What is the speed of gravitational waves?

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Discussion Overview

The discussion centers around the speed of gravitational waves, particularly in the context of general relativity and hypothetical scenarios involving the movement of massive objects like the Sun. Participants explore the implications of gravitational waves propagating at the speed of light and the conditions under which they are generated.

Discussion Character

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

Main Points Raised

  • One participant questions the speed of gravitational waves and suggests that if the Sun were to move suddenly, it would result in a gradual wave of disorder affecting the orbits of planets over time.
  • Another participant asserts that gravitational waves travel at the speed of light, although they note that this speed has yet to be experimentally measured.
  • Concerns are raised about the formulation of thought experiments involving the sudden movement of the Sun, emphasizing the importance of conservation of energy and momentum in general relativity.
  • It is noted that a star moving in a straight line does not produce gravitational waves, while oscillating sources, such as binary stars, do generate them.
  • A later reply introduces a question about the nature of inflation and how it relates to the expansion of space and the movement of objects appearing to separate faster than light.

Areas of Agreement / Disagreement

Participants generally agree that gravitational waves propagate at the speed of light, but there is no consensus on the implications of hypothetical scenarios involving the sudden movement of massive objects. The discussion remains unresolved regarding the relationship between gravitational waves and cosmic inflation.

Contextual Notes

Participants express uncertainty about the conditions under which gravitational waves are produced and the implications of general relativity for thought experiments involving massive objects. The discussion highlights the complexity of these concepts without reaching definitive conclusions.

s.martie07
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I was wandering through the net when I came to know that the Newtonian gravitation suffers discrepancies at some regions of space.

On further reading I came to know about gravitational waves. Fundamentally matter has mass and mass is responsible for gravity. Then it may be anything from small meteor to big galaxies. They all form their own gravitational waves in space time fabric.
My question is

What is the speed of such gravitational waves?

If it is the speed of light, it means that if the Sun is moved from its original position suddenly, there will be a gradual wave of disorder moving outwards in our solar system.

That means Earth will lose its orbit after 7.5 minutes?
also Pluto will lose its orbit after 328 minutes?

I do not understand this phenomena.
 
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You're right, it is the speed of light, although it is yet to be experimentally measured. You're also right that the planets will lose their orbit in order of distance from the Sun.
Skip to 7:20 in this video for a visual explanation
Hopefully someone else will give more information.
 
Last edited by a moderator:
In general relativity you need to be careful in formulating such thought experiments as "what if the sun suddenly moved", because conservation of energy and momentum are central to the theory and the sun cannot suddenly move or disappear. Also a star simply moving along in a straight line does not produce a wave.

An oscillating source such as a pair of stars orbiting about one another does cause gravitational waves, and they propagate outward at the speed of light.
 
Bill_K said:
In general relativity you need to be careful in formulating such thought experiments as "what if the sun suddenly moved", because conservation of energy and momentum are central to the theory and the sun cannot suddenly move or disappear. Also a star simply moving along in a straight line does not produce a wave.

An oscillating source such as a pair of stars orbiting about one another does cause gravitational waves, and they propagate outward at the speed of light.

As I understand gravitational waves are simply space-time waves. Given that then what exactly is inflation if space can expand in a manner such that two objects would appear to be moving apart from one another faster than light?
 

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