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. D

    Simultaneous Paradox Explained - 65 Characters

    see the attachment referring to the pic 1 simultaneity was explained to me like this there is a moving box car. At point A there is an observer in the boxcar at rest wrt the box car his name is Dash. There is another observer not at rest wrt the box car at point C his name is Still...
  2. S

    Feynman's apparent paradox - Electromagnetism

    Feynman's "apparent" paradox - Electromagnetism This is the paradox discussed in chapter 17 of "Feynman Lectures on Physics - Vol II" http://www.flickr.com/photos/37453425@N07/3447068420/ Say suppose the battery drains out or somehow you stop the current outta the battery. By...
  3. B

    Twin Paradox in outgoing frame

    Homework Statement Show that as calculated in the rest frame comoving with the twin on the outgoing trip, the ratio of the two ages of the twins is the same: i.e. the twin on Earth has age gamme times the other twin Homework Equations Lorentz Transforms The Attempt at a Solution We...
  4. M

    Minkowski/Twin Paradox: Examining an Objection to STR

    2. Consider the following objection to STR: “Since time-dilation and length-contraction are reciprocal, STR actually contradicts the frame-invariance of physical age differences, that is, the plain physical facts. For instance, so there can be no ambiguity about “age comparisons”, let us replace...
  5. T

    Modificaition in pole and barn paradox

    In the pole and barn paradox, if the observer (person A) closes the both doors simultaneusly (with respect to himself), when he sees the runner's stick (person B) is just inside and keeps it closed forever after that, how will things happen, will the runner be traped or the door will hit the...
  6. K

    Understanding Einstein's Paradox: The Answer Revealed

    an atom goes through a particular nuclear reaction and emits a left-handed and right-handed particle. after the particles have traveled to opposite sides of the universe, if you measure the handedness of one you instantly know the other's which is information moving faster than the speed of...
  7. T

    Twin Paradox: Explaining the Relativity of Aging

    I know very little about relativity. I have heard that it implies that----- if A and B be two tweens. If A goes in a space trip and then return to B at earth, he will be younger than B. What I am confused is, It must be same thing whether A went away from B in his space trip on the ship or...
  8. rjbeery

    Exploring the EPR Paradox: Reconciling QM and SR

    Greetings! This is my first post so go easy. I read through the thread addressing the Sci Am article claiming that entanglement violates relativity. The article actually addresses a symptom of a larger issue that exists between QM and SR. I would like to get feedback on this issue as...
  9. G

    Does life present any information paradox?

    This question might rather be posted in Biology but since the information paradox is usually the subject of black hole physics I thought physicists may be better placed to answer it. The fact that information may be lost in black holes is considered a paradox, information is believed to be...
  10. P

    Kinetic Energy Paradox: Physics Community Discussion

    Hello Physics Forums, I am new here and I thank the community for any input I might receive on my physics paradox. To some of you this may not be a paradox and I hope that you may be able to explain to me how this makes sense from all reference points. The paradox follows as such: It has...
  11. K

    The Big Rock Paradox: Stephen Hawking's Thought-Experiment

    I was first introduced to this thought-experiment upon reading Stephen Hawking's A Brief History of Time . Suppose an omnipotent being exists. If it does, it would be able to do anything (by definition!). Therefore, it would be able to produce a rock it couldn't lift. Therefore, it wouldn't be...
  12. T

    My Sad Paradox: Watching 30 Years in 3?

    this is my 1st post, and its a question that i had developed, most likely out of ignorance, so please save me from my sad paradox. lol Thank you, in advanced. I understand if i where floating in the bulk of space with no visual queues to give me aid in telling me if I were moving, i could...
  13. A

    How Does Zeno's Paradox Challenge Classical Mechanics?

    Please take a look on this paradox. http://knol.google.com/k/alex-belov/paradox-in-classical-mechanic/1xmqm1l0s4ys/3# What do you think?
  14. A

    Consequences of Hardy's paradox and joint weak measurement

    I read two articles recently and I am wondering if I have the correct interpretation of them. They deal with joint weak measurement and Hardy's paradox. Is the result of the "Direct observation of Hardy's paradox by joint weak measurement with an entangled photon pair" paper indicating...
  15. C

    The Twin Paradox: Exploring Age Difference & Time Travel

    The idea is as follows: My (imaginary) twin and I were born at the same time, thus just as old. Now, my twin made his own spaceship in the backyard, one day, and decided to go for a ride. It had only room for one person, so I had to stay behind. Now, my twin went out of the Solar System and...
  16. N

    Paradox Regarding Hermiticity

    Here is an interesting piece of paradox. We all know Hamiltonian is an energy operator in Quantum Mechanics.The Schrodinger's equation tells that \ H\psi=\ i \hbar\frac{\partial}{\partial\ t}\psi Now,we also know that Hamiltoian is Hermitian.But are we sure that \ i...
  17. J

    Sun's Corona Paradox: Temperature Defying Laws of Thermodynamics

    Why is the sun's corona temperature around millions of degrees celsius while the sun's surface is about 6000 degrees celsius? Doesn't that defies the laws of thermodynamics?
  18. C

    Is Electromagnetism Relative and Does it Create a Paradox in Moving Frames?

    Correct me if I am wrong, but, if electromagnetism is relative then in a frame where charges have relative motion between the observer, the observer would detect electromagnetic radiation being emitted from the charge, and that to an observer moving alongside the charge at the same speed, no...
  19. C

    Unraveling Hardy's Paradox: An Analysis of the Controversial Theory

    http://arxiv.org/abs/0902.3376"
  20. malawi_glenn

    The Gamma Matrix Trace Paradox: A Conundrum in Spinor Calculations

    gamma matrix trace Paradox?? Hello, i tried to evaluate this particular little guy: \text{Tr} (\gamma ^0 p_\mu \gamma ^\mu \gamma ^0 q_\nu \gamma ^\nu ) using these identities: \gamma^0 \gamma^0 = I \text{Tr} (\gamma^\mu \gamma^\nu \gamma^\rho \gamma^\sigma) = 4 (g^{\rho \sigma} g^{\mu \nu}...
  21. C

    Russell's Paradox: Understanding the Contradiction of Sets

    I understand how the argument goes- let X be the set of all sets which don't contain themselves. If X contains itself, then X is not in X If X doesn't contain itself, then X is X the part i don't understand is, What on Earth does it mean for a set to contain itself? garbage in, garbage...
  22. M

    Paradox? An infinite set having finite volume?

    Paradox? An infinite set having finite volume?? Homework Statement Find the volume, in terms of k, of the solid made from R rotating about the y-axis, if R is defined as the region bounded by e^{-x} and the coordinate axes. 2. The attempt at a solution Obviously, \displaystyle\int^{1}_{0}...
  23. 3

    Can You Be Both Dead and Alive When Traveling at Light Speed?

    I'm new, and basically just study physics as a hobby. I've yet to understand the mathematics, just the concepts. In studying spacetime contraction, I led myself to a paradox, which would leave someone both dead and alive. Let me explain. Say you were on a spaceship that could travel at light...
  24. J

    Zeno's Paradox (Quantum Level)

    Hello Everyone, This is my first post, I didnt see an introduction section to give some of my background. Let me know if there is one somewhere? Anyway, Years ago, I attended a lecture on Zeno's paradox. The paradox basicly says," how many times can I ask you to walk halfway to the...
  25. D

    Twin Paradox with acceleration

    Homework Statement Assume a rocket ship leaves the Earth in the year 2100. Castor, one of a set of identical twins born in 2080, remains on Earth to work at Mission Control, while the other twin, Pollux, travels in the rocket. Ignore the motion of the Earth relative to the fixed stars. The...
  26. A

    Exploring the Paradox of Amelino-Camelia's DSR

    Is there not an inherent paradox in Amelino-Camelia’s DSR (Doubly special relativity)? Every solid piece of matter is the sum of its parts. Put another way, all the building blocks of a meter stick must be less than a meter in length (e.g. the lines dividing centimeters, millimeters, the...
  27. marcus

    Lundeen Steinberg claim to resolve Hardy paradox

    http://www.physorg.com/news151164690.html Lucien Hardy's QM paradox goes back to 1992 or 1993 when he was a grad student at Durham UK. Lundeen and Steinberg's paper was published in Physical Review Letters January 16. They confirm Hardy's paradox, and offer a theoretical explanation or...
  28. D

    Is E=mc2 Related to Zeno's Paradox?

    If e=mc2 wouldn't that mean I'm in a Xeno's paradox? and What would things be like if e did not equal mc2? ? I understand why it must equal mc2 but can't imagine how things would be if it didn't. and If we watch what's happening in the universe in mega ultra super fast forward wouldn't it...
  29. quasar987

    Russell's paradox, ZF and Gödel's undecidability

    I'll be giving a small talk to the graduate students of my university on the topic of "counter-examples" and my first counter-example is Russell's paradox. I want to put the theorem in context, but admitedly, I have no idea what I'm talking about when it comes to logic and set theory. I want to...
  30. A

    Medical Can Marijuana's Active Ingredient Prevent or Reverse Alzheimer's Disease?

    Marijuana isn't known for being a friend to memory; its short-term effects notoriously impair recall. And although the data is conflicting, some studies link cannabis with memory deficits in those who use excessive doses for long periods of time But new research suggests that one of the active...
  31. M

    Photon energy and momentum paradox

    Homework Statement Find the momentum and energy of photons of light of wavelength 500nm. Usual data of h = 6.63 x 10-34 and c = 3.0 x 108ms-1Homework Equations The Attempt at a Solution > To get momentum, i simply take momentum = h/wavelength = 1.326 x 10-27 kgms-1 > To get energy I use E =...
  32. L

    Understanding the STR Paradox of Electron's Rotating Magnetic Field

    A paradox?...In STR. A thought experiment; This could take place in a hallway or in space, whichever you prefer. Consider an electron somewhere around the center of your monitor. Now have an observer A at the right of your screen closing the distance between the electron and himself in a...
  33. M

    Car & Garage Paradox: Solving the Mystery

    A car (original length 20 feet) is traveling towards a garage of length 10 feet at speed of 0.8c . Now at such high speed length contraction occurs & contraction factor is 2 , so from garage's frame of reference the car has shrunk to 10 feet & it should fit in the garage where as from the car's...
  34. marcus

    New blackhole solution to Einstein eqn, no info paradox (Krzysztof Meissner)

    http://arxiv.org/abs/0901.0640 Horizons and the cosmological constant Krzysztof A. Meissner 6 pages (Submitted on 6 Jan 2009) "A new solution of the Einstein equations for the point mass immersed in the de Sitter Universe is presented. The properties of the metric are very different from both...
  35. quasar987

    How does ZF fixes Russell's paradox?

    In naive set theory, Russell's paradox shows that the "set" S:=\{X:X \in X\} satisfies the weird property S \in S and S\notin S. How does the set theory of Zermelo and Fraenkel get rid of this "paradox"? I.e., which axioms or theorem prohibit S above to be a set? Thank you.
  36. C

    Twin paradox: telling who accelerates (why isn't it arbitrary?)

    I'm sure this question has been asked thousands of times before, but I can't see how nature determines which twin accelerates (or is subject to a gravitational field) and which one doesn't. People say one twin will feel the acceleration and the other won't, but suppose neither twin had an...
  37. P

    Does the Earth's Rotation Affect Time Dilation in Einstein's Twin Paradox?

    I know that the frame of reference determines that it is the stay-at-home twin who ages faster than the twin traveling at some fraction of light speed. Some years back, an experiment in which one of a pair of synchronized atomic clocks was placed on a commercial airliner and flown around the...
  38. C

    Olbers' Paradox, the CMB and the observable universe

    From Olbers' paradox, the night sky is dark because the universe is finite in age, so some stars' light hasn't had time to reach us. BUT, we see the CMB which occurred some 13 billion years ago (14 billion maybe?) So, if light from the cmb has had time to reach us, shouldn't every object's light...
  39. P

    Absorption Paradox: Continuous Photon Energies and Quantized Molecule Energies

    The possible energies of photons is continuous and therefore a photon could have an infinite number of possible numerical values for energy. In contrast all forms of molecular energy are quantized (electronic, rotational, vibrational and translational). Surely the probability of any given photon...
  40. B

    Can a Limo Fit into a Smaller Garage with Special Relativity?

    Homework Statement Carmen has just purchased the world's longest stretch lim, which has proper length 30 m. A garage has a proper length of 6.0 m. Carmen concludes that there is no way to fit the limo into the garage. Her buddy Garageman claims that under the right circumstances the limo...
  41. C

    Exploring the Paradox of Light Traveling at the Speed of Light

    Hi This thought has been in my head for a while and I need to resolve it. If light travels at the speed of light in a vacuum and I am told that it does AND time stops when one is traveling at the speed of light, I am also advised this is true THEN doesn't that mean for light it is...
  42. M

    What is the figure of 6 years representing in resolving the Twin Paradox?

    Resolving the "Twin Paradox" http://mentock.home.mindspring.com/twins.htm I've been trying to follow this unusual explanation to resolve twin paradox, which uses the lorentz relativistic velocity transformation equation to get the speed bob zooms off after Ann at,15/17 C. I can understand...
  43. R

    Paradox of Obtuse Angles in the Sine Rule

    I have read the sine rule: It states--> sin A/a=sin B/b=sin C/c = 1/2R where R is circumradius. Now, a=2Rsin A b=2Rsin B c=2Rsin C For a triangle R is fixed. In an obtuse angled triangle, the side opposite largest angle is the longest(geomtrically) But the sine of an obtuse angle...
  44. P

    Is there a force exerted on both particles in the moving charge paradox?

    Hi there, here I have this paradox and hope you can explain. There are 2 charged particles, one is moving at speed v, one is stationary. We know the moving charge gives off a magnetic field which can not exert any force onto the other charge because it does not move. Now assume we stay in a...
  45. A

    Exploring the Reverse Twin Paradox: Predicting Age Differences at .6c Speeds

    HI My question is what would the outcome be if the twins started out in 2 ships traveling at uniform .6c relative to Earth and one of them then took her ship and traveled to Earth and back? Which twin would be older?
  46. A

    Exploring the Reverse Twins Paradox: A Hypothetical Scenario

    Reverse Twins paradox ? This may have come up before but I haven't seen it and don't know the answer. What if the twins started out in two ships moving together at relativistically significant velocity relative to earth. One of the twins then simply goes to Earth and back while the other...
  47. Artlav

    Twin paradox and the nature of time?

    I'm trying to make sense of the way time dimension is related to the other 3, the example is twin paradox: Observer 1 is moving away at 0.866c from observer 2, who is standing still, then turns around at a defined point and goes back at the same speed, arriving back to observer 2 position...
  48. F

    Solving the Waiting Time Paradox: Uniform Arrivals

    can someone help me with this? if i assume that the passengers arrival is uniform, is it still valid?
  49. T

    What is the resolution to the lighthouse paradox?

    The classic lighthouse thought experiment leads to a situation in which some "thing" is traveling faster than the speed of light. This is the case because the lighthouse's light beam, if powerful enough, will shine a circle of light on its destination that can travel faster than the speed of...
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