What is space-time made out of ?

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Discussion Overview

The discussion centers around the nature of space-time, particularly what it is "made out of" and how it relates to matter and gravitational fields. Participants explore theoretical implications of General Relativity, the concept of vacuum, and the relationship between mass and space-time.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that "empty" space is not truly empty, suggesting it contains quantum energy fluctuations that manifest as temporary energy-anti-energy pairs.
  • Others argue that space-time is not made out of anything, and its curvature is dependent on the presence of tidal forces, while some assert that a uniform gravitational field results in flat space-time.
  • There is a contention regarding the interchangeability of the terms "space-time" and "gravitational field," with some asserting they are synonymous while others maintain they represent different concepts.
  • Participants discuss the implications of mass on space-time, with some suggesting that mass creates a gravitational field that can be flat or curved, while others question the analogy between gravitational fields and other forces like electromagnetic fields.
  • Some participants express uncertainty about the nature of space-time in the absence of mass, referencing vacuum solutions to Einstein's equations that suggest gravitational fields can exist without matter.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of space-time, with multiple competing views and ongoing debate about its properties and relationship to mass and gravitational fields.

Contextual Notes

There are unresolved questions regarding the definitions of space-time and gravitational fields, as well as the implications of vacuum solutions in general relativity. The discussion reflects varying interpretations of theoretical concepts without definitive conclusions.

  • #31
There aren’t any 4 spatial dimensions. There are only three. There are the x, y, and z Cartesian coordinates, and that is it.
Exactly. And as long as you consider straightness by these 3 dimensions, you can easily make adjustments to move in a "straight line" with curved non-euclidean space.
 
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  • #32
Originally posted by FZ+
Exactly. And as long as you consider straightness by these 3 dimensions, you can easily make adjustments to move in a "straight line" with curved non-euclidean space.

My point is, with these three dimension and the x, y, and z coordinate system, that represents Euclidean space. If we insert spherical masses and their curved gravitational fields into this coordinate system, we still have the same coordinate system, and inserted into it are curved masses and curved gravity fields. It’s like inserting a spherical basketball into a cubical box. The ball remains spherical and the box remains cubical. The box doesn’t change shape to conform to the outline of the ball.
 
  • #33
David - it isn't that space distorts into a sphere around a spherical mass - what occurs is a change in the measured radius of a sphere relative to the surface area of the sphere measured at that radius - in other words, the surface area of a spherespace encompassing a mass is no longer exactly 4(pi)R^2 For the Sun, the change (excess radius) if I remember correctly is about 1/2 a kilometer
 
  • #34
Spacetime is simply how we describe and try to understand nature.
Spacetime is made of what the Euclidean space is made of - just a mathematical description. The space and time are created in the process of perception from multiscale sources of unifying interaction according to the emerging theory of interaction developed by the space
physicist Eugene Savov.
 
  • #35
Originally posted by David
There aren’t any 4 spatial dimensions. There are only three. There are the x, y, and z Cartesian coordinates, and that is it.

I think he's extending the analogy to help understanding. He's not saying there are 4 spatial dimentions in Relativity.
 
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