Gravitational waves - second question

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Discussion Overview

The discussion revolves around the detection of gravitational waves in the context of an expanding universe and the relative motion of celestial bodies, specifically considering whether gravitational waves can be detected when Earth accelerates around the Sun.

Discussion Character

  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant questions the detection of gravitational waves if the universe is expanding and suggests that if the fabric of spacetime is expanding at the same rate as local celestial bodies, it may affect detection.
  • Another participant argues that the galaxy is not expanding significantly and that gravitational waves from local sources should always be detectable unless extreme conditions arise, such as the cosmological constant causing objects to recede faster than light.
  • A third participant expresses a personal preference for the concept of an ether but acknowledges that many consider the "fabric of space" to be merely a metric, suggesting that gravitational influence exists from matter in the observable universe, albeit often too small to detect.
  • A later reply thanks the second participant for clarifying the initial question and indicates that the explanation was helpful.

Areas of Agreement / Disagreement

Participants do not reach a consensus; there are competing views regarding the implications of an expanding universe on the detection of gravitational waves, and the discussion remains unresolved.

Contextual Notes

Some statements contain internal inconsistencies, and there are unresolved assumptions about the nature of spacetime and gravitational influence at various distances.

tonyb1969
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Gravitational "waves" - second question

Assuming our concept of the universe expanding (perhaps) and that the fabric of space time is expanding at the same rate as our galaxy and solar system (velocity equal, so relatively motionless), would we still be able to detect gravitational waves when a planet (Earth, for example) accelerates around the Sun?
 
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Your question includes internal inconsistencies and I have no idea what "velocity equal so relatively motionless" means.

Our galaxy is NOT expanding to any appreciable nor measureable degree. Only at (great) cosmological distances is dark energy (the cosmological constant) large enough to over come gravity and enable spacetime to expand. At ginormous distances from us, galaxies are receding at greater than the speed of light and hence gravitational waves from those galaxies will never reach us., nor will anything else; locally gravitational waves should always reach us unless the cosmological contant grows in the future to such a degree that, say, the sun and Earth move away from each other at greater than light speed.

If that doesn't not make enough sense try wikipedia at

http://en.wikipedia.org/wiki/Observable_universe

and note other wiki sources to the right under the box PHYSICAL COSMOLOGY. Beware "horizons" in cosmology are not immediately obvious.
 


While I personally like the idea of an ether, most say the "fabric of space" is just a metric. I would think the influence of gravity is present from any matter in the observable universe but in most cases would be too small to detect. Naty1 did well pointing out if you can't see the light, you will not feel the gravity.
 


Sincere thanks for overcoming the naive challenge of my question (I was having a hard time knowing how to word it). Your explanation, though, did answer what I was trying to get at. I'll also look on wikipedia as suggested...thanks...
 

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