What is the synodic period of Mercury?

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    Mercury Period
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Discussion Overview

The discussion centers around the synodic period of Mercury, specifically its average value and the calculations involved in determining it. Participants explore various sources and methods for calculating this astronomical period.

Discussion Character

  • Technical explanation, Mathematical reasoning, Debate/contested

Main Points Raised

  • One participant inquires about the synodic period of Mercury, noting that some sources cite a value around 115.877484 days.
  • Another participant provides a link to a NASA fact sheet that states the synodic period as 115.88 days, which raises concerns about rounding.
  • A participant suggests a method for calculating the synodic period using the orbital periods of Mercury and Earth, presenting a formula involving the sidereal years of both planets.
  • One participant calculates the synodic period as 115.8772 days using specific values for the orbital periods of Mercury and Earth, while noting that some sources prefer a value of 115.8776 days.
  • Another participant refines the calculation with updated values, arriving at 115.877623 days and mentions that other references support this value.

Areas of Agreement / Disagreement

Participants express differing views on the exact value of the synodic period of Mercury, with no consensus reached on a single definitive number. There are multiple calculations presented, and some sources are preferred over others.

Contextual Notes

Participants note potential discrepancies in the values due to rounding and the choice of orbital period data, which may affect the calculations. The discussion does not resolve these uncertainties.

Helios
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What is the synodic period of Mercury? What is the average synodic period of Mercury? I have combed the internet. Some sources use a number around

115.877484 days and they seem sure of themselves.

I don't own astronomy references. Help please
 
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That page just gives

115.88 days

and I have a feeling that this is a rounded-off number.
 
You can calculate the synoptic period from the orbital period of mercury and Earth
E = Earth sidereal year
P = Other planet sidereal year
Then sp = 1/(1/E-1/P)
 
I would calculate this as ( correcting mgb's equation )
P = 87.9691
E = 365.256363
sp = 1/(1/P-1/E) = 115.8772

However, a lot of internet sources, even encyclopedic ones, have a preference for

sp = 115.8776 days
 
and with possibly better values, I would now calculate this as
P = 87.96934
E = 365.256363
sp = 1/(1/P-1/E) = 115.877623

and some other references have concurred with this datum
 

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