Are the forces of gravity subject to the Doppler effect?

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Discussion Overview

The discussion explores the potential relationship between the forces of gravity and the Doppler effect, particularly in the context of gravitational fields and their variations due to motion. Participants examine whether gravitational forces could be influenced by redshift and Doppler effects, and how this might relate to phenomena such as the precession of planetary orbits and the flyby anomaly.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant suggests that gravitational force could vary according to the redshift equation, proposing that objects moving away from a gravitational system might experience a decrease in gravitational force from behind, while those moving towards it might experience an increase from the front.
  • Another participant questions the validity of applying the Doppler correction formula to gravitational forces, implying that such an application may not be appropriate.
  • Some participants clarify that the Doppler effect traditionally applies to frequency and wavelength, raising questions about its relevance to forces.
  • A participant discusses the relationship between photons and electromagnetic forces, noting that the Doppler effect applies to electromagnetic interactions, which are mediated by photons.
  • One participant speculates that while the Doppler effect may not apply to gravitational forces, it could be relevant to gravitational waves.
  • Another participant acknowledges the classical and relativistic components of the Doppler effect, suggesting that it could apply to gravitational waves under certain conditions.
  • There is a contention regarding the physical plausibility of extending the Doppler shift concept to static fields, with some arguing it may be mathematically reasonable but not physically applicable.

Areas of Agreement / Disagreement

Participants express differing views on whether the Doppler effect can be applied to gravitational forces, with some asserting it cannot while others suggest it may have relevance in specific contexts, such as gravitational waves. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants highlight limitations in applying the Doppler effect to gravitational forces, including the need for a plausible mechanism for static fields to exhibit wave-like properties. There are also unresolved questions regarding the assumptions behind the proposed relationships.

kmarinas86
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Was it considered that the force of gravity could vary according to the redshift equation?

1+z=\frac{1+v \cos (\theta)/c}{\sqrt{1-v^2/c^2}}

If those who consider this are right, then it would imply that an object leaving a gravitational system would experience a slight decrease in the gravitational force from behind, and an object entering a gravitational system would experience a slightly increased gravitational force in front of it. Therefore, an object flying-by the Earth would experience a gravitational field that is slightly ahead it even if it is at the apex of its trajectory.[Note 1]

Also, if the object were to travel between latitudinal lines, in the same direction as the planet's spin, then a transverse Doppler effect would reduce the force of gravity from latitudes further from the equator more so than they would for latitudes closer to the equator, resulting in a slight gravitational pull towards the equator, giving it a lower effective potential.[Note 2]

If such were to occur, is this something that can be accommodated by General Relativity?[Note 3]

1) Could that not explain the anomalous precession of the perihelion of Mercury, Venus, etc.?
2) Could that not explain the flyby anomaly?
3) ...I'm not expecting that it will.
 
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kmarinas86 said:
If those who consider this are right, [...]
Does "those who consider this" mean you?

No, you can't just randomly apply the Doppler correction formula to randomly chosen physical variables.
 
bcrowell said:
Does "those who consider this" mean you?

No, you can't just randomly apply the Doppler correction formula to randomly chosen physical variables.

So the forces of gravity are not subject to the Doppler effect? Or are you just saying that you cannot randomly apply the Doppler effect to the forces of gravity, i.e. haphazardly?
 
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The Doppler effect applies to frequency and wavelength. How does it apply to forces? :confused:
 
jtbell said:
The Doppler effect applies to frequency and wavelength. How does it apply to forces? :confused:

Frequency and wavelength apply to the photon. The photon is a gauge boson. It is a particle which allows for the transfer of energy from one body to another through a fundamental force, and in this case that fundamental force is electromagnetism. The magnitude of amount of momentum which a mass-bearing object receives from a photon is given by the relation p=\frac{h}{\lambda}, where p is the momentum of the photon, h is Planck's constant, and \lambda is the wavelength of the photon in the frame of reference of that mass-bearing object.

So we know of at least one type of force (electromagnetic), which is mediated through a type of field (an electromagnetic field), clearly obeying the relativistic Doppler formula.
 
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I am not sure but it can apply to gravitational waves but not gravitational forces.
 
The Doppler shift has two parts, the classical part which is your velocity makings wave crests appear to run by you faster or slower. There's also a relativistic component involving the time dilation.

Assuming you were heading toward a source of (low amplitude) gravitational waves, the same Doppler shift would apply as does for light waves.

The general phenomenon is not limited to waves only, it's just that it was discovered that way. But it's perfectly reasonable mathematically to extend the Doppler shift concept to non-wave fields.
 
Antiphon said:
[..]
The general phenomenon is not limited to waves only, it's just that it was discovered that way. But it's perfectly reasonable mathematically to extend the Doppler shift concept to non-wave fields.

Mathematically reasonable perhaps, but physically not - except if you can make it plausible that static fields have something like propagating wave crests that can be counted.
 

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