Spacetime
Spacetime Mechanics
3D Diagrams
Zero Intervals
Proper Time
The Two Towers
Spacetime & Reality
Spacetime & Reality
The model of space and time as a four dimensional continuum, spacetime, is fundamental to Einstein's relativity, and has been very successful.
Furthermore, the fact that spacetime intervals are frame invariant seems to offer a more coherent picture of space and time than the frame dependent coordinate distances and time intervals.
There seems to be a growing belief that spacetime is real, particularly amongst people who are interested in relativity from a philosophic standpoint. So it is important to consider whether spacetime is real both in a scientific and a metaphysical sense, or whether coordinate space and time more closely correlate to what actually takes place. In this respect, spacetime is not without issues:
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We note here that the property of spacetime whereby time intervals and spatial distances cancel does not seem to match how macro objects experience space and time.
- We note here that proper time only correlates to the actual time passing when it coincides with the coordinate time lapse.
However, perhaps this issue is most clearly described in the Twin Paradox. In this thought experiment, differences in the passage of time arise, which correlate to differences in the coordinate time lapse in the respective frames of reference.
Furthermore, this effect is not just theoretical. There is plenty of empirical evidence that the actual passage of time is slowed down for an object which has been accelerated to a high velocity, compared to an object which has remained un-accelerated. Indeed, differences in the time lapse are compensated for in global positioning satellites. These actual time diferences correlate to the coordinate time lapse (in the respective frames of reference), not the spacetime interval.
So there is strong evidence that coordinate time intervals are real. Hence the spacetime intervals may be no more than mathematical abstractions.
