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. A

    Spring Paradox (apparently). Energy problem with one vertical spring.

    Apologies if this is too basic, but I've been studying for a while and I'm stuck. Homework Statement Spring paradox. What is wrong with the following argument? Consider a mass m held at rest at y = 0, the end of an unstretched spring hanging vertically. The mass is now attached to...
  2. Z

    Apparent paradox in cardinalities

    I'm strictly amateur at number theory (Not even studying it, just playing around for fun), so forgive me if I'm being foolish here. I've found a "proof" of something that is clearly wrong, and I can't find my mistake, so I'd appreciate anybody's help in figuring out what I did wrong. Also please...
  3. D

    Experimental verification of Ehrenfest Paradox

    I am not completely convinced that the modern resolution is correct. Is it? Is anyone aware of any experiments that have been done that relate to this effect? Reference: http://en.wikipedia.org/wiki/Ehrenfest_paradox
  4. T

    Inverse square law resolves Olbers' paradox

    Treatment originally used to discard inverse square law as solution to Olbers' paradox was not set up correctly. If we include sensor (camera) in the treatment and model light as photons the result describes what we actually see.
  5. J

    Bell Paradox Questions - Diagram help

    Consider the following thought experiment. Two spaceships are initially floating in a region of space far removed from other matter. They are at rest with respect to each other, and with respect to some inertial reference frame F. There is a distance L between them. At some time, t=0, as...
  6. T

    Gravitational Field Paradox Explanation?

    Gravitational Field Paradox Explanation?? Hi everyone. If electric and gravitational field has an infinite nature-meaning that the effect one charged particle has on another charged particle always remains even though it diminishes over distances but can never reach absolute 0-then how is this...
  7. T

    Why do smart gamblers sometimes bet on outcomes with negative expected value?

    Not long ago I was surprised to learn that when trying to maximize the expected long-term growth rate of your money, it is sometimes necessary to bet on an outcome that has negative expected value (in addition to outcomes that have positive expectation). See...
  8. R

    Does the Twin Paradox Involve More Than Just Velocity?

    I know the twin paradox has been answered a lot on here, sorry for bringing it up again. I thought i about had it figured out but then i read a few things that confused me again. For starters, its starting to sound like time dilation won't happen unless there is a complete round trip, that...
  9. B

    Geomagnetic Reversal 41k BP 240 years Paradox? Mechanism?

    There has been a series of papers recently published that provide observational data that indicates that something is cyclically abruptly changing the geomagnetic field. The rapidity of the observed geomagnetic field changes cannot be explained by a core based mechanism. There is no...
  10. bcrowell

    Why does the buoyant force decrease in Supplee's submarine paradox?

    Supplee's submarine paradox arises when you consider a submarine moving horizontally at relativistic speeds. (Never mind that this would obviously destroy the sub.) When at rest, the sub was neutrally buoyant. In the moving sub's frame, the water is more dense, so buoyancy is increased, and the...
  11. A

    Is asymmetric time dilation in twin paradox possible in SR?

    I am trying to understand if SR can explain a real, measurable velocity time dilation as seen in experiments/observations like GPS satellite or Bailey et. al. Let us say we have twins sitting in their identical, individual spaceships in space, close to each other, and far away from any large...
  12. B

    Speed of Light Paradox: What Did I Miss?

    Hi, there is something I can't understand: Consider a stationary observer at A. Now consider an observer B in a train that moves with constant velocity v with respect to A. In the train, B tries to measure the speed of light using an empty tube of length L0 (proper length as measured by B). He...
  13. X

    Can Knowledge of the Future Alter Its Course?

    Given a Universe abiding solely by deterministic laws, Laplace's reasoning seems to make perfect sense. So let us take this deterministic Universe and imagine within it a scientist to whom the, let us call it: the ultimate formula, was made accessible. So, being capable to plug this hypothetical...
  14. W

    Paradox about Maxwell near an accumulation of charge

    Hi. I am trying to understand Maxwell's equations. I am used to Gaussian units. The following sums up what I do not understand. (Or at least one thing I do not understand ... ) Let x0 be a position situated in a vacuum, with no photons in it, next to an infinite pane of glass. Ions arrive at...
  15. G

    The Twin Paradox: Triplets Edition

    A variant of the classic twin paradox. There are three triplets, who have the boring names of Adam, Bob and Charles. In Charles' "rest" frame, Adam and Bob get into identical rocketships, jet off in opposite directions and return a year later. To Charles, Adam and Bob's paths are...
  16. S

    Planck Length Paradox: Radius & Area

    Assuming that a Planck length is the smallest unit of distance, I propose this: Assume there was a circle of radius r and had an area of A. If I would increase this circle's area by 1 Planck length^2, would the radius change? The radius would theoretically change by less than a Planck...
  17. R

    Twin Paradox Problem: Do Twins Age Differently?

    twin paradox problem!? ok it's about the twin paradox the guy on spaceship goes at 90% of C (say) but since both the twins see each other's clocks equally slow and if one sees other at 90%C then the other one also sees his twin at 90%C in opposite direction. then how on returning the twin on...
  18. S

    Ehrenfest Paradox + Twin Paradox

    1. The Ehrenfest Paradox After watching some of the posts here, I am not sure if I can conclude - The circumference-radius ratio is INDEED not 2π, but with a factor γ (which means Euclidean geometry is not necessarily correct in relativity, and the radius 'cuts through the circumference' ?) ...
  19. J

    Attempt on Twin Paradox via Minkowski diagrams

    This is an attempt to solve the twin paradox via two Minkowski diagrams with a few questions attached. Note that there might be mistakes in this drawing i will fix in the course of this thread in case someone notices any. First, let me explain the two Minkowski diagrams in the drawing first...
  20. J

    Discover the Fascinating Olber's Paradox in This Cartoon Cosmology Video

    Cosmology isn't my thing but a friend showed me this and I thought it was great so I'll leave it here too for anyone interested: https://www.youtube.com/watch?v=gxJ4M7tyLRE
  21. soothsayer

    Paradox of non inertial forces in relativity

    Ok, so I've been thinking of a certain paradox in relativity that I can't seem to resolve: We have two observers, one in a "stationary" frame outside the Earth. This observer is looking down on Earth at another observer sitting at rest with respect to the surface of the Earth, but obviously...
  22. S

    Paradox of uniform prob. distribution on Z+ vs cardinality, etc.

    There are no actual paradoxes in mathematics (we hope). There are only things that appear to be paradoxes to fallible intuitions. Here is one that bothers me. There can be no translation invariant probability measure on the non-negative integers. Yet it is possible to imagine a general class...
  23. B

    Which Train Explodes First in the Time Dilation Paradox?

    Hi, I am new to this forum, and I wish I get some help here. I really can't find any solution to this paradox; I am going to deny all the special theory of relativity because of this. The paradox is very simple, here it is: Consider two persons sitting on two adjacent trains at rest...
  24. zoobyshoe

    Medical Exploring the Obesity Paradox: Fitness Over Weight Matters

    And quite a paradox it is. Goes against everything we have been taught: http://www.nytimes.com/2012/09/18/health/research/more-data-suggests-fitness-matters-more-than-weight.html
  25. S

    Paradox of star - mesh transform ?

    Dear All, I have encountered the following situation: Given a node that is connected through n resistors to n ports. One if the resistors is a negative resistance and equals to minus of all other resistors in parallel. \frac{1}{R_n} =- \sum_{i=1}^{n-1} \frac{1}{R_i} Using the well known...
  26. E

    A Twin Paradox Question, totally lost.

    Homework Statement Planet W is 12ly from earth. Anna and Bob are both 20 years old. Anna travels to planet W at 0.6c, quickly turns around, and returns to Earth at 0.6c. How old will Anna and Bob be when Anna gets back? Homework Equations The Attempt at a Solution I've tried...
  27. T

    A Universe with no Twin Paradox

    People are intrigued by Einstein's Special Theory of Relativity. They are fascinated by the Twin Paradox and the slowing down of moving clocks. However it is often forgotten that Einstein's SR, in spite of being weird to the day to day speeds we are accustomed to, saved Physics from something...
  28. N

    Dichotomy paradox reverse engineering

    We know we can biject the segments of size 0.5, 0.25, 0.125, … to the segments of size 0.25, 0.125, 0.0625, …, furthermore we can biject these segments to the segments of size 0.125, 0.0625, 0.03125, …, and there is no end to it. So, we can use index #1 for segment 0.5. We can as well use index...
  29. A

    Why Russel's paradox and barber paradox occur

    Why do paradoxes like Russel's paradox and the barber paradox occur? Is something wrong with the definition or what?
  30. R

    Twin Paradox: Time & Speed Explained

    hi .. i don't understand in the twin paradox and in general and special relativity why time changes if speed changes thank you
  31. V

    Chain Rule Paradox or Am I Doing Something Wrong?

    If h(x) = ax, g(x) = bx and f(x) = g(h(x)). Wouldn't h'(x) = a? And g'(x) = b? And f'(x) = ab? But the chain rule says f'(x) must equal h'(x)g'(h(x)), so that means f'(x) = ab(ax) = (a^2)bx. Am I missing something obvious?
  32. S

    My Particularly Troublesome Version of the EPR Paradox

    In quantum physics, a wave function instantaneously collapses once an observable is measured. For instance, if an electron's angular momentum in the z direction is measured, then the angular momenta in the x and y direction immediately become indeterminate due to the Heisenberg Uncertainty...
  33. I

    Twin paradox on another planet

    Hello! I'm new here, and already did a search. Sorry if the answer is elsewhere, I just couldn't find it! I'm writing a sci-fi novel and have been brushing up on general and special relativity. I'm running into a small problem with the twin paradox, and how to describe it from another planets...
  34. S

    Does Bell's Paradox Suggest String Shouldn't Break Due to Length Contraction?

    As I understand, we should treat length contraction as if all space in the moving frame is contracted-- that is, the distance between two objects as well as the objects themselves are cotracted by a factor of gamma. If this is correct, wouldn't the string in Bell's paradox NOT break- because...
  35. C

    Apparent paradox with angular and linear motion

    A friend raised an observation which I thought would be easy to explain. But it seem I have a gap in my physics knowledge... An object (rigidbody) is stationary in zero gravity empty space. In the first situation we apply an impulse to its COG and its linear momentum changes, and no angular...
  36. D

    Schrodinger's Cat- Cat variations causing loopholes in the paradox?

    So, we probably all know by now the Schrodinger's cat thought experiment. A cat is in a box with a small amount of radioactive material. If it happens to give off radiation, it sets off a geiger meter, which causes a hammer to break a small vial of poison gas. Until you look in the box, the cat...
  37. X

    Is there an answer to Zeno's paradox of Achilles and the tortoise ?

    Is there an answer to Zeno's paradox of "Achilles and the tortoise"? I'm not sure if there is an answer or way to resolve this paradox nor do I know if it would go in the category of physics or math (even though I've heard that as a math problem it was solved a few centuries ago).It goes...
  38. R

    Can Hilbert's Paradox Be Solved With a Simple Command For Guests to Move Rooms?

    In Hilbert's paradox to accommodate a new guest you move guest 1 to room 2, guest 2 to room 3 and so on this will make space for a new guest. I assume that guest 1 has to wait for guest 2 to move to room 3 before he can move to room 2 thus all guests have to wait for guest n to move to room n+1...
  39. B

    Why is Russell's Paradox not just wordplay?

    Suppose I have a set that contains all sets that it does not contain. Obviously no such set exists because the thing I just said makes no sense. I might as well say consider the natural number which is greater than zero and less than one. No such thing exists. So I don't understand why Russell's...
  40. D

    Time Travel Paradox Involving Couples

    Has Anyone ever thought of this time travel paradox before? That a couple or more (some men and some women ok) went back in time via a Time Machine and started, i.e. seeded the Human race? That is the Human Race is a Perpetual Loop? What would this be called?? A feedback loop?
  41. M

    Bell Spaceship Paradox: A and B's Viewpoint

    Hello, Suppose, A and B spaceships are moving with constant acceleration. There is a string tied to spaceships center to center. A is on left of B and B is on right of A. C is outside observer. As speed increase, A sees that B going further ahead, and B sees A going further behind. So, from...
  42. P

    The Zeno's paradox and one of its variations

    Hi, I was learning about collisions, and I stumbled upon this materials, which is interesting because a guy who wrote it gave this interesting example. He was talking about "somewhat inelastic collisions", as he calls them, and he gave an example of a ball bouncing of the floor. Here are the...
  43. C

    Electrodynamics - I'm trapped in a stupid paradox - pleas help

    Homework Statement B = variable magnetic field, of constant direction (e.g B = b cos(wt) N, where N=const vect) A = magnetic potential vector of B R = vector from some origin O to a point M It is assumed that no exterior electric potential is present. Problem: to find the...
  44. T

    Exploring the EPR Paradox: QM and Locality

    Sorry, I have 2 doubts about the EPR paradox. 1) Just check out if I am ok: What EPR proposed was that QM suggest that if two entagled particles, for example photons, prepaired in some special way, get away from each other then: a) if we measure their x-spin then one particle will get the...
  45. JimiJams

    Time Dilation and The Twin Paradox?

    Hey everyone, I've searched the threads for an answer to my question but came up short. Basically what I want to know is how does time dilation relate to the twin paradox. I'm a newb to relativity and just started reading about it last night. I hit this bump and I'm trying to get over it...
  46. S

    How can the Pole&Barn Paradox be solved?

    I have studied in some details pole&barn paradox and I thought I could solve the following paradox, but sadly I couldn't! Please help me with it so that I can understand special relativity better. Thanks in advance for any help. The paradox: There are two trains T1 and T2 of equal proper...
  47. H

    The Twin Paradox and the Equivalence Principle

    I'm having a little trouble understanding the equivalence principle explanation of the twin paradox. I understand that the resolution to the paradox according to the equivalence principle is that the non-traveling twin has a higher gravitational potential energy in the pseudo-gravitational...
  48. V

    Who Ages Faster in the Twin Paradox?

    Hi, I am a little confused with this paradox. I asked my professor about it and he didnt really give a convincing answer. So the scenario basically seems to be some twins on earth(or anywhere) at rest, and then one leaves at relativistic speed for some time then comes back to see that his/her...
  49. M

    Is this a good way to explain Skolem's Paradox?

    "The paradox: Let T be a standard first-order formulation of ZFC. Assume T has a model. By Skolem's Theorem, T has a countable model M. Since T ⊢ ∃A(A is uncountable), M ⊨ ∃A(A is uncountable). But how can M—i.e. a model that “sees” only countably many things in the universe—“say” some sets...
  50. T

    Paradox of motion implies discrete space?

    Came across this video which says that a moving object has to cover infinitely many intervals in order to get from one point to another and because of this motion couldn't really take place and since it does take place, its a paradox. youtube.com/watch?v=u42Y3RbP7JE Since motion does take...
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