Twin paradox Definition and 315 Threads

Hi. I've been struggling with a formulation of the twin paradox in the Kerr metric. Imagine there are two twins at some radius in a Kerr metric. One performs equatorial circular motion whilst the other performs polar circular motion. They separate from one another and the parameters of the...

Homework Statement This is a typical twin paradox problem as laid out in Griffith's Introduction to Electrodynamics, problem 12.16. The problem states that, on their 21st birthday, one of two twins - we'll call her Alice - departs Earth for star X at (4/5)c. Upon arriving at star X, she...

In a previous thread, reference was made to an entertaining "defense" of relativity by Einstein, which can be found here: https://en.wikisource.org/wiki/Dialog_about_Objections_against_the_Theory_of_Relativity One of the arguments Einstein makes in this dialog is that the twin paradox can be...

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...

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...

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...

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...

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...

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...

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?

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

Hey! So the formula for time dilation is: \gamma \Delta t_0 = \Delta t, where ##\Delta t_0## is the time elapsed for a traveller ##S'## who has a relative constant velocity ##u## compared to a stationary observer ##S##, while ##\Delta t## is the time elapsed for the stationary observer...

There is an example for the radio signal for Twin Paradox from the book "Classical Dynamics of Particle and Systems, Thornton, Marion". Refer "1.jpeg", example 14.5, it said that "However, Frank continues to receive a signal every 3 years for the 8 years it takes the last signal Mary sends when...

I was thinking about one of the many resolutions of the so-called 'twin paradox' within SR framework. I realize many methods of resolving this have been proposed, but I am curious about the particular solution that uses 'acceleration' of the traveling twin, to create the required asymmetry for...

Hi Everyone, I've managed to confuse myself with a mutilated thought experiment. A half twin paradox. Imagine a twin, Paul travels away from Earth at 8/10c while peter stays at home. Because of time dilation paul reaches a planet by his clock, in one year. Peter registers Pauls arrival at...

http://en.wikipedia.org/wiki/Twin_paradox I read a little bit about this, and am a little bit confused. I always learned about reference frames. When I jump, you can say that I am moving away from the earth, or the Earth is moving away from me. Why is this any different for near-light travel...

I have make many threads about this topic because I am really interested. I reading that from an pdf,but I have some "idiot" questions too. 1)A guy told me that If you run in other speed from an other you see his clock slower. I have hear about paradox of twins,that this with biggest speed...

The problem statement Suppose the universe is a 2-torus, thus there exists a spatial path that you will go back to where you start eventually. Let Observer A and Observer B travel on this closed path. Observer B is traveling at a constant speed of 0.9c relative to Observer A, where c is the...

Please explain me simply about twin paradox..

now the resolution of the twin paradox as put down in textbooks i have read relies on one observer being accelerated and one not so one can claim to be inertial and thus priveledged - this i always felt to be a cheat - even edward teller uses it in conversations on the dark secrets of physics -...

Disclaimer: I am relatively illiterate on the subject so please try to keep explanations generally understandable. Aerospace undergrad programs get zero exposure to relativity I suppose. [Gravitational Time Dilation] First I want to know if I am correct in saying that the gravitational...

Suppose you have two people who are in identical orbits around a large star. The only difference between them is the direction they are traveling. At a certain point where they meet ( there are two such points ), they sync clocks. After a few orbits, they meet again and again compare clocks...

Hi, my first post on the forums. I've known about twin paradox for a while, so when we learned special relativity at school in September, it wasn't anything weird. Math is elegant, unlike quantum physics. But a few weeks ago, I started wondering something. It might be just an ordinary logical...

I was studying the twin paradox (of Einstein special relativity) and everything was working well until I get to the traveler's spacetime diagram. First let me introduce the paradox for you to understand the diagram. Pam is the twin sister of Joe. Pam goes out Earth in 2007 in a spaceship...

I'm not sure if this belongs here or in Cosmology - possibly either would do, I think. I was reading the thread about open/closed/flat universes that's currently ongoing in Cosmology, and a related question occurred to me. According to post #7 you can have geometrically flat universes that...

i can't get my head around the twin paradox at all. so twins A and B move relative to each other and as a result, according to special relativity, from twin A's perspective twin B will of aged less but from twin B's perspective twin A will of aged less. when they meet up which one will of...

So once again, I'm trying to wrap my head around the asymmetry in the twin paradox problem. Here's my setup. The two twins start on a very massive but small planet such that they always have an unobstructed view of each other. 1. They each attach a beacon to themselves that will briefly flash...

Hi All, I think that I understand (as far as you can!) the ideas behind explaining why two twins have different ages if one travels at near light speed away for a time and then returns to his twin on Earth (the return journey changing the inertial reference frame). I have a related...

What would be the example of the twin paradox where there is no acceleration at all ? Only different periods of constant velocity for both twins. Or of periods with different velocities for both twins.

Hi, I just recently studying special relativity in my class. It's fun and I kind of understand what's going on. But the professor skips the acceleration/deceleration part because it's for advance level. So what happens during the acceleration and deceleration (assuming the object won't get...

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...

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...

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...

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...

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' ?) ...

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...

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...