Calculating Synodic Period using Sidereal Period: Is there a Reliable Formula?

  • Context: Undergrad 
  • Thread starter Thread starter University
  • Start date Start date
Click For Summary

Discussion Overview

The discussion revolves around calculating the synodic period of the Moon using its sidereal period, specifically addressing the formula and values involved in the calculation. Participants explore the implications of using different sidereal period values and the resulting synodic period calculations.

Discussion Character

  • Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • Some participants inquire about a formula to calculate the synodic period from the Moon's sidereal period, suggesting the equation involving the Earth's sidereal year.
  • One participant proposes that the synodic period could be 33.3 days, but this is challenged by others who assert that this value is incorrect based on the sidereal period used.
  • Another participant clarifies that the correct sidereal period of the Moon is approximately 27.32 days, contrasting with the 29 days mentioned in the problem statement.
  • Participants discuss the calculation method, with one using the equation and arriving at 36.7 days, which is also questioned by others.
  • Another participant mentions obtaining a value of 0.032 days, which they find unreasonable, leading to confusion about the calculations involved.

Areas of Agreement / Disagreement

There is no consensus on the correct synodic period value, as participants present conflicting calculations and interpretations of the formula. Multiple competing views remain regarding the appropriate values and methods to use in the calculations.

Contextual Notes

Participants express uncertainty regarding the values used in the calculations, particularly the sidereal period of the Moon and the implications of using different values. There are unresolved mathematical steps and assumptions that affect the outcomes presented.

University
Messages
31
Reaction score
0
Is there any formula to calculate Synodic period using for example the Moon's Sidereal period

Lets say moon sidereal period is 29 days what would be its synodic period?
 
Astronomy news on Phys.org
University said:
Is there any formula to calculate Synodic period using for example the Moon's Sidereal period

Lets say moon sidereal period is 29 days what would be its synodic period?

You need to use the period of the Earth's sidereal year and the equation:

[tex]\frac{1}{synodic_{moon}} = \frac{1}{sidereal_{moon}}- \frac{1}{sidereal_{Earth}}[/tex]
 
Does 33.3 days sound right?
 
University said:
Does 33.3 days sound right?

No.

First, it is not the answer you would get if you use 29 days for the Moon's sidereal period, and secondly 29 days is not the Moon's sidereal period (neither is the value you apparently used, if you did the equation right).
 
Thanks for all the hints and help but the exact problem in the text states:

If the sidereal period of the moon is 29.0 days(instead of the correct 27.32 days) what would be its synodic period?

HINT: consider how far around the sun the Earth & Moon would have traveled in 29.0 days
 
University said:
Thanks for all the hints and help but the exact problem in the text states:

If the sidereal period of the moon is 29.0 days(instead of the correct 27.32 days) what would be its synodic period?

HINT: consider how far around the sun the Earth & Moon would have traveled in 29.0 days

Like I said in my last post, 33.3 days is still not correct if you use a value of 29 days for the sidereal period. How did you arrive at that value?
 
I use the equation u posted

1/Synodic period = 1/Moon sidereal Period - 1/earth's sidereal period
= 1/29 -1/365
 
33.3 days is not the answer I get when using those numbers in the equation.
 
E = Earth sidereal year
P = Other planet sidereal year
Then sp = 1/(1/E-1/P)

using this eq I get 36.7 days. Is this correct?
 
Last edited:
  • #10
University said:
E = Earth sidereal year
P = Other planet sidereal year
Then sp = 1/(1/E-1/P)

using this eq I get 36.7 days. Is this correct?

No. I don't understand how you are coming up with these answers with the numbers you are using and the equation given.
 
  • #11
I got 0.032 days but this does not seem to be a reasonable value. Besides the equation is 1/synodic period, so I was assuming 1/0.032 =31.25 days
 

Similar threads

High School Lunar Orbit Issues & Lunar Clocks
  • · Replies 4 ·
Replies
4
Views
1K
Undergrad Synodic Period: Definition & Equation
  • · Replies 1 ·
Replies
1
Views
3K
Undergrad Sidereal Periods: Definition, Equations & Examples
  • · Replies 1 ·
Replies
1
Views
4K
Undergrad Understanding Astronomical Days & Measuring a Year's Length
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad About the relation between number of sidereal and solar days
  • · Replies 27 ·
Replies
27
Views
4K
Graduate Comparing Sidereal & Synodic Reference Frames
  • · Replies 1 ·
Replies
1
Views
3K
Undergrad What causes the variation in Mercury's synodic period?
  • · Replies 2 ·
Replies
2
Views
4K
Undergrad Need Help Creating Moons for Fiction Story
  • · Replies 5 ·
Replies
5
Views
3K
Undergrad What is the synodic period of Mercury?
  • · Replies 5 ·
Replies
5
Views
14K
Undergrad Stable solutions to simplified 2- and 3-body problems?
  • · Replies 6 ·
Replies
6
Views
3K