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. S

    Electric Field due to infinite charge distribution seems a paradox

    Suppose everywhere in space charge is distributed with uniform and constant volume charge density. What will be Electric field at any point in space?? 1>..Symmetry demands it to be zero, 2>..if I consider the space to be a sphere of infinite radius with constant charge density on its volume...
  2. S

    Slightly Modified Olbers Paradox Question

    I understand the resolution to the typical statement of Olber's paradox, that is, that with a finite horizon distance only light up to a certain distance will have reached Earth. However, let's say that we modify the contents of the universe such that we have an infinite horizon distance. Why...
  3. alexmahone

    Travelling to the future (paradox)

    Some time ago, I watched a Stephen Hawking documentary which said that you could travel to the future if you went at a fraction of the speed of light for some amount of time. The explanation was this: Consider an observer O at rest. Let the time traveller be T. O sees T whiz past him and...
  4. C

    Did I just create a coin tossing paradox?

    Gibson's Coin Paradox: You have 2 coins with you. There is absolutely no way that you can tell the difference between them. The coins are fair, meaning the chances of getting heads is equal to the chance of getting tails so a 50% vs. 50% chance. You put on a blindfold and drop the coins, one...
  5. M

    Measuring which path in Hardy's paradox, results

    I am reading a paper from Yakir Aharonov and others revisiting Hardy's paradox and I have a question. Let me state the notation first as brief as possible so that we can use it in the discussion: * a positron e+ goes through either the overlapping arm o+ or the non overlapping arm no+ of a...
  6. A

    Archimedes Paradox: Exploring an Alternative Explanation

    We are preparing a physcs quiz and are planning to use the following problem If we have a wooden block balanced at the junction of two immiscible liquids then we have the buoyancy of the two liquids balance the weight of the block.The lower liquid will exert your normal upthrust but the upper...
  7. C

    Moravec's Paradox: AI Reasoning vs Sensorimotor Skills

    Hey! Browsing the web, I came across a pretty interesting idea(at least for me) which I haven't seen people in this forum discuss. http://en.wikipedia.org/wiki/Moravec%27s_paradox In just says that high level human cognition is a much easier problem for AI researchers to solve compared...
  8. S

    How to create language without self-contradiction?

    Alfred Tarski diagnosed the Liar Paradox as arising only in languages that are "semantically closed", by which he meant a language in which it is possible for one sentence to predicate truth (or falsehood) of another sentence in the same language (or even of itself). To avoid...
  9. B

    The Titration Paradox: How Can pH = 7 at Two Different Volumes of Titrant?

    I'm a little boggled by a strangle titration problem that seems to contradict what I know about titration. I hope someone can resolve this seemingly strange phenomenon. Suppose you have 0.1M of 50mL HCl. You begin to add 0.1M of NaOH titrant. Assume that Na and Cl ions do not hydrolyze. Find...
  10. L

    Capacitor Paradox: How Can Voltage Stay Constant When Charge Density Increases?

    So as I was doing my sample physics midterm, I realized a paradox or a concept that I just haven't fully grasped, hence I see a problem. Homework Statement Suppose we have two parallel plates of a capacitor with: capacitance C, area A, distance of separation D, a constant voltage V=10V...
  11. J

    Relativity and The Stopped Clock Paradox

    Might there be anyone here who knows the math to work this one out? Stopped Clock Paradox Simplified "The speed of light is the same for all observers." Scenario The stationmaster has set two synchronized stop-clocks along side the track. The stationmaster placed the clocks exactly 8 μls...
  12. J

    What happens when you fall into a black hole?

    sorry if my understanding of high level physics is cursory, i didnt major in it at ptown even tho i always had a hard on for physics and slept through ap phys in high school because the concepts were infantile to me. from my understanding its conventional wisdom that a person falling into a...
  13. K

    What happens when two length contracted ladders move through the same garage?

    So what happens if we have TWO ladders moving in opposite directions through the same garage? Figure 4: Scenario in the garage frame: a length contracted ladder entering and exiting the garage Figure 5: Scenario in the ladder frame: a length contracted garage passing over the ladder...
  14. M

    Twin Paradox Explained: Long Outbound & Short Inbound Leg

    Hello, All I read the article: http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_paradox.html But, I cannot understand how just asymmetry (without acceleration) can cause less age of moving observer. The article says: I cannot understand why do Terence see an...
  15. I

    Time curvature and twin paradox.

    Can the twin paradox provide us with insight into time curvature? If my twin boards a ship that can travel near the speed of light, special relativity says that on arrival back on Earth, my twin should be younger that I am. Has my twin experienced a time curvature?
  16. R

    How Does Calculus Resolve Zeno's Paradox of Motion?

    It is said the sum of infinite series 1/2+1/4+1/8...=1, i.e it say there are infinite points. It also means if it goes on like this it will approach the limit which is 1 in this case but never ever will it be able to reach 1. Or in other words it says 1 is the point that would never be...
  17. K

    How does the duration of acceleration affect the Twin Paradox?

    [later edit: Sorry for the title -- I am glad to see this was interesting enough to spark discussion.] Twin A takes off and leaves Twin B behind. Rather than switching on the reverse-thrust, slowing down, and beginning the journey back home (an acceleration that would be distinctly detectable...
  18. S

    Acceleration doesn't cause the Twin Paradox?

    Acceleration doesn't "cause" the Twin Paradox? In a recent review of a physics textbook, the reviewer is critical of the author of the book because the the author doesn't correct the persistent notion of many students that it is the acceleration of one of the twins that "causes"[reviewer's...
  19. beowulf.geata

    Tug-of-War Paradox: Forces & Balance in Red/Blue Contest

    Homework Statement Imagine a tug-of-war contest between red and blue teams. (a) Early on in the proceedings, the two teams are equally matched and so there is no movement of the rope at all. (b) Having been more moderate over lunch, the blue team begins to pull the red team along at an...
  20. Q

    Twins Paradox - but with a different spin

    While attempting to wrap my head around the classical Twin Paradox, I asked myself the following. So far I have not been able to reach a well reasoned answer... which is no big surprise. :) Twins (A and B) are oriented in space such that A could be said to be standing on B but facing in the...
  21. R

    Bell's Spaceship Paradox - Shouldn't the thread stay connected?

    Hi, I am trying to understand this Bell's Spaceship Paradox , which is basically asking when there is a thread connected between two spaceship (A,B) and an observer C observes a "constant" acceleration, then whether this thread will break or not by Lorentz Contraction. I think the problem...
  22. X

    Twin paradox and time dilation

    I like astrophysics,so i read books relating to it.I am also determined to make my career in the same.At present i am reading a book ,which includes brief about Einstein's 'Relativity and special relativity' theory.It also explains to some extent the 'Twin paradox' and 'Time dilation'...
  23. G

    Time Travel Paradox: Can It Happen?

    I just got done watching Stephen Hawking's Into the Universe episode 2, which is about time travel. They think that time travel into the past is most likely impossible simply because of paradoxes (go back in time, and kill yourself before you went back in time). However, tiny wormholes the...
  24. S

    Does Earth's Movement Affect the Twin Paradox in Space Travel?

    If in the twin paradox instead of the twin traveling to the distant star let's say he stays and the Earth along with that star moves (imagining a rod joining Earth and star moves) and the star reaching this twin goes back at the same speed(along with earth) now i guess the twin whos stationary...
  25. G

    Twin Paradox: How Much Time Has Passed on Earth?

    Let's say there are two synchronized clocks on Earth. One leaves the Earth going at .8c and travels in uniform motion for one year. At the one year mark the clock is handed off to another spaceship coming towards Earth at the same speed of .8c. The clock eventually makes it back to Earth...
  26. L

    Paradox of Bernoulli's Theorem and Moving Frames

    Here is a paradox that came to my mind during my fluid mechanics course last term. I don't know the solution to it: We have this experiment in which we hold two sheets of paper parallel to each other and blow between them. They are brought closer to each other...
  27. S

    Twin Paradox: Solving Confusing Explanations

    This question about the twin paradox(twins A,B). I hope everyone knows the statement. I have read explanations for this but they differ. Some authors say twin(say B) who takes the trip accelerates so he can't be an inertial frame of reference. Some say it has nothing to do with acceleration and...
  28. Ivan Seeking

    Postal Paradox: Risk Mail Theft or Take a Chance of Injury?

    This came up today and is an actual dilemma for me and a lot of other people, apparently. We haven't had problems but a lot of other people have and a friend asked about it. In rural areas especially, mail theft is a big problem at times [as well as mailbox smashing]. Some people opt to put in a...
  29. L

    How does special relativity handle acceleration?

    I'd just like someone to clarify that my argument is correct here. Assume twin A stays on Earth and B goes 2 light years away and then back to Earth at a velocity of 0.8c From Earth frame of reference: Twin A makes the calculation that 2/0.8=2.5 years will be needed for the outward...
  30. D

    Understanding The Twin Paradox

    The twin paradox seems not to be understand by everybody. But if you see it like this (see below), everybody would understand it. Why are we getting older on Earth ? Our (relative) time system is the system we compare time to the axes of the Earth. If we start in 1 point on the surface...
  31. J

    Pinocchio Paradox Can we make an equation out of it?

    The Pinocchio paradox arises when Pinocchio says: "My nose grows will now grow." "The Pinocchio paradox is, in a way, a counter–example to solutions to the Liar that would exclude semantic predicates from an object–language, because ‘is growing’ is not a semantic predicate." - Wikipedia "If...
  32. J

    Portal A & B question (maybe a paradox)

    This question comes from a doubt i had while playing the popular puzzle game Portal. 1-Lets say hypothetically that we have portals, and we can move them around freely. We have portal A & B. When you enter portal A you come out through portal B and vise versa. In the case of being placed...
  33. Y

    Questions regarding a paradox.

    I sit in math class everyday and wonder what would happen if I were to send my pencil, which has been sitting still on my desk for sometime now, back in time so that my future pencil occupies the same space as my past pencil. Obviously this is a paradox because if the pencils annihilate each...
  34. A

    Twin Paradox: Accelerating, Turning Back & Decelerating

    hi... In the twin paradox, we consider that one of the twins went out of the surface of Earth ACCELERATING , then suddenly TURNED BACK and then DECELERATED back towards the Earth with some relativistic velocity………. Why is it so? What if the twin goes on a round trip around the Earth and...
  35. Y

    Twins Paradox: The paradox within the paradox

    The twin who has left Earth and travels close to the speed of light in his spaceship, lands back on Earth only to find everyone has died of old age thousands of years ago. This I'm told is because the perception of time and time itself, within the inertial frame of reference of the spaceship...
  36. W

    Twin Paradox: Who is Older - B or C?

    Lets say we have triplets on Earth A B and C. B and C goes from Earth together in the same direction at some relativistic speed let's say lorentz factor one milion. Now after one year passes from the point of A, brother B decides to stop. Now after one more year from the point of A passes...
  37. A

    Solving the Assassin Paradox: A Q&A with Adrian

    Hi all, I've heard it said that if I could send a message faster than light, then another inertial observer would think it was going back in time. If the message was to hire an assassin to kill me before I sent the message, we'd have a paradox. I'd like to understand the details of this...
  38. A

    IBP Paradox for cot x integral

    Greetings! I hope this is the correct forum for my question (this is my first post, here). The problem statement Find: \displaystyle\int \cot x \ \mathrm{d}x A Solution We can re-write this integral into a convenient form: \displaystyle\int \cot x \ \mathrm{d}x = \displaystyle\int...
  39. J

    Solve Obler's Paradox: Calculate Universe Size in Parsecs & Light Years

    ρHomework Statement Suppose all stars had the same radius as the Sun, and they were distributed throughout the universe with the same density as we have nearby- about 1 star per cubic parsec. Approximatly how bigh in parsecs and light years would the universe have to be in order to avoid...
  40. phinds

    How does the twin paradox work in a circular orbit?

    There have been a couple of posts over the last few months that posit a relativistic-speed path in a circle around the Earth and I want to make sure I correctly understand the ramifications. It's the twin paradox in a circle. SO ... here's a scenario that I think will solidify it for me: This...
  41. P

    How does the Twin Paradox demonstrate the effects of general relativity?

    Here is an explanations due to Daniel F. Styer, Prof Physics at Oberlin Daniel's original is at https://mail.google.com/mail/?ui=2&view=bsp&ver=ohhl4rw8mbn4". He uses general relativity and the equivalence principle. The equivalence principle is not entirely true -- it IS possible to...
  42. J

    Twin Paradox Explanation Needed

    So in the twin paradox, the traveling twin ages less in the end. According to time dilation, each twin sees time passing in the other twin's frame of reference slower than his own. However, if the twin on Earth is ultimately older, doesn't time have to appear to be moving faster for the twin...
  43. G

    Triplet paradox: where's the error in my logic?

    Consider the following scenario: There is a triplet of persons A, B and C. Person A stays on earth, while person B and C both go onto two different space missions, the directions parallel to each other. Person B travels at 0.45*c, person C at 0.9*c. The space missions are both set to take...
  44. Demystifier

    Ballentine on the quantum Zeno paradox

    I know that many people here have a very high opinion on the Ballentine's QM textbook. I am also one of them, but one particular subsection of it is (in my opinion) wrong. This is the subsection on the quantum Zeno paradox, or as Ballentine calls it, the "watched pot" paradox in Section 12.2...
  45. P

    Twin paradox: who decided who is the younger one

    Hello, Still puzzled about the twin paradox (one guy stays on the ground, the other goes travelling). If we see the two twins as points in 3D space, the only thing that changes, is the distance between two. That is, the two guys are in totally symmetrical positions, and there should be no...
  46. P

    Can two stationary electrons generate a magnetic field?

    Suppose there are two electrons which are not moving relative to each other. Then in the reference frame of either electron, there is an electrostatic force pushing the two electrons apart, and they will move apart. However, if an observer is in a reference frame moving relative to the...
  47. U

    What would Fermi say now about his 'paradox'?

    When Fermi was asked if he believed in the existence of E.T.s he replied "where are they?" and I think the idea was that if there were E.T.s they should have colonized the galaxy by now. What I am curious about is ... given the fact that the ability to detect earth-like worlds with signatures of...
  48. B

    What are the conditions for non-integer exponents to be single valued?

    Nothing much, I have this: I have studied (myself) about this for many days. And I believe that, for some conditions for a complex ψ,ϕ What are those conditions I mentioned about? And which field of study I should go to see?
  49. L

    Question on The Dichotomy Paradox

    Okay, I didn't really know where to post this, but whenever I hear about this paradox it is in a conversation relating to physics. Anyway, for those that don't know the paradox, it states that to get to point 'B', one must get halfway there before they can be all the way there. And to get...
  50. A

    Light travel paradox? Please, help to figure it out

    I need your help to figure it out if the following thought experiment makes sense. Imagine two points in space at the same distance from Earth, 100 light years. At one point a previously unknown supernova explodes; we observe it’s bright light in the sky for several months, and after that it...
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