Why Aren't Laser Beams Bent More When Measuring the Moon's Distance?

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Discussion Overview

The discussion revolves around the bending of laser beams when measuring the distance to the Moon, particularly in the context of gravitational effects as described by general relativity and Newtonian mechanics. Participants explore the implications of mass and gravitational fields on the trajectory of light.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants reference an article discussing the consequences of mass and its relation to gravitational curvature, noting that it is well-written but may lack rigorous mathematical descriptions.
  • One participant challenges a claim from the article that suggests if Earth had no mass, it would not feel the curvature of spacetime, arguing that gravitational acceleration does not depend on mass, as shown by Galileo.
  • Another participant supports the challenge, stating that even massless objects have curved trajectories in a gravitational field, and that light's trajectory is similarly affected in general relativity.
  • There is a question raised about why laser beams sent to the Moon are not bent more significantly, with a response indicating that they are indeed bent, but only by a very tiny amount.

Areas of Agreement / Disagreement

Participants express disagreement regarding the interpretation of gravitational effects on mass and light. While some agree on the principles of gravitational curvature, the extent to which laser beams are bent remains a point of inquiry.

Contextual Notes

The discussion includes assumptions about gravitational effects and the nature of light in gravitational fields, which may not be fully resolved or universally accepted among participants.

fresh_42
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Not that this article here can compete with mathematical descriptions or "real" physics but it is well written and fast to read and may provide some answers to the repeating questions about the different consequences of mass.
 
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fresh_42 said:
Not that this article here can compete with mathematical descriptions or "real" physics but it is well written and fast to read and may provide some answers to the repeating questions about the different consequences of mass.
I have read only till it says:
"If Earth had no mass, it wouldn’t feel the curvature of the well and would fly away in a straight line. That’s general relativity in a funnel shaped nut-shell."
This is incorrect: Galilei showed that gravitational acceleration doesn't depend on mass, so even a massless object's trajectory is curved in a gravitational field. The general relativity result is similar, in fact light trajectory is curved in this theory too, just twice as what results from Newtonian mechanics.

--
lightarrow
 
lightarrow said:
I have read only till it says:
"If Earth had no mass, it wouldn’t feel the curvature of the well and would fly away in a straight line. That’s general relativity in a funnel shaped nut-shell."
This is incorrect: Galilei showed that gravitational acceleration doesn't depend on mass, so even a massless object's trajectory is curved in a gravitational field. The general relativity result is similar, in fact light trajectory is curved in this theory too, just twice as what results from Newtonian mechanics.

--
lightarrow
Sounds correct. But then why aren't the laser beams bent we send to the moon to measure it's distance?
 
fresh_42 said:
Sounds correct. But then why aren't the laser beams bent we send to the moon to measure it's distance?
They are bent, but by a very tiny amount.
 

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