Detecting Space Time: Gravitational Radiation

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Discussion Overview

The discussion centers around the detection of space-time, particularly exploring the concept of gravitational radiation as a potential method. Participants consider various approaches and interpretations related to the detection and measurement of space-time, including theoretical and experimental perspectives.

Discussion Character

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

Main Points Raised

  • One participant suggests that gravitational radiation is a way to detect space-time, questioning if it is the only method available.
  • Another participant argues that space-time is not a tangible entity and implies that experiments verifying special and general relativity serve as indirect evidence of space-time.
  • A different viewpoint states that any event occurring in space must belong to space-time, implying a fundamental connection between events and the fabric of space-time.
  • Radar detection is proposed as a method to consider the space-time coordinates of distant events, alongside photographic detection.
  • A historical reference is made to Gauss, who examined the properties of space through geodesy, noting that he found no significant deviation from Euclidean geometry in his measurements.
  • One participant questions the clarity of the term "detect space-time," suggesting that detecting the curvature of space-time may be a more accurate interpretation, referencing Gauss's work and the challenges of measurement in relativity.
  • Another participant elaborates on the difficulties of measuring angles in large triangles formed by celestial bodies, discussing the implications of using rigid materials versus laser beams for measurement, and how gravitational effects could influence the perceived geometry.

Areas of Agreement / Disagreement

Participants express differing views on what it means to "detect" space-time, with some focusing on gravitational radiation and others on the curvature of space-time. The discussion remains unresolved, with multiple competing interpretations and methods proposed.

Contextual Notes

Participants highlight limitations related to measurement techniques, the definitions of space-time, and the assumptions underlying their proposed methods. The discussion reflects the complexities involved in detecting and interpreting space-time phenomena.

wolram
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It is just a thought, but how can space time be detected? i guess gravitational radiation is one way, is this the only way?
 
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Detected? It's not really like a tangible thing. I guess if you wanted to have experiment supporting the notion of space-time, you'd just have to look to those verifying special and general relativity or relativistic quantum mechanics etc.
 
Almost by definition, if something happen somewhere, then that 'somewhere' belongs to spacetime.
 
radar detection

wolram said:
It is just a thought, but how can space time be detected? i guess gravitational radiation is one way, is this the only way?
If you think about the space time coordinates of a distant event you could use the radar or photographic detection.
 
AFAIK Gauss was the first to examine the properties of space. When working as a geodesist he checked the sum of angles of large triangles (~100 km). Of course he found no significant deviation from 180°.
 
It's not at all clear what you mean by "detect space-time". Ich assumed you meant "detect the curvature of space-time" which is probably the best interpretation. As he said, Gauss attempted to determine if space is Euclidean by measuring the angles in a triangle formed by 3 mountain peaks using the best surveying equipment. He found any deviation from 180 degrees to be less than the error of measurement.

One difficulty with that is defining how you are going to measure things. Imagine using, say, Pluto, Uranus, and Neptune, at times when they are farthest apart in their orbits, as vertices of a triangle and thin steel bars as straight edges! Since, in relativity, there are no perfectly rigid materials, those bars would "sag" inward toward the sun- you would find the angles to be less than 180 degrees- elliptic geometry- and dependent upon the rigidity of the materials.

It would make much more sense to use laser beams as straight lines. Since it has been experimentally verified that light beams bend as they pass a star (the sun), your lines would appear curved and you would find the sum of the angles to be greater than 180 degrees- hyperbolic geometry- and that the curvature changed from moment to moment as the masses in the system moved.
 

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