How Fast Is the Moon Moving Away from Earth?

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Discussion Overview

The discussion centers on the rate at which the Moon is moving away from Earth, specifically the average rate of 3.82 ± 0.07 cm/year. Participants seek to clarify the exact distance between the Earth and the Moon at the time this measurement was made, as well as the methodology behind deriving this average rate.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant states the average rate at which the Moon is moving away from Earth is 3.82 ± 0.07 cm/year and seeks the exact distance at the time this data was measured.
  • Another participant suggests that there cannot be a single exact value for the distance since it is an average derived from decades of lunar ranging experiments.
  • A third participant provides a link to a resource that allows users to calculate the distance from Earth to the Moon at any given time, indicating that specific distances can be generated based on user-defined parameters.
  • One participant reiterates the point that the average value does not correspond to a single distance, emphasizing the reliance on historical data from lunar ranging experiments.

Areas of Agreement / Disagreement

Participants generally agree that the average distance is derived from multiple measurements over time, but there is no consensus on the existence of a single exact distance corresponding to the average rate of separation.

Contextual Notes

The discussion highlights the complexity of measuring distances in astronomy and the implications of averaging over time, but does not resolve the specifics of the measurements or the definitions involved.

Who May Find This Useful

Individuals interested in lunar science, astronomy, and the methodologies of distance measurement in space may find this discussion relevant.

elistein
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Hi all

It's a well known fact that the moon is drawing away from Earth by 3.82 ± 0.07 cm/year.

I was googling a lot to find the exact distance between Earth - moon

that this data was measured.

A plain number or a link will be much appreciated.

Thanks in advance

Elistein
 
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Hi Dr. Courtney

Thanks for your reply.

Yes, I know about the min, max and average distance.

What I'm interested: what was the exact distance at the time this data was determined:

"The Moon is spiraling away from the Earth at an average rate of 3.8 cm (1.5 in) per year"
 
There can't be an exact/single value for something that is an average. The value was almost certainly derived from decades of lunar ranging experiments.
 
If you want the distance from Earth to Moon at any given time, go here:

http://ssd.jpl.nasa.gov/horizons.cgi#top

And set the Moon as the target body.

The time span setting will allow you to set the date, time, time duration and time steps for the generated list. Under table settings, you can choose which properties you want to see in the list.
 
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russ_watters and Janus

Thanks for your replies. I'll look into it right away
 
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