Paradox Definition and 1000 Threads

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...

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...

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

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...

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...

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...

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...

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...

Consider the classical double slit experiment where we are shooting electrons trough a double slit and then capture them on a photographic plate. We know that the pattern of electrons on the plate will differ depending on the state of knowledge of the observer. If he make a measurement to find...

This may be a stupid question, but I am reviewing for the physics gre and can't help but see the zeeman effect and stern-gerlach experiments as contradictions. In the Zeeman effect, a neutral atom energy level will split into 3 levels (or 2 or more if take into account anomalous zeeman), but in...

I tried searching it up but the only good place i found was wikipedia that actually talked about it and i hate wikipedia because it tries to explain complex things in complex ways instead of making them simple. Thanks!

So, I have an idea to write a (sort of) "time travel" story in which future historians are able to transport a non-intrusive (possibly mass-less) viewport to various important events in history (and then accidentally incinerate Mohenjo-Daro with this technology, thus explaining certain Vedic...

Hello, This is the thread I originally wanted to respond to, but it's closed: https://www.physicsforums.com/showthread.php?t=650126 I also found this on Wiki-talk page, which seems to be the same argument...

I have already read about the twins paradox a lot of times, but what puzzles me is that how the Universe would "now" what twin had to be younger since, if the spaceship travels at high speed in relation to Earth, the planet would move the same with the ship as reference.

Did gravity effect the suns output? arXiv:1405.4369 [pdf, ps, other] Can a variable gravitational constant resolve the Faint Young Sun Paradox ? Varun Sahni, Yuri Shtanov Comments: 9 pages, 1 figure Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Cosmology and Nongalactic...

Hi I'm wondering: The symbol of charge is Q but the SI unit of charge is coulumb which is the Charge of approximately 6.241×1018 electrons. But charge is not itself defined, only in terms of Coulomb, and coulomb is defined in termes of Charge. Its SI definition of Coulomb is the charge...

Here is my understanding, please correct me if I made any mistake Quantum physics theory suggests that information (the wave function, state, etc.) cannot be destroyed. All matters fall into a black hole will not be able to escape, which means all information of these particles stay inside...

Hi! I have been pondering a scenario involving a paradox with length contraction. I brought it up with my physics professor, and I somewhat understand what is supposed to happen, but I'm still somewhat confused, so I was wondering if you could help me figure out what is going on. In this...

If we suppose we have an entangled pair in position/momentum and, following the argument, we measure position of particle A. We get a result let say xA. Then we want to predict the measurement of position of B, so up to now we have not measured particle B, but we know it's wave-function is a...

Hi, from what I understand about the twin paradox, Is the resolution essentially that since the traveling twin undergoes acceleration when the ship reverses direction, so since the velocity of the twin is no longer constant, the inertial reference frames are no longer valid? Then does that also...

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. You can't. This is simply because...

If three circular or ring type magnets are placed such tnat centeral magnet is having its center at origin and other two are placed at its aperture repeling each other but they are just at enough distance such that the whole system is in equillibrium, placed on surface having friction. If i...

Hi all! I was reading up on the Klein paradox in Itzykson & Zuber's Quantum Field Theory (but I think this is a pretty standard part that's probably present in most QFT textbooks) and on page 62 they have a pretty straight forward solution to the Dirac equation with a step potential. I've...

I have read Max Tegmark's book "The Mathematical Universe" and he describes this thing called The Measure Problem as the biggest problems in physics. I am having difficulty understanding the problem so I will try to sum up my understanding of what he said. As a result of inflation, the volume...

Consider the following setup (see illustration above): a mass m is connected to a circular section of a rail by means of a rod (with negligible mass) of length r, where r is the radius of the rail. The connection point P of the rod can move frictionless along the rail but is mounted such that...

Consider two points A and B (Fig.1) at rest in S frame having a distance L0 between them (a long scale may be imagined as placed between A and B). ------ (1) The ‘traveler’ twin (S-frame) starts from A at time t = 0 and suddenly accelerates to attain a constant velocity v in the view...

Relativistic compressor "paradox" Let's say we have a metro tunnel that is a circular loop with 1 m x 1 m rectangular cross section. The tunnel is 100 m long. There's a 50 m long train in the tunnel, the train fits snuggly in the tunnel. And there's air in the tunnel, at 1 atm pressure, and...

Traveling signal “paradox” Most relativity paradoxes are not true paradoxes they merely require some clarification about frame of references, stationary observer, etc… I hope some folk could help me clarify my “paradox” or point out where someone as already discussed this concept. We...

A student asked me a question in class last week about the twin paradox, and I found that although I knew a valid answer, it wasn't an answer that my class had the background to understand, and I wasn't immediately able to come up with one that would work for them. The standard difficulty in...

Hello all This is probably simple and I'm overlooking something 1 mile = 5280 feet 10% of a mile is 528 feet 528 feet squared is 278,784 feet which is 52.8 miles squared But 0.1 miles squared is .01 miles squared So depending on if you square it as 0.1 miles, or if you convert...

I'm sticking my neck out because I just worked this out and may regret this post later. The spaceship paradox arises because the expansion scalar of the 'Bell' congruence is always positive, implying that the thread will break, even when the ships are not separating. For this vector field...

Suppose Alcubierre warp drives or some alternative form of warp drive is possible. Then surely a warp drive could enter the event horizon of a black hole, observe the interior, and exit the horizon, returning with information from within the black hole. What about black holes never visited by a...

It is said that Relativity proves that if one travels near the speed of light that time slows down, i.e. that the twin who travels ages less than the twin who stays behind (Twin Paradox) and that distances/lengths contract, but only in the direction of travel. Yet a simple look at these two...

I'm sure there must be some explanation to why these kind of things appear.. firstly, consider a=b ab=b2 a2-ab=a2-b2 a(a-b)=(a+b)(a-b) a=a+b since a=b, b=b+b 1=2 !?? then this one- (100-100)/(100-100) =[(10+10)(10-10)/10(10-10)] =2 Anything has gone wrong?

This blog post https://medium.com/starts-with-a-bang/df0a131d7b95 by Ethan Siegal claims that the firewall paradox is resolved. The papers it refers to are: Samuel L. Braunstein, Stefano Pirandola, Karol Życzkowski, "Better Late than Never: Information Retrieval from Black Holes,"...

Would it be possible for a black hole to carve a trail of information on two dimensional space in the holographic universe? Could the black hole, acting as a conduit between the macro and micro universe, due to its properties at the singularity (at the plank scale) carve the the information...

Hey guys, I just want to ask a quick question that confuses me a bit regarding the twin paradox. During acceleration, the moving twin very quickly 'runs over' across a large segment of the worldtube of the stationary twin. But, what is the perspective of the stationary twin during the...

Hi, I noticed this topic already being discussed but didn't want to hijack the thread with a different question. I don't know if this has been asked before but if it has I couldn't find it. I was watching something recently about quantum physics and entanglement and it mentioned something...

Here is an ultra short repeat of the Zeno Paradox, but please google it for a longer version with pictures etc: Think of a moving arrow. In an instant of time an arrow cannot move (bc its an *instant*). An arrow's movement is given by the sum of the movements at every instant. But since in...

Consider a solid sphere and a cube of equal mass, both on a frictionless table. Now, you apply a force to both objects at the point of contact between the object and the table. Then the linear accelerations of both objects will be the same (since the same force is applied to the two objects of...

Two twins A and (evil) B. Twin A remains "stationary" while evil B goes at near light speed to-and-fro. Ignoring General Relativity (acceleration/deceleration) evil B experiences time dilation and as result, when they meet up again, B's clock is behind A's clock. Look at it from B's point...

The most famous time traveling paradox is the Grandfather Paradox, where the traveler goes back in time to kill his own grandfather and thus prevents his own birth--a paradox. An adaptation to this paradox is Hawking's Mad Scientist Paradox where a mad scientist opens up a wormhole one minute...

Hello, I've read through several sources about the EPR Paradox but I'm not sure I'm understanding everything. I know that: -the paradox in question seems to be due to a violation of the principle of locality -there is no useful transferred faster than c regardless of which axes the two...

I've asked this question a few times. This time i have tiny change in the question. Instead of people I'm using stopwatch & i have removed the accelerative frame. If you have any doubts I'll clear it but do not skip the topic. All i want is an answer that can be agreeable for all...

As I understand the ZFC solution to Russell's paradox, since {x|x\notinx} must be {x|x\notinx}\capS for some set S, the paradox goes away, but in Morse-Kelley, if I understand Class Comprehension correctly, although again there must be some M such that {x|x\notinx}\capM, this M may be a proper...

Suppose we consider the spin 1/2 measurement matrices B=\frac{1}{\sqrt{2}}\left(\begin{array}{cc} 1 & 1\\1&-1\end{array}\right) and A=diag(1,-1) it's easy to show that B^2=A and a normalized eigenstate of B |\Psi\rangle=\left(\begin{array}{c}a\\b\end{array}\right) with eigenvalue 1 ...

Hello! I am currently learning the theory of relativity, but have a hard time understanding the time dilation concept. In my example down here, the subscript “A” will be used to denote “in the frame of reference of observer A”; the subscript “B” will be used to denote “in the frame of...

First of all, Happy Thanksgiving to you all! Now, my question: I'm on Earth viewing through a telescope. I observe a car in outer space, traveling roughly at right angles to me (i.e., across my scope's field of view, let's say left to right). That car, a 1956 Chevy (irrelevant, but my...

<<Unacceptable Link>> Why in C's FOR object doesn't fit?

Hi, As is well known, Relativity claims that a rod of a given proper length will appear length contracted when measured by a moving observer. Now consider a rod of length L and observer initially at rest relatively to it, with one end of the rod at the observer's coordinate x1(0) and the...