratio of it's...
  18. B

    I Simply Cannot Understand Olbers' Paradox -- Finite/Infinite Universe

    My astrophysics lecturer did Olbers' paradox today in class, and while discussing it, it seemed as if she actually believes that the universe is infinite (infinite amount of space and infinite amount of matter). I came and questioned her about this afterwards, and when I said I had always...
  19. Palpatine

    Help Applying SR to Calculate Time Dilation

    I made this pic to illustrate my problem. A spaceship (labeled B) departs from a space station (labeled A) at 80% the speed of light (0.8c). A applies the time dilation principle and calculates that B's clocks are running slower than his. Some time later a smaller craft (labeled C) detaches...
  20. S

    The Twins Paradox: Understanding the Slow-Motion Effect

    I've read different reasons for the reciprocal illusion experienced by the twins (the slow-motion effect). I've not been able to understand the reason that the traveling twin would see the earthbound twin moving in slo-mo. Can anyone offer a simple explanation -- or is there actually no...
  21. ubergewehr273

    Paradox on the Chandrasekhar Limit

    The Chandrasekhar Limit is defined as the maximum mass of a white dwarf which is said to be 1.44 solar masses. My doubt here is if it is defined as being the mass of 1.44 suns then the sun should not even be burning fuel right now. Only then will its mass remain the same. The Sun keeps burning...
  22. D

    The Paradox of Aging in Relativity: Resolving the Twin Paradox with a Twist

    Hi all,I know the twin paradox has been discussed many times, so I hope you'll bear with me. My version has a slight twist. Suppose twin's A and B start off in a "rest" frame in dead space, frame F, at x = 0. At t = 0, A moves in the direction x with velocity c/2, and B moves in direction -x...
  23. ShayanJ

    What is the solution to the 1=0 paradox involving self-adjoint operators?

    I know this is raised several times in this forum but I still don't see what's the solution! So I want to discuss it again. Consider two self-adjoint operators A and B which obey [A,B]=c I. Now I take the normalized state |a\rangle such that A|a\rangle=a |a\rangle . Now I can write...
  24. A

    What is the solution to the straw paradox?

    1.The problem I have been facing is understanding how a straw exactly works ?? I know the general, conventional solution given to this problem by the principle of working of a barometer, but I think it has a serious loophole. 3.They say as a vacuum space is created in the straw due to our...
  25. Gravity

    Does Penrose's Andromeda paradox prove determinism?

    Article: https://en.wikipedia.org/wiki/Rietdijk–Putnam_argument
  26. K

    A Language Spin: The Paradox of Zero Multiplication and Social Perception

    If Anna has 0 coins and Bertus has 0 coins aswell. Can you say that Anna has twice as much coins as Bertus? Because 2*0=0. But couldn`t you also say that Anna has four times more coins than Bertus, but simultaneously Bertus has 5 times more coins than Anna? Making it a paradox?
  27. DiracPool

    Twin paradox and the size of the universe

    Ok, let's take the standard twin paradox, Alice leaves on a trip in her rocketship near the speed the light, and comes back to Earth some time later to find herself 5 years younger than her twin, Bob. Now they go out to lunch and strike up a conversation as to how old the universe is. Alice...
  28. C

    Where Does the Traveling Twin Lose Time in the Twin Paradox?

    Some thoughts about the twin paradox (with a new question/paradox at the end): Beginners, like myself, when confronting the twin paradox often want to know where it is that the traveling twin loses so much time. A frustrated poster trying to explain the paradox posted this: He's been given...
  29. F

    Does the Twin Paradox Still Apply with Identical Acceleration Readings?

    I am surprised this has apparently not been discussed here as such in this forum (nor anywhere else on the web). The point is that in the classical space-ship twin paradox, not only the traveling twin will be subject to a proper acceleration, but, according to Einstein's equivalence principle...
  30. S

    Solving the Spring-Weight Paradox: 0.039m

    Homework Statement Homework Equations Fs = -kx w = mg The Attempt at a Solution I said that when the spring is stretched out at its max, the weight pulling down will equal the force of the spring pulling up. Fs=w -kx = mg -(1500)(x) = (3)(-9.81) x = 0.01962 m The solution key tells me...
  31. AdityaDev

    Exploring the Time Travel Paradox: What Happens When You Meet Your Future Self?

    I was thinking about time travel...this is what i came up with ----> lets say person A (age 20,year 2014) travel to the year 2024 and meets himself (A2, age 30).lets say a kills his future A (i.e A2) and travels back in time (which i know is not possible but then). Now A is back in 2014.After 10...
  32. J

    Explaining the Paradox of Measuring Photons from the Sun

    Imagine a stream of photons moving from the sun to the Earth (A, B, C, D, E, F, G, etc.). Now imagine 2 different men measuring the speed of the photons, and (somehow) recording which photon is hitting them. They are in the same position, but one is traveling 1/2 the speed of light (relative...
  33. D

    Could the Twin Paradox in GR be Generalized to Completely Empty Space?

    Whenever the twin paradox in GR seems to be discussed, it always seems to be done in the presence of a large mass such that the twins can be considered as test particles moving in some metric. I was wondering whether the same problem could be generalised and be proposed in completely empty...
  34. V

    Twin Paradox: Which Twin is Older?

    Maybe someone can explain the following twin paradox. There are two twins A and B. Twin A is shot straight up into the air with a very short and powerful cannon. Twin B remains on earth. Twin A goes up a distance and then falls back to earth. Which twin is now older?
  35. J

    Acceleration-free twin paradox

    I find the discussion about acceleration confusing. I want to avoid that. So try this scenario: Lucy is traveling at .6c relative to Bob. Just when they reach their point of closest approach, one kilometer, they synchronize clocks. As their distance increases, each of them sees a red shift...
  36. adoion

    Was Einstein lucky when not considering twin paradox as paradox?

    hi, Einstein did not even consider the twin paradox as problematic at all, he argued that it is a simple consequence of his special relativity? obviously he never gave a explanation of why the two twins don't age the same he instead left it to others to do so. was Einstein just having a hunch...
  37. sophiecentaur

    Faraday disc paradox; is there an equivalent situation with E fields?

    The Faraday paradox is a hard one to get ones head around and I was wondering if there is a similar scenario, involving an E field where there is / or is not an induced emf?
  38. D

    Twin Paradox Questions: Exploring the Observer's Perspective

    Hello all, I have not studied general relativity only special relativity, I apologize therefore if my questions seem low level. Thank you for your help. Three questions: The way in which I learned that the twin paradox is resolved is through the illustration of the way in which the observer...
  39. Stoney Pete

    Is the Real Number Line Actually Infinite?

    Hi guys, Here is a little puzzle I have been wondering about. I can't solve it, perhaps you can help. We know there are infinitely many real numbers on the number line. Indeed, already between 0 and 1 there are infinitely many real numbers. So if a real number is a point on the number line...
  40. DiracPool

    Acceleration and the twin paradox

    After many years of agonizing over it, I have still failed to come to terms with the twin paradox. Here's a brief review of my understanding and a few questions: A standard story is as follows: Twin A leaves the Earth for planet Zolan 10 light years away. Twin B stays on Earth. Let's say...
  41. kmm

    Time Dilation, Twin paradox etc.

    I know there have been a lot of other threads on this topic but I wanted to get some feedback on my thoughts on this. Time dilation is a result of Einstein's second postulate of SR, although the first postulate is what gives rise to the apparent twin "paradox". The common solution to the paradox...
  42. Demystifier

    A common-sense analogue of Skolem paradox?

    I am a non-mathematician who was reading about Skolem paradox. Since I am not sure that I understood it correctly, I would like to see a simple non-technical common-sense explanation of it. Unfortunately, I have not yet seen such an explanation that would completely satisfy me, so here I present...
  43. Ookke

    An apparent paradox with couple of frames

    Please see the pictures. In lab frame, we have rockets A and B initially at rest and clocks in sync. When clocks reach certain time T, both A and B accelerate at 45 degrees to up-right direction. There are inertial observers X and Y, which match the velocity x- and y-components that the rockets...
  44. L

    Twin Paradox: How Do We Calculate Ages and Coordinates in Different Frames?

    Homework Statement Anna is born in a spaceship, Bob is born on Earth (at the same time t=t'=0) just as Anna's spaceship passes Earth at 0.9c (EVENT A) Planet Z is 45 ly away at rest in Bob's frame. Anna flies past plant Z (event B) Meanwhile, Carl was born at the same time (t=t'=t''=0) on a...
  45. cqfd

    Integrating sin(x)*cos(x) paradox

    I am encountering a paradox when calculating the integral ##\int sin(x)\cos(x)\,dx## with integration by parts: Defining ##u = sin(x), v' = cos(x)##: ##\int sin(x)cos(x) dx = sin^2(x) - \int cos(x) sin(x) dx## ##\Leftrightarrow \int sin(x) * cos(x) dx = +1/2*sin^2(x)##. On the other hand...
  46. J

    Update: Negation of the Grandfather Paradox

    I originally posted the following: "... I believe I found a solution (or a negation) to one of temporal mechanics most enduring paradox: If you travel back in time, could you kill your own grandfather, thereby altering your future, even erasing yourself from existence? The short answer is NO...
  47. A

    What is the relationship between classical and relativistic Doppler formulas?

    Hi all, This is a follow-up to post 140 on April 9, 2013, the Triplets20.jpg of Triplet's Paradox. First of all, fantastic diagram. Is the following logic right as can be gleaned off that excellent diagram of Triplets20.jpg right? Both ships turn around (earth proper time 20 months) and...
  48. J

    Black holes and the centrifugal force paradox

    Hi Is someone interested in this topic ? I'd like to share my idea with you, PF people. I also designed a "reverse geometry" to illustrate this paradoxical effect. Thank you for your answer Jean-Marc
  49. M

    Twin Paradox Explained: Earth & Space Time Effects

    A person in the Earth (stationery frame) observes the clock in the spaceship (which almost moving at the speed of light) runs slow right? and an astronaut in the space-ship observes the clock in the earth, to him the clock also appears slow the same rate as the person observes the clock in the...
  50. H

    Proof That Multiverse Doesn't Exist

    If we assume that multiverse exists; it means that scientists goal are to prove this theory...but they are not successful in our universe. That means that there infinite universes where they have succeeded to prove it. Than scientist from one of those infinite universes, should be able to enter...
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