Simultaneity Definition and 298 Threads

Context, To start with? You all know the original twin paradox. Quick review so nobody is confused : Original Twin Paradox: Traveling twin travels at v=0.8c out 4 light years (5 earth years pass)and then he returns home. Earth twin ages 10 years and traveling twin ages 6 because the...

This has probably been discussed/explained many times before so I apologize in advance. Please just direct me to the relevant thread if it has. In Morin, "Special Relativity For the Enthusiastic Beginner", he explains the loss of simultaneity and specifically the "rear clock ahead" effect. If...

Hello everyone, So I think maybe what confused me with the symmetry of time dilation was not understanding relativity of simultaneity. After looking into it if you have two clocks P and Q that synchronize when they meet and if ##\gamma## is 2 then from P's reference frame P equaling 10 and Q...

I want to construct an experiment similar to that described by Einstein in his thought experiment: https://en.wikisource.org/wiki/Relativity:_The_Special_and_General_Theory/Part_I#Section_9_-_The_Relativity_of_Simultaneity How would I design it to ensure the light from the flashes at the back...

When two remote events are observed/measured to be simultaneous in one inertial frame, the same events will not be simultaneous when observed from a second frame in uniform motion relative to the first. Why is this distinction in the kinematics of light not considered an operational distinction...

I know very little about quantum physics. I was looking up the definition of quantum entanglement and asked ChatGPT to explain it. Here is an interesting phrase in its answer: "Once the particles are entangled, measurements made on one of the particles will instantaneously affect the state of...

In his thought experiment on the relativity of simultaneity, Einstein synchronizes two clocks A and B (at either end of a rod) to the clock C in a stationary frame, while A and B (the rod) is moving relative to C. The equations Einstein finishes with demonstrate how observers moving with A and...

As a layman in physics, I cannot understand the block universe concept followed by Rietdijk-Putnam-Penrose Argument. Let me clarify my question as follows: Suppose two objects, one stationary and one moving towards the other one at constant relativistic speed, e.g. 05.c and let's also presume...

Hi all, I have been figuring out relativity. I was just wondering how meaningful the simultaneity convention is, how meaningful it is for say something a million light years away to be on our plane of simultaneity. I'm guessing not very, we must really wait for light to get to use to have...

I have not seen this exact configuration discussed. Observer A in middle of train. Observer B at station. Both A and B think the other is moving. Observer A synchronizes two clocks and puts one at each end of train. Lightning strikes both clocks stopping them when A passes B. B says...

Hello. I'm new here and very much afraid of breaking rules. I would gladly post this question in the Homework section, because it's homework, but my question doesn't fit the template, it's a theory question. I hoped to find it in Relativity FAQ's, but it's not there. I can tell you I grasped...

This is not a homework question, just a scenario I've come up with. Imagine I have a male and a female clock moving towards each other. If they're in sync, one will fit inside the other and they'll continue on their way. If not, they'll collide. (Apologies for the crude drawings.) I place these...

0:00 What is spacetime? 20:20 Kinematics, basic definitions 35:18 Motion of test particles 41:18 Frequency shift of light 1:10:19 Simultaneity

Hi, reading this old thread Second postulate of SR quiz question I'd like to ask for a clarification on the following: Here the Einstein definition of simultaneity to a given event on the Langevin observer's worldline locally means take the events on the 3D spacelike orthogonal complement to...

<Moderators note: split from https://www.physicsforums.com/threads/is-the-relativity-of-simultaneity-more-than-just-a-fudge-factor.1012027/#post-6596771 > I have a (probably) stupid question. My rest frame contains myself and the usual rigid 3D array of clocks. I use Einstein's method to...

<Moderator’s note: a reference to an article published in a predatory journal has been removed. References on PF should be from the professional scientific literature or from other sources consistent with the professional scientific literature> I read through many posting on various threads in...

Hi, I´m trying to solve a special relativity problem, and I think I need some help. There are two inertial frames of reference, ##O## and ##O'##, the last one moving with relative velocity ##v## in the ##x## direction. There's a rod with length ##L'## fixed to frame ##O'##, such that front end...

This thread, some earlier ones, and my signature got me thinking a bit about whether it would be a good idea to de-emphasize simultaneity when teaching SR since it is a frame dependent concept. I did not do much thinking myself yet but would like to hear people’s opinions and thoughts on how...

Hello, Hope you had a merry Christmas, :wink: In order to deepen some knowledge on the notion of relative simultaneity, I studied a graph taken from a video, and the ages of the twins being very very rounded, I decided to make precise calculations using two methods different. I would like to...

Hi, searching on PF I found this old post Global simultaneity surfaces. I read the book "General Relativity for Mathematicians"- Sachs and Wu section 2.3 - Reference frames (see the page attached). They define a congruence of worldlines as 'proper time synchronizable' iff there exist a...

Posed question is that a comment plunges into Jupiter. Same time as my physics class starts on Earth. My friend is traveling towards Jupiter at a significant percentage of c. Would the person in spaceship say that the comment collision occurred before, after or as class started? My answer: same...

I made an exercise whose question is like that: A spacecraft moves with speed v at the axis x. There are two target at the axis x, in which the distance between them is L at the ground frame. Suppose that the spacecraft shoot the target simultaneously when it passes by the target. A|so...

Let us set up a very simple circuit, with two resistors in series as shown in the sketch. We know that for this particular circuit ##V_{14} = V_{12} + V_{23}##. But what I have always wondered is: How does the circuit "know" that once I introduce a battery of ##8 V## that each of the bulbs...

(excuse me for my english, but I'm studying physics and I am not a native English speaker) One observer OE, is on the ground, we take him as the fixed frame of reference. The other OT is on the train that is moving relatively to the OE at a costant velocity ( they are both inertial frame of...

Hi All, I've been doing some reading on the above but having some problems understanding certain parts of it (maybe it's wrong from Wikipedia!) To simplify it for me I will first pose a simple scenario where we are not factoring in speed yet, then go from there. Say we have two planets A and B...

What is the advantage of considering the generalised simultaneity criterion ##t = (1-\epsilon)t_1 + \epsilon t_2## for ##\epsilon## between ##0## and ##1##? How does varying the parameter ##\epsilon## help to elucidate the structure of the special theory? I think the surfaces of simultaneity are...

(I hope my English is understood). Hello, I have a question regarding the relativity of simultaneity. The mean temperature of the cosmic microwave background tells us how big the universe is with respect to the recombination epoch. If I now measure that the mean temperature of the cosmic...

What is my first step here? I'm not sure of where to start?

In special relativity, observers can disagree on the order of events - if Alice thinks events A, B and C are simultaneous, Bob can think A happened before B which happened before C, and Carlos thinks C happened before B which happened before A - provided A, B and C are not causally connected, of...

The question is in reference to calculating relativity of simultaneity. I am on the step where I take the time in Alice's frame from the front and from the rear clock and minus it to the get the total time. I end up with gamma squared etc (For more details see the picture below) I have...

I've been slowly grinding away with what I can about quantum mechanics and QFT. I'm not sure how far I've gotten but I've come up against a bit of a roadblock concerning how the relativity of simultaneity applies in QFT with specific reference to the outcome of Bell tests. My misunderstanding...

I'm reading about how the concept of simultaneity breaks down in special relativity. Here's the relevant paragraph: ----- Consider a photon source ##C_0## in a train car situated equidistant between detectors ##C_1## and ##C_2##. The source emits photons back to back. In a reference frame at...

Suppose there is a beam balanced on a fulcrum at its center of mass. One observer at rest with respect to the beam sees two lightning bolts strike the ends of the beam simultaneously, such that there is no net rotation of the beam. However, a moving inertial observer sees one bolt strike one...

Something that I consider very silly, yet I try to solve relates to the relativity of simultaneity. According to SR , two evevnts taking place in different positions along the line of relative motion of two inertial observers are not simultaneous in both frames. Now, I wanted to see how this...

The famous example demonstrating that simultaneity is an non-invariant variable would be the lighting bolts striking a fast moving train. Or a projector at a mid-point shooting off two beams at the same time to receivers on the opposite ends (for the person at rest and not on the train's...

Suppose we have two observers A and B and they are at rest. Observer A observes two objects falling from height H (A has same distance between the two objects). Does observer B will measure different times for the duration of falling of the two objects ? (because the two object are not in the...

I am studying the fact that two events that are simultaneous in a frame aren't (in general) simultaneous in another. The lamp is equidistant from the two ends. When the light is switched on an observer on the train sees how both light rays hit the back and the front of the train...

Question from non-physicist. Hope there is a simple answer. In Einstein's thought experiment with moving train and embankment: If there is an observer in the middle of one of the train cars and one light beam is flashed from inside each side of the car (same location on each sides) towards the...

[Moderator's note: Spin off from previous thread: https://www.physicsforums.com/threads/is-the-andromeda-paradox-accepted-in-physics.960861/] There's just one thing I don't understand about all this, Einstein's train thought experiment. It basically states that an observer in a train moving...

In Classical Mechanics, according to SR, the concept of simultaneity is dead, a meaningless concept. But in QM, entanglement implies that some limited form of simultaneity exists. If we have two particles correlated due to entanglement, a measurement of one particle immediately gives us the...

Hi guys, I've been asked to check somebody's relativity logic and i'd love to get s second opinion as it's easy to slip up. There is a train, with an observer (A) in the middle, with a device that fires marbles simultaneously up the train and down the train. There is also a...

Here is a diagram from the Wikipedia. I'm sure you understand what this represents. Those who don't, can go to the Wikipedia page (https://en.wikipedia.org/wiki/Twin_paradox) and see all the details. After my prior post, I have a better appreciation for simultaneity. Originally, when I looked...

Hello I'm having a lot of trouble understanding simultinaity and would appreciate any free book or article reccomendations.

Hello I am investigating a thought experiment conducted by Einstein in which he imagines a man on a train platform (it is being explained on a documentary I am watching). Two lightning bolts equidistant from him strike at either side. He sees these bolts of lighting strike at the same time. A...

Imagine you are in the center of a ship moving at V to the right relative to earth. You have a flashlight in your hand and two perfect reflectors on each end of the ship. If you turn on the flashlight will you observe the reflected light from both ends to hit you simultaneously? What will...

Homework Statement A thin rod of proper length 4a is traveling along the x-axis of a frame S with a speed ##{\frac {\sqrt 3} 2}c## in the positive x-direction. A hollow cylinder CD of proper length 2a is placed with its axis along the x-axis, so that when the ends of the cylinder are open the...

I always liked the idea of starting relativity discussions with the idea that your father could travel at a substantial fraction of the speed of light and return back at roughly the same age as you. This makes time dilation seem interesting, and drives curiosity in students. But I'm struggling...

For an inertial frame in flat spacetime with cartesian coordinates, and a particle in that frame whose worldline is a helix (moving in a circle at constant speed in x-y plane), given an arbitrary event with coordinates ##t##, ##x##, and ##y##, (we won’t worry about ##z##) how would I go about...

Hi everyone, I'm struggling to grasp simultaneity in Special Relativity. Since I am struggling conceptually, I have posted my question here. But if you think this problem I made up modified should go to homework, I apologise (and feel free to move it). Suppose we have two light sources...

Hello, Is anyone familiar with the French Standard DTU for water supply infrastructure networks. I'm not understanding how to apply the diversity factors and coefficient of simultaneity to calculate the instantaneous maxumum demand and where to apply it. I was thinking of applying the formula...