# Help with formula to calculate the precession rate change

• I
• phi
In summary, the speaker discusses their attempt to calculate the precession rate variation using a formula from a website. They also mention alternative formulas and estimated precession rates for different years. They then ask for help with their calculations, suspecting a typo in the original formula.
phi
First time caller, I'm a newb so go easy on me.

So I was trying to work through a calculation to figure out the precession rate variation in terms of the Precession of the Equinox.

I came across the following formula from (https://endgametime.wordpress.com/understanding-precession-of-the-equinox/)

I quote:

If we are moving away from apoapsis as proposed, our orbital velocity should be increasing – we are speeding up with respect to the binary center of mass – which means that the period of revolution perceived over astronomically short periods of time is decreasing; this in turn requires the constant of precession to increase as time goes by. Currently the yearly change is about 0.000349”/y, but that will continue to increase for a few more years, until the Sun reaches periapsis. In terms of the calculated period of revolution, that corresponds to a yearly decrease of .178 years, ignoring the short cyclic influences of nutation, etc. This roughly corresponds with the changes in precession calculations that have been reported in the literature.

Therefore, we make the following estimates for the years 2011:

Year Precession

Period of Revolution (years)

2010 50.24”/y

25,792.035

2100 50.325866”/y

25792.164

In 1900, Simon Newcomb offered a formula for precession: 50.2564” + 0.000222 * (year – 1900) (U.S. Naval Observatory 1900)

We offer the following alternative formula based on the proposed binary system model: 50.245223” – 0.000349 * (2012- year)

Observed precession has changed by 0.0337 from 1900 to 2000, for a yearly change of 0.000337” . This precession delta is approximately ten times closer to our proposed annual precession of 0.000349” than Newcomb’s annual precession adjustment of 0.000222”.

Minimum precession is about 1 degree every 84 years when the Sun is at apoapsis, and the maximum precession is about one degree every 71.665 years when the Sun is near periapsis. The Earth will average about one degree of precession per 77.83 years over the 24,000 year cycle.

I tried using their formula to calculate the precession rate at year 2100
as above (50.245223” – 0.000349 * (2012- year))

So I used:

50.245223 - .000349 * (2012 - 2100)

50.245223 - .000349 * -88

50.245223 - -0.030712

I get = 50.275935

Their answer above though is: 50.325866”/y

I cannot for the life of me figure out what I am doing wrong. Any help would be greatly appreciated, starting to lose my mind :-)

Thanks!
Φ

phi said:
First time caller, I'm a newb so go easy on me.

So I was trying to work through a calculation to figure out the precession rate variation in terms of the Precession of the Equinox.

I came across the following formula from (https://endgametime.wordpress.com/understanding-precession-of-the-equinox/)

I quote:

If we are moving away from apoapsis as proposed, our orbital velocity should be increasing – we are speeding up with respect to the binary center of mass – which means that the period of revolution perceived over astronomically short periods of time is decreasing; this in turn requires the constant of precession to increase as time goes by. Currently the yearly change is about 0.000349”/y, but that will continue to increase for a few more years, until the Sun reaches periapsis. In terms of the calculated period of revolution, that corresponds to a yearly decrease of .178 years, ignoring the short cyclic influences of nutation, etc. This roughly corresponds with the changes in precession calculations that have been reported in the literature.

Therefore, we make the following estimates for the years 2011:

Year Precession

Period of Revolution (years)

2010 50.24”/y

25,792.035

2100 50.325866”/y

25792.164

In 1900, Simon Newcomb offered a formula for precession: 50.2564” + 0.000222 * (year – 1900) (U.S. Naval Observatory 1900)

We offer the following alternative formula based on the proposed binary system model: 50.245223” – 0.000349 * (2012- year)

Observed precession has changed by 0.0337 from 1900 to 2000, for a yearly change of 0.000337” . This precession delta is approximately ten times closer to our proposed annual precession of 0.000349” than Newcomb’s annual precession adjustment of 0.000222”.

Minimum precession is about 1 degree every 84 years when the Sun is at apoapsis, and the maximum precession is about one degree every 71.665 years when the Sun is near periapsis. The Earth will average about one degree of precession per 77.83 years over the 24,000 year cycle.

I tried using their formula to calculate the precession rate at year 2100
as above (50.245223” – 0.000349 * (2012- year))

So I used:

50.245223 - .000349 * (2012 - 2100)

50.245223 - .000349 * -88

50.245223 - -0.030712

I get = 50.275935

Their answer above though is: 50.325866”/y

I cannot for the life of me figure out what I am doing wrong. Any help would be greatly appreciated, starting to lose my mind :-)

Thanks!
Φ
If you use their formula to calculate the value for 1900 it comes out too low. I suspect a typo: their formula should be 50.29522...

Awesome that would explain it! Thanks so much for the reply!

## What is the precession rate change formula?

The precession rate change formula is used to calculate the change in the rate at which an object's axis of rotation changes over time. It is typically represented as Δω/Δt, where Δω is the change in angular velocity and Δt is the change in time.

## How is the precession rate change formula derived?

The precession rate change formula is derived from the principles of angular momentum and torque. It takes into account the external forces acting on the rotating object, such as gravity and friction, and the object's moment of inertia.

## Can the precession rate change formula be applied to any rotating object?

Yes, the precession rate change formula can be applied to any rotating object, as long as its axis of rotation is changing over time. This includes objects such as spinning tops, planets, and even galaxies.

## What units are used in the precession rate change formula?

The precession rate change formula can be expressed in various units, depending on the specific application. Angular velocity is typically measured in radians per second, while time can be measured in seconds, minutes, or any other unit of time.

## How accurate is the precession rate change formula?

The accuracy of the precession rate change formula depends on the accuracy of the input parameters, such as the moment of inertia and external forces. In most cases, it provides a good estimate of the actual rate of precession, but it may not account for all factors that could affect the object's rotation.

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