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. 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...
  2. 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...
  3. 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...
  4. 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}} =...
  5. 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...
  6. 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?
  7. 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...
  8. 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...
  9. 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...
  10. 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...
  11. 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...
  12. 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...
  13. 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...
  14. 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...
  15. 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...
  16. 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...
  17. Gravity

    Does Penrose's Andromeda paradox prove determinism?

    Article: https://en.wikipedia.org/wiki/Rietdijk–Putnam_argument
  18. 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?
  19. 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...
  20. C

    Twin Paradox with "home time"

    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...
  21. 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...
  22. 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...
  23. 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...
  24. 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...
  25. 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...
  26. 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?
  27. 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...
  28. 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...
  29. 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?
  30. 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...
  31. 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...
  32. 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...
  33. 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...
  34. 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...
  35. 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...
  36. L

    Twin paradox spaceship problem

    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...
  37. 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...
  38. 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...
  39. 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...
  40. 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
  41. 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...
  42. 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...
  43. F

    Conditional Probability -A Paradox?

    Homework Statement We've got a standard deck of 52 cards. We shuffle the deck well, then cut it into two piles of 26 each, a top pile and a bottom pile. We reach in and pull a random card out of the top pile, observing that it is an Ace. We then put it into the bottom pile, shuffle the...
  44. T

    Time Dilatation: The Twins Paradox

    We’ve all seen this little fellas up there. Two brothers, twins, in their 60’s. And they decide that one of them is going to take a trip into space, let’s say for a year, at 99% the speed of light. The other brother stays there, waiting for his twin to return, and looking at the light clock that...
  45. C

    Faraday's Paradox: Induced Current Explained

    disk and magnet spin together -> induced currentI ask can anyone properly explain why there is induced current in the setup?
  46. C

    Faraday's paradox: homopolar generator on a train

    There is a homopolar generator on a train moving at 215 km/h. The magnet of the generator is attached to the disk so they would rotate together, but they are stationary now, except that they are moving along with the train. Is there any current generated by the generator? I expect the answer...
  47. K

    Russel's Paradox: Understanding Sets and Contradiction in Proofs

    Prove Russel's paradox by contradiction and what does it tell us about sets? I tried doing it like this and I am not sure it is right. I supposed S was the collection of all sets and since S is a set S∈S. Now we can split this universe S into two parts: U(for the unusual that are part of...
  48. B

    Is Energy Conserved When Changing Frames of Reference in Space?

    Of course I am sure this is not a paradox but rather a problem in my understanding of the situation. But this question is bogging me, and I haven't found a satisfying explanation yet. Suppose you are floating in space, in an inertial frame. An object much more massive than you is moving with...
  49. N

    Problem analyzing rod-slot 2-D Lorentz contraction paradox

    I have encountered a difficulty which arises from my attempt to combine non collinear Lorentz transformations in analyzing the following problem: A thin rod is cut from a metal plate leaving a slot of exactly the same size. The two are separated and set in motion thus: the rod lies along x...
  50. T

    Can a book from the future save a woman's life in the past?

    An immortal woman who is about to go back in time is mailed a book from an unknown address. Inside the book reveals explicit instructions on how not to die while in the past leading up to the present day. The book is written by her future self and mailed to herself by her future self who is now...
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