What is Paradox: Definition and 1000 Discussions

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. C

    [Question] About the radio signal for Twin Paradox

    There is an example for the radio signal for Twin Paradox from the book "Classical Dynamics of Particle and Systems, Thornton, Marion". Refer "1.jpeg", example 14.5, it said that "However, Frank continues to receive a signal every 3 years for the 8 years it takes the last signal Mary sends when...
  2. H

    How Does the Twin Paradox Affect Aging in Space Travel?

    Everyone knows that paradox. In true we can say who person is standing,so If we say that the person in Earth is standing,then the clock of astronaut will run slower. Else,if we say that astronaut is standing and that Earth is moving,we see the clock of Earth's person to run slower. So in true...
  3. W

    Twin's Paradox: Q&A on Acceleration, Velocity & Time Dilation

    Before people start bashing me for not reading up on other threads, I did try and perhaps I am not physics-savvy enough to understand but I just found the answers to be contradictory and confusing. So, here are two scenarios that confuse me: Scenario 1: Two twins start off on earth. One...
  4. A

    Momentum conservation in the twin paradox

    I was thinking about one of the many resolutions of the so-called 'twin paradox' within SR framework. I realize many methods of resolving this have been proposed, but I am curious about the particular solution that uses 'acceleration' of the traveling twin, to create the required asymmetry for...
  5. Superposed_Cat

    How Does Hawking Radiation Influence the Black Hole Information Paradox?

    Hi all, to begin this is my understanding of hawking radiation. A particle/anti-particle pair is generated. one particle outside the event horizon of a black hole, the other inside. The gravitational force "boosts" the one particle into being real. this energy is compensated for by endowing...
  6. T

    Time Paradox: Calculating Time Dilation for Objects Moving at 90% Speed of Light

    Suppose an object "O" is traveling towards me at 90% speed of light which is placed at 1hr c away, then how much time in "MY Clock" would it take to reach me? I calculated it to be 1hr and 6 mts, am i right? But on the other hand I'm the one who is moving towards the object "O" so by time...
  7. J

    What causes the divergence of acceleration in the parallel plate system?

    Consider the system below comprising a pair of oppositely charged parallel plates, connected by a rigid rod of length r, constrained to move in the x-direction. The forces on the plates from the Coulomb electric fields and the magnetic forces are all in the vertical direction so that they do...
  8. T

    Paradox within relativity of simultaneity

    Recently i found a problem with relativity of simultaneity, its a paradox within relativity of simultaneity. It is probably unexplainable and i would like to publish it without losing my credit. Can anybody tell me any way to publish it? I'm not rich to spend money, but is there any simple way...
  9. T

    Bell’s Spaceship Paradox In Another Way

    This is another version of bell’s spaceship paradox. Consider two spaceships A & A’ separated by a distance L, and are tied by a non elastic thread. They are on earth. This time the two spaceships are not moving instead I'm moving. I’m in a distant planet and i starts to accelerate and reach at...
  10. T

    Is the Bell's Spaceship Paradox a Result of Relativity of Simultaneity?

    In relativity of simultaneity, it is said like simultaneous events for one observer is not simultaneous for another. Does that mean events been seen from one observers point of view may not be true? For example consider the bell’s spaceship paradox From my point of view the "silk thread"...
  11. J

    The paradox of Hawking radiation - is matter infinitely compressible?

    The hypothetical Hawking radiation means that a set of baryons can be finally transformed, "evaporate" into a massless radiation - that baryons can be destroyed. It requires that this matter was initially compressed into a black hole. If baryons can be destroyed in such extreme conditions, the...
  12. P

    Can a twin paradox occur if one twin never changes direction or stops?

    Hi Everyone, I've managed to confuse myself with a mutilated thought experiment. A half twin paradox. Imagine a twin, Paul travels away from Earth at 8/10c while peter stays at home. Because of time dilation paul reaches a planet by his clock, in one year. Peter registers Pauls arrival at...
  13. C

    Exploring the Twin Paradox: Acceleration & Aging

    http://en.wikipedia.org/wiki/Twin_paradox I read a little bit about this, and am a little bit confused. I always learned about reference frames. When I jump, you can say that I am moving away from the earth, or the Earth is moving away from me. Why is this any different for near-light travel...
  14. K

    Calculating Speed for Time Dilation in the Twin Paradox

    Homework Statement "A star is 5ly away. If an astronaut wants to travel there and back and only age half a year, at what speed β = v/c do they need to travel?" Homework Equations \gamma = \frac{1}{\sqrt{1 - v^2/c^2}} \Delta T = \gamma \Delta T_0 so \Delta T = \frac{\Delta T_0}{\sqrt{1 -...
  15. H

    Twin Paradox & Neutron Speeds: Questions Explored

    I have make many threads about this topic because I am really interested. I reading that from an pdf,but I have some "idiot" questions too. 1)A guy told me that If you run in other speed from an other you see his clock slower. I have hear about paradox of twins,that this with biggest speed...
  16. E

    Russel's Paradox in Naive Set Theory

    I realize that Russell's Paradox in naive set theory is considered to be, well... a paradoxical fallacy. Despite the fact that it is paradoxical and goes against logical intuition, is it really illogical though? It seems to me that the method in which the paradox arises is perfectly sound and as...
  17. G

    Lebesgue measure and the Banch-Tarski Paradox

    I have finally finished reading the proof of the Banach-Tarski paradox. I think the proof was the standard versoin I see around the internet, with the the group G of rotations phi and psi and so on. I was wondering how the proof fails as a result of lebesgue measure on the set?
  18. StevieTNZ

    Hardy's Paradox - Which Way Information

    I have three quick questions regarding the experimental set-up attached, in relation to Hardy’s Paradox. What possible detections are available, according to Quantum Mechanics, and do those detections indicate, for the electron and the positron, which path they took? I’m guessing not as at...
  19. F

    Opposite of Gabriel's Horn Paradox

    We are all familiar with Gabriel's Horn, where the function f(x) = 1/x generates an infinite area but a finite volume when revolved around the x-axis. So the other day I stumbled upon a particular interesting integral: ∫ from 0 to 1 1/x2/3 dx Instead of infinite limits of integration, we...
  20. D

    Special Relativity - time paradox question, not sure if it's right

    Homework Statement 2 identical clocks are synchronised in a lab on the equator. One clock is carried around the equator in 24 hours at a constant speed. Given that the radius of the Earth is 6.4 x 10 ^ 6 m, find the difference between the times registered by 2 clocks when the traveling clock...
  21. Z

    Modified Twin Paradox in Special Relativity

    The problem statement Suppose the universe is a 2-torus, thus there exists a spatial path that you will go back to where you start eventually. Let Observer A and Observer B travel on this closed path. Observer B is traveling at a constant speed of 0.9c relative to Observer A, where c is the...
  22. B

    Understanding the Complex Number Paradox: Exploring Its Origins and Solutions

    Hi, How can we explain this paradox: Thanks in advance.
  23. R

    Understanding the Twin Paradox: A Simple Explanation

    Please explain me simply about twin paradox..
  24. R

    Interesting Infinite Powers Paradox

    Recently, an AT&T commercial has been running on TV where a moderator asks some children about the largest number they could think of. At the end, one kid replies “∞ times ∞”, which of course is simply ∞2. Natually, one can instantly think of a larger number: ∞∞. But then, that got me...
  25. C

    Can Area Remain Constant While Dimensions Expand? A Paradox in Geometry

    Imagine an box with initial dimension x_0 and y_0 with a cavity in the centre with area R^2 . Let's say the box gets stretched in the y-direction but that it's area and the area of the cavity must stay constant. A=x_0y_0-R^2=x(t)y(t)-R^2 Differentiating with respect to time gives...
  26. A

    Magnetic force paradox Hall Effect

    Hello, I was taught that moving charges in an external magnetic field experience force. Okay. I wondered that if the observer was moving with the same velocity as the charge is what would happen? I studied in one book about field transformation and came to know that the charge will...
  27. Z

    A question on a tweek of the Twin Paradox

    now the resolution of the twin paradox as put down in textbooks i have read relies on one observer being accelerated and one not so one can claim to be inertial and thus priveledged - this i always felt to be a cheat - even edward teller uses it in conversations on the dark secrets of physics -...
  28. A

    When Clocks Meet: Investigating Time in Einstein's Special Relativity

    Dear Friends, Discussion of the Einstein's Special Relativity clock paradox is often complicated by the role of accelerations and objects following curved or polygonal paths. In the following example considers the clock paradox in a situation which only involves linear motion. Imagine a rod...
  29. O

    Paradox in evaluating the Lorentz field in a dielectric

    Can someone help me in understanding where I am wrong when thinking about the derivation of the Lorentz field in a dielectric. I give the derivation in italics (although the familiar reader should not need to read it) and after that I present the paradox. The basic idea is to consider a...
  30. G

    Is there a time paradox in Big Bang cosmology?

    In this post, I am going to assume the truth of the standard model of cosmology, which says that the universe is expanding as time progresses from some infinitely compressed state. The paradox Has anybody heard anything like this? Any thoughts on how to "solve" it?
  31. N

    Bell's Spaceship Paradox and Length Contraction

    Can someone please clarify for me whether length contraction in special relativity is considered a physical effect (a contraction of a cohesive material) or a kinematic effect (applied to the space the material occupies)? I've been thinking about Bell's Spaceship Paradox this week and realized...
  32. E

    Confirm: Smooth Twin Paradox Intuition

    I'd like someone to confirm whether I am on the right track here. Most formulations of the twin paradox involve a sharp turn-around with infinite acceleration. I suppose that there is an SR-only description of a non-infinite acceleration - a kind of 'smooth' version of the twin paradox. But my...
  33. D

    Ladder Paradox: Understanding the Contradictory Length Contraction Phenomenon

    Hi, I've red a lot these days about the ladder paradox and I have a question about it, but firste let me quote wikipedia so I can describe you the problem: "In the context of the paradox, when the ladder enters the garage and is contained within it, it must either continue out the back or come...
  34. C

    Ehrenfest's Paradox: Resolving the Kinematical Solution

    I'm reading about Ehrenfest's paradox where one considers a rotating disk. If one let r' be the radius of the disc in an inertial frame and r be the radius of the disc when it is at rest. Then the periphery must be Lorentz' contracted such that ##2\pi r' < 2\pi r##, but since the radial line is...
  35. K

    Father-Son Paradox: Explaining Time Dilation

    This is an extension of twin paradox of STR. Suppose when the father was 30yrs old, he got into this flight which moves close to c. After a while in that he comes back to see his Son older to him! I'm sure this is a possibility from time dilation. Is this really possible? If so, how is the...
  36. D

    Andromeda paradox and determinism?

    Can somebody explain the implications of the well known Andromeda paradox in a metaphysical sense? First, does it state that all events are determined? If one observer already knows what happens on the Andromeda galaxy, could it be possible that that event still happened in an indeterministic...
  37. H

    E&M Faraday's Paradox: Understanding the Contradiction

    A conducting disk is rotating under a uniform magnetic field. Using Lorentz force F = qv x B, we can conclude that emf produced. Using Faraday's law, ∫E dl = 0 for any closed loops since there is no magnetic flux change. So E = 0. Contradiction ?
  38. B

    What is the final number of balls in the Ross-Littlewood vase paradox?

    Ross-Littlewood vase filling paradox (from Wikipedia): To complete an infinite number of steps, it is assumed that the vase is empty at one minute before noon, and that the following steps are performed: The first step is performed at 30 seconds before noon. The second step is performed...
  39. Jarvis323

    How Does Relativity Explain Different Observations of the Same Event?

    In order to attempt to understand relativity, I thought of the following 'paradox', which I hope to resolve mathematically. An astronomer makes a terrifying observation. An asteroid is on a crash course towards Earth at almost the speed of light. An ultra advanced nuclear rocket is...
  40. H

    Angular momentum in ElectroMagnetic fields(Feynman's Disk Paradox)

    In Griffiths book, "Introduction to Electrodynamics" example 8.4 he calculates the angular momentum density for a set up that is a version of Feynman disk paradox. His answer for the angular momentum points in the z direction. But if we you assume that the r vector has component in the s...
  41. DevilsAvocado

    Relativity Paradox – RoS: Trains, Tunnels & Guillotines

    Professor Mike Merrifield from the University of Nottingham has made this excellent video for Sixty Symbols, explaining the apparent paradox of Relativity of Simultaneity: * Relativity Paradox - Sixty Symbols * https://www.youtube.com/watch?v=kGsbBw1I0Rg After this video, it should be...
  42. M

    Twins Paradox: Why One Twin is Older When Reunited

    Hi All. Layman question. In the twin's paradox, why one of the brothers is older when they meet again?. if movement is relative. What determines which of them ends up older? Hope i explained myself. Thanks.
  43. V

    Time Travel Paradox Ideas - Except Grandfather

    Hey guyies, can i get some really interesting and crazy paradoxes, except the grandfather one, thank you
  44. C

    What is the Angular Momentum Paradox?

    Consider two concentric circles of radius r1 and r2 as might be drawn on the face of a wall clock. Suppose a uniform rigid heavy rod of length | r2-r1 | is somehow constrained between these two circles so that one end of the rod remains on the inner circle and the other remains on the...
  45. T

    Capacitors Paradox: Can Energy Transfer Require Less?

    if two equal capacitor one of then is charged and the other is not.then the switch is closed, half of the stored energy of the 1st capacitor will be lost. if there is a way to move electrons from one of the positive plates to the other positive of the other capacitor,will it require less...
  46. H

    The big bang's optical paradox

    Optics would predict that objects appear bigger in size as higher the redshift and the density should be the same independent of the galaxys redshift. As far I know this is not supported by observations. Anybody has an explanation please? sdgs_cat
  47. D

    Russell's paradox and logical errors in the proof

    I need your opinion/help, guys. Well-know American logician H. Curry once expressed the opinion that in spite of the fact that it seemed to be absolutely impossible to explain Russell's paradox in terms of conventional 19th century logic, it may happen in modern days that some error would be...
  48. S

    What is the Mystery of the Magnetic Paradox?

    Homework Statement Does anybody have any idea about magnetic paradox.i saw a university question where they asked to write a short note on it.i searched google , griffiths, jackson , feynman.all my search has gone in vain.i am doing bsc hons in physics and in my 2nd year course of studies...
  49. Ookke

    About man falling into grate paradox

    http://en.wikipedia.org/wiki/Ladder_paradox#Man_falling_into_grate_variation In the resolution it says: "It should be stressed that, since this bending occurs in the rod's rest frame, it is a true physical distortion of the rod which will cause stresses to occur in the rod." I wonder if...
  50. J

    Strange Twins Paradox: A Crackpot Physics Mystery | Discover the Solution Here!

    Hi, I did a search for "crackpot physics" and found https://www.physicsforums.com/showthread.php?t=111647 and then this forum. A friend of mine found some strange twins paradox on the net but he can't remember where. Neither of us can figure out the solution, but it must be crackpot...
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