210 reputation
17
bio website
location Augsburg, Germany
age 39
visits member for 1 year, 6 months
seen Sep 8 at 10:41

Oct
2
awarded  Yearling
Dec
11
comment How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
One reason for my question is that one can state Einstein's field equation as follows: The scalar curvature of space (using my definition) is (up to a factor of $4 \pi$ in natural units) the mass density as measured by the observer. So in principle, mass should be measurable by statically measuring lengths, in contrast of kinematic experiments involving the flow of time.
Dec
11
comment How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
Normal neighbourhoods in the actual space-time seem to be quite large, so I am hoping that measurements are possible on a macroscopic enough scale.
Dec
11
comment How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
Added an extra paragraph. Please let me know in case you still think it is not well-defined.
Dec
11
revised How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
Made the question more precise after one answer hinted at a few problems.
Dec
11
comment How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
You are right, my question isn't formulated in a very precise manner when it comes to the definition of space and space-like. In fact, I was thinking locally. I am going to amend my question accordingly.
Dec
3
comment How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
Does this describe space-like distances well? I am thinking of the deflection of light by a star. As it is well known, general relativity gives twice the deflection angle than Newtonian gravity. One half is directly through the acceleration by the mass (which is also in Newton's theory), while the other half is due to the curvature of the space hyper-surface. My question is more or less about this second half. Is this linked in a simple way to the space-like distances you measure with the laser-ranging experiment you are suggesting?
Dec
3
awarded  Nice Question
Dec
3
awarded  Commentator
Dec
3
comment How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
That sounds like a mere mathematical answer, not a physical one.
Dec
3
revised How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
fixed grammar
Dec
2
awarded  Editor
Dec
2
revised How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
added 150 characters in body
Dec
2
awarded  Tumbleweed
Dec
2
asked How does one measure space-like geodesics? Or: What is the physical interpretation of space-like geodesics?
Oct
22
accepted Trajectories of particles with spin in Einstein-Cartan theory
Oct
22
asked Trajectories of particles with spin in Einstein-Cartan theory
Jul
17
awarded  Supporter
Jul
17
comment What is a set of minimal assumptions needed to interpret general relativity?
After having thoroughly throught through it, I agree that the Lagrangian approach is probably the best; I also accepted your answer. P.S.: Do you know a good reference for a Lagrangian matter term for a perfect fluid?
Jul
17
awarded  Scholar