Gravitational Waves & Neutron Stars/Black Holes: Observed Velocity Decrease

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Discussion Overview

The discussion centers on the observation of gravitational waves and their effects on the velocity of closely orbiting massive objects, specifically neutron stars and black holes. Participants explore whether there have been direct measurements of decreasing velocity or if the observed phenomena are attributed to the spiraling motion due to gravitational wave emission.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes that two closely orbiting massive objects are expected to release gravitational waves, leading to a loss of velocity energy as they spiral into each other.
  • Another participant references the Hulse-Taylor binary pulsar, highlighting that a decrease in the orbital period was observed, which may relate to the question of velocity changes.
  • A different viewpoint suggests that if two orbiting objects lose energy, their velocity should theoretically increase, and questions whether this has been measured through the Doppler effect.
  • A later reply confirms that measuring the orbital period is necessary, implying that velocity measurements are indeed part of the observational process.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between energy loss and velocity changes, with some focusing on observed orbital period changes and others questioning the implications of those observations. The discussion remains unresolved regarding the direct measurement of velocity reduction versus the attribution of spiraling motion to gravitational wave emission.

Contextual Notes

There are limitations regarding the assumptions made about energy loss and velocity changes, as well as the dependence on definitions of velocity in the context of gravitational wave emission. The discussion does not resolve these aspects.

Rorkster2
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2 closely orbiting massive objects are predicted to deserve the fabric of spacetime so much that they will release a ripple of gravitational waves. When geavitational waves are released, they slowly loose velocity energy and spiral into one another. 2 pulsars were discovered orbiting each other which prompted a Nobel Prize being awarded in 1993.

My question is have we measured decreasing velocity between 2 massive objects in a tight orbit or have we observed them spiraling into one another, which is then attributed to velocity reduction through releasing gravitational waves?
 
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What was observed in the Hulse-Taylor binary pulsar was a decrease in the orbital period. See the "Binary Pulsar" entry in Wikipedia.
 
If two orbiting objects lose energy, their velocity increases. At least in theory, it should be possible to observe their velocity via the doppler effect. Maybe this was done, check the publications.

Edit: Oh wait, of course they measured the velocity - it is necessary to measure the orbital period.
 
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http://www.lightandmatter.com/html_books/genrel/ch09/ch09.html#Section9.2
 
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