perigee/apogee

[williowthewisp]

I am trying to determine if the perigee and apogee of the moon's orbit comes on a reliable timeline? is there a fixed amount of time between one perigee and the next or is it variable? What I am trying to ultimately find out is if the perigee and apogee of the moon's orbit would be reflect on a tidal plot record of about a month?

 

 

any help would be appreciated

[Janus]

The Anomalistic month (perigee to perigee) averages about 27 d 13h 18.5 min. I say averages because perturbations can cause this to vary slightly.

 

The synodic month (full Moon to full Moon) averages 29.53 days, bt can vary from 29.18 to 29.93 days for the same reasons. Here's a calculator that will give you the perigee and apogee dates for any year along with the Full and New Moons.

 

http://www.fourmilab.ch/earthview/pacalc.html

 

The extreme high-low tides will occur when Perigee coincides with a new or full Moon. If this happens when Earth is at perihelion, they'll will be even more so.

[Enthalpy]

Stronger tides coincide with Earth's inclination with respect to the Sun's direction, primarily. That is, near equinox - and of course, Moon, Earth and Sun must be aligned.

 

Then you can add considerations about perigee. Beware Moon's orbit is very complicated: its mean distance varies over time, as eccentricity does, and rather quicly (within a human life). Even the orbittal plane does rotate and not slowly. It's a horrible mess.