B Mass of Space (B but approaching I)

B
Thread starter Thkaal
Start date Feb 14, 2023
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Mass mass and energy Space Space and time

AI Thread Summary

Space is expanding, but this expansion does not involve objects being moved by an external force; rather, they are moving apart due to the geometry of spacetime itself. The concept of vacuum energy density is discussed, with a reference to its estimated value, but the conversation emphasizes that energy conservation is not straightforward in an expanding universe. The idea that space itself expands is clarified, indicating that it is more accurate to say the distance between unbound objects increases without new space being created. Misunderstandings about the Planck length and the nature of spacetime geometry are addressed, asserting that current models do not support the existence of smallest units of space or time. Overall, the discussion highlights the complexities of cosmological expansion and the nature of energy in the universe.

Feb 25, 2023

PeterDonis

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timmdeeg said:

Quite often here in PF it comes to a point where someone explains expansion of the universe doesn't mean that space expands, it means increasing distances. This seems quite vague and with no reference to coordinate dependence. But it at least points to right direction. Would you agree to that?

Sort of. When you fill in the missing information about what "increasing distances" means, the coordinate dependence appears. So whether it "points in the right direction" depends on what your goal is.