I Is Spacetime a Real Physical Entity or Merely a Conceptual Framework in Physics?

[Michael Ray Mooney]

Given that physics is the study of the physical world, what exactly is spacetime if it is an actual "real world thing", a curved medium or "fabric" guiding the movements of masses, and what is the physics of how this guidance works. As far as I know, space is a vacuum (where not occupied of course) and time is a human concept designating the duration of any specified movement, like Earth's periods of rotationand orbit. Thanks.

 

[pines-demon]

The physics can be found in general relativity books. Check: Introduction to general relativity for a quick survey.

 

[PeroK]

Given that physics is the study of the physical world, what exactly is spacetime if it is an actual "real world thing", a curved medium or "fabric" guiding the movements of masses, and what is the physics of how this guidance works. As far as I know, space is a vacuum (where not occupied of course) and time is a human concept designating the duration of any specified movement, like Earth's periods of rotationand orbit. Thanks.

Modern physics (since Newton) is generally about finding a mathematical model that can be used to predict the outcome of experiments. Spacetime is part of the mathematics of relativity and maps to the experimental concept that events take place at a time and a spatial location.

If you want to study Relativity, you could start with Morin's book, the first chapter of which is available free online:

https://scholar.harvard.edu/files/david-morin/files/cmchap11.pdf

This includes an introduction to the concept of spacetime.

 

[Dale]

what exactly is spacetime if it is an actual "real world thing"

Spacetime is the geometry of the “real world”.

a curved medium or "fabric"

Why should geometry be a fabric or medium?

what is the physics of how this guidance works

The physics of how spacetime works is described by the Einstein field equations.

 

[Nugatory]

Given that physics is the study of the physical world, what exactly is spacetime if it is an actual "real world thing", a curved medium or "fabric" guiding the movements of masses, and what is the physics of how this guidance works. As far as I know, space is a vacuum (where not occupied of course) and time is a human concept designating the duration of any specified movement, like Earth's periods of rotationand orbit. Thanks.

We won’t have a productive discussion unless we can say what a “real world thing” is, and the fact that we are compelled to use scare-quotes around the term is a strong hint that we aren’t there.

When we’re studying the physical world we have to start with things that we can (at least in principle) measure. Thus we start with Einstein: time is what a clock measures and distance is what a ruler measures. Observation finds relationships between these that are most effectively described using the methods of differential geometry applied to a pseudo-Riemannian manifold; we have to call that manifold something and “spacetime” is the name that has stuck. Does that make it a “real physical thing”? Who knows? How could we tell? Would the answer affect any measurement or experimental result?

Please take a moment to review this forum’s mission statement. We will gladly work with you if are here to advance your understanding of general relativity and/or to help others do so, but an uncrisp discussion of vaguely defined terms is not what we’re here for.

This thread is closed.