Curved space and gravitational waves

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Discussion Overview

The discussion revolves around the nature of gravitational waves and the relationship between gravity, spacetime, and the concept of temporal velocity. Participants explore whether gravitational waves are purely temporal and how objects at rest interact with the curvature of spacetime.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question if gravitational waves are purely temporal and propose that an object with no spatial velocity experiences gravity due to temporal velocity.
  • Others argue that there is no such thing as temporal velocity, emphasizing that the four-velocity is timelike.
  • It is suggested that gravity is a result of the curvature of spacetime, not just space, and that even point particles have temporal extent.
  • One participant notes that the curvature in spacetime planes is what is important for gravity, while curvature of space is less significant except in extreme cases.
  • There is a distinction made between gravitational waves and everyday experiences of gravity, with a claim that they are related but not the same phenomenon.
  • A later reply introduces the concept of a worldtube to represent each object in spacetime.

Areas of Agreement / Disagreement

Participants express disagreement on the concept of temporal velocity and its relevance to gravitational waves, with no consensus reached on the nature of gravitational waves or the implications of spacetime curvature.

Contextual Notes

Some limitations include the unclear definitions of temporal velocity and the dependence on interpretations of spacetime curvature. The discussion does not resolve the mathematical implications of these concepts.

Nidhi1007
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TL;DR
An object moving in a straight line appears to be attracted to a massive body due to the curvature of space, this gives the appearance of gravity attracting the body. But why does a body at rest tend to move along the curvature of space?
Are gravitational waves purely temporal? An object with no spatial velocity experiences gravity due to temporal velocity?
 
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Nidhi1007 said:
temporal velocity

There is no such thing as temporal velocity.
 
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Nidhi1007 said:
Summary:: An object moving in a straight line appears to be attracted to a massive body due to the curvature of space, this gives the appearance of gravity attracting the body. But why does a body at rest tend to move along the curvature of space?
It is curvature of spacetime, not curvature of space. Even a point particle has temporal extent.
 
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weirdoguy said:
There is no such thing as temporal velocity.
No, but the four-velocity is timelike.
 
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Dale said:
It is curvature of spacetime, not curvature of space. Even a point particle has temporal extent.
Thank you
 
Nidhi1007 said:
But why does a body at rest tend to move along the curvature of space?
Because it isn't the curvature of space, it's the curvature of spacetime. The curvature of space really isn't important for gravity except for the most precise measurements or in really extreme circumstances. It's actually the curvature in space-time planes that is important for gravity, and objects have an extent in time.
Nidhi1007 said:
An object with no spatial velocity experiences gravity due to temporal velocity?
Better to say that it is because all objects have an extent in time. There is a kind of meaning to "velocity in a timelike direction" and you do see this written in popsci, but it's a kind of misdirection to associate four velocity with the more familiar velocity from school physics. They are rather different things.
Nidhi1007 said:
Are gravitational waves purely temporal?
Gravitational waves have nothing to do with this. Gravity as we experience it every day and gravitational waves are related phenomena, but they are not the same thing.
 
Ibix said:
It's actually the curvature in space-time planes that is important for gravity, and objects have an extent in time.
We can say each object is represented in spacetime by a worldtube.
 

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