Space-time Without Matter? I Don’t Think So!
Theoretical physicists often speak of space-time as if it were some entity that was independent of matter. Einstein, on the other hand, emphatically stated that without matter there can be no space-time. Here are two reasons to agree with Einstein.
- Without any objects there are no spatial distances. Ask yourself: what is the spatial distance between nothing and nothing? Answer: the concept of spatial distance makes no sense when there are not objects present. Moreover if there are no objects to oscillate, move around, or rotate, then there is no time. Ask yourself: how could the concept of time have any meaning without objects? Answer: it cannot.
2. There is also another way to approach this inseparable link between matter and space-time. Take a location in the real physical cosmos that we conventionally model in terms of virtually empty space-time. Say, midway between the orbits of Saturn and Neptune for a given period of time. True there are some solar wind particles and ions moving through the region, and the occasional cosmic ray blasting through, but it is also a region of very high vacuum that approximates “empty” space-time. Yet further consideration reminds us that this region is within the Solar System, i.e., it is part of the interior of an object. This region is also part of the interior of a much larger object that we know as the Milky Way Galaxy. Further, the MWG is within the Local Groups of galaxies, which is within the Local Supercluster of galactic groups, which is part of the vast Cosmic Web. And who knows for sure whether the cosmological hierarchy ends conveniently at the limit of our current observational capabilities?
It bears consideration that any region of real physical reality is actually inside a hierarchical succession of objects. Nowhere can you find space-time that is independent of objects, i.e., matter.
When we are talking about space-time, we are really talking about the internal geometry of objects — not something independent of matter.
Einstein was right, as usual.
RLO