mollwollfumble said:
JTQ said:
So my thought is simply this – what I’m experiencing right now in this very second, is it always going to be at the same time as someone else is experiencing time? Or could my “right now” be someone else’s past or future?
Your “right now” is never the same as anybody else’s “right now”.
Special relativity tells us this. To put it another way “there is no such ting as simultaneously” in special relativity.
To be more precise, suppose that one observer measures two events as occurring at the same time, then no other observer travelling at a different speed will observe the two events as occurring at the same time. Given that the probability that two observers have the same speed is negligibly small, there is no such thing as simultaneity.
For a more advanced example, with an accelerated observed see https://commons.wikimedia.org/wiki/File:TwentyFiveZones.png
The lines on this chart are “isochrons”, lines of constant time.
Radar-separation hypersurfaces for an accelerated traveler, defined as the average proper-time of sending/receiving a light signal to/from an event i.e. τevent = (τsend+τreceive)/2. Using the axis-labeled units, this is basically a one-gee (~1) constant proper-acceleration round-trip which takes 4 traveler years to complete.
Four purple dots mark engine on/off events as well as the two mid-voyage points at which the direction of acceleration is reversed. Null trajectories extending forward and back from these points define twenty-five separate event-regions in space-time.
These zones (marked off by faint dotted lines) have blue radar-isochrons, and radar-distance grid-lines, drawn in to characterize for events from the accelerated traveler perspective. Separations in this case are at intervals of 0.2 (years or light-years) from the traveler’s radar-perspective.
The two vertical dashed lines (brown) represent the world lines of home and destination sites that are stationary in the x-ct coordinate system here. Following the separation between start and return isochrons into the flat-space region to the right will allow you to measure the triptime elapsed on the traveler’s clocks using the ct-axis calibration here.
