# What is Simultaneity of events: Definition and 13 Discussions

In physics, the relativity of simultaneity is the concept that distant simultaneity – whether two spatially separated events occur at the same time – is not absolute, but depends on the observer's reference frame.

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1. ### I Instantaneous coordinates of an event in space (special relativity)

In relativity, no signal travels faster than light, and hence if something happened away from me, I will only know about it after some time. This means I cannot measure instantly the position and time of something as it happens; this would violate special relativity. I however imagine that I...
2. ### B Order of events and cause and effect

I'm reading "Bang!", by Brian May, Patrick Moore and Chris Lintott. On page 40, they say: "So one [observer] may believe A preceded B by a minute, and another that A and B were simultaneous, it is impossible for any observer to see B preceding A. Hence cause and effect are preserved..." But in...
3. ### I Simultaneity of Events: Rest vs Motion

I understand when two observer one at rest wrt Earth and the other in motion wrt earth, two events cannot happen at the same time to both the observer. So, is it, the moment, the observer which was in motion comes to rest wrt earth, would two events now, at once happen at the same time, to both...
4. ### B Einstein's relativity of simultaneity & quantum paradox.

Einstein's relativity of simultaneity & quantum measurement paradox. Suppose a rocket traveling close to the velocity of light which emits a single photon from its midpoint at point A, illustrated below. The rocket is equipped with a single detector drawn in green at the front of the rocket...
5. ### B Relativity of simultaneity and the balance of the systems

Hi everybody, Glad to be with you, in the most popular physics forums on the Internet. First of all, I'm not a physicist and the problem I hope to get the answer from you, is part of the work I'm writing in another field. To cut it short, I don't quite understand how the relativity of...
6. ### I SR Proves Eternalism: Is It Physically Substantial?

Does SR enable the passage of time. Rietdjik(1967)-Putnam(1968)-Penrose-Maxwell and others, claim that SR proves Eternalism. That is; the world is an eternal (a-temporal) 4-dimensional spacetime manifold in which all events exist and the notion of a moving Now (a global hyper-surface of...
7. ### Simultaneity of Events: Understanding Observer Perspectives on Time

Dear PF Forum, What does "at the same time" mean for two observers? I've read https://www.physicsforums.com/threads/criteria-of-simultaneity.699560/. But I want to ask a simpler question. 1. Does "At the same time" mean different for two COMOVING observers than two REST observers? And about this...
8. ### Simultaneity of events inside a singularity

Hello, I was wondering if the following idea had been proposed in one form or another within a scientific community. Provided that the space within the singularity is dimensionless, that being 0 in length on all the axes (is it?) the following is in order. From this follows that the Planck's...
9. ### Simultaneity of Events, Do I Have it Right?

Ok, I want to make sure I understand this correctly. Let's say I'm moving at 90% c and pass a light bulb that is at rest with another light bulb in the distance. In the frame of reference of an observer equidistant from the light bulbs, they flash at the same time that I my distance from each...
10. ### Simultaneity of Events: Is It Possible?

Hi, A friend of mine asked me something about relativistic physics. It's all hypothetical and I told him it's a paradox that cannot be achieved since you cannot go back in time. Here's his assumption: Let's say that you pass through a 'wormhole' to a planet near Alpha Centauri (26...
11. ### Simultaneity of Events in Different Inertial Frames

if two events are simultaneous in an inertial frame, then they would not be simultaneous in another inertial frame as long as they are separated in space.Equally the vice versa is valid.Does this not imply that it would be possible for one to see someone to be born and to be dead at the same time?
12. ### Simultaneity of events in 2 dimensions

Hi all, I am not a physicist. Some engineer friends of mine and I have a question about special relativity in two dimensions. To set it up, there are 2 lights floating in space parallel to the x-axis and a spaceship is traveling at .8c flying parallel to the y-axis towards the midpoint of...
13. ### Spacelike, timelike, relativity and simultaneity of events

Homework Statement Two events, A and B, are separated in space. In one frame of reference, event A occurs first and is seen to cause event B. Is it possible to find other frames of reference where event B occurs before event A? If the order of two events does depend upon the frame of...