Wouldn't the moon technically reach perigee every month? So what produces the appearance of it being any larger or brighter than other times the moon reaches perigee? An orbiting body should reach perigee every single orbital period, which the moon orbits approx every 29 days. So.. ? What gives.
Oh hah just figured it out.
Due to our movement through space, the perigee stays in the same spot, but where the moon must be in its orbit to produce a full moon is constantly changing since the position of Earth is always changing in relation to the moon.
So, say the moon reaches perigee at 4 o'clock on a virtual plane that'll be used for this description. Well, for one orbital period, a visible full moon on Earth will be when the moon reaches 8 o'clock on the plane for that day or two. As the Earth moves through space, the moon will always maintain a perigee at the 4 o'clock position on this plane surrounding Earth. As the Earth orbits the sun, this remains stationary in relation to the Earth but not the Sun, so at some points in Earth's orbital period, the perigee may approach the position required for a full moon, or even end up being directly in line for a lunar eclipse. But at other points, that perigee might just end up being in the position where the moon would create a solar eclipse. That'd be interesting.
So, due to the mechanics of our daily rotation, and our orbital period and that of the moon's orbital period, this doesn't happen all that often I'm assuming. Most likely it comes close to happening every year, but adding in the fact that Earth has a elliptical orbit as well, this wouldn't be as regular of an occurrence, as opposed to if the Earth had a perfect circle, it'd likely happen every year at the same day.
If... I'm visualizing this in my head correctly that is. Multiple stacked orbits can create a messy image in a head, no wonder it took astronomers so long in our history to finally get it correct. 🙂
