Alan Olee Book Report

Not just any moon but the moon; Luna in Latin, Selene in Greek.

The “Near Side” of the moon.   NASA/GSFC/Arizona State University, Public Domain

And this very cool picture is the “Far-Side” of the moon.  NASA/GSFC/Arizona State University, Public Domain

So what’s up with the “near-side” / “far-side” thing?  Well, ends up that one side of the moon always faces earth; another way to think about this is that the moon is rotating at the exact same speed as it is orbiting Earth…got that?  I know it’s kind of weird – but when it comes to orbital dynamics it’s not really all that weird and here’s why.  Orbit happens between two bodies.  If one of the bodies is quite a bit bigger than the other one, gravity will distort the smaller body enough to make it bulge in the direction of the bigger body, hence more gravitation force is applied to the bulge – it’s closer – and this is referred to as tidal locking.  That’s whats happening with the earth – moon system.  Check it out here and there are helpful animations, fascinating mathematical derivations, and so-forth.  http://en.wikipedia.org/wiki/Tidal_locking

Does the far side of the moon ever get sunlight?  Of course it does.  There is no permanent “dark-side of the moon”.

Moon Size and orbit:  its mean radius is 1737.1 km or a bit larger than 1/4 the radius of the earth (0.273 Earths).  Perigee is 362,600 km and Apogee is 405,400 km – only takes about three weeks to get to the moon by rocket ship!  The moon has an orbital period of 27d, 7h, 43.1 minutes.  Its orbit is close to the plane of the ecliptic – meaning it is orbiting Earth roughly in the same plane as Earth is orbiting the sun.  Fun Fact:  All the planets in our solar system orbit the sun in about the same plane – that is one motivation behind the idea that where the planets are today was once upon a time, a long. long. time ago (like billions of years ago) a disk for space junk circling the sun that eventually coalesced into planets.  Or maybe not.  No one really knows for sure; but people are working on the problem and maybe someday we will know for sure.

Our moon is just totally cool – you may have already noticed that though!  It looks completely great – I love it when it’s full, I love it when it’s just a sliver, I love it peering out from behind spooky clouds and I’m camping out alone in the mountains and I just know werewolves lurk under its magical, evil spell.  I hear them howling!  No.  Just coyotes.  But what are those coyotes howling at?  The moon!

The moon is pretty big for a moon.  In fact, it’s bigger in comparison to Earth than any other moon in the solar system except Pluto / Charon but they are way out there on the fringes of the Oort cloud, tiny, and Pluto got demoted from planet status some time ago so they just don’t matter as far as moon/planet ratio.  Here’s a fun and fact-filled chart showing how our moon stacks up against other moons in the solar-system:

Clearly, our moon is world-class!  Although some of those other moons are pretty awesome too – we’ll be discussing them in later blogs.

Here’s a cool video NASA made – it’s largely about the surface and has really great moon picx: https://www.youtube.com/watch?v=2iSZMv64wuU

And here’s another NASA video showing how we get a “blood moon”.  https://www.youtube.com/watch?v=BJJRPFUQfls

Of course there’s a Google moon:  http://www.google.com/moon/  I has handy links to the six manned missions to the moon.  We need to get back there soon…

There will be six supermoons in 2015.  What’s a supermoon you ask?

“… a new or full moon which occurs with the moon at or near (within 90% of) its closest approach to Earth in a given orbit…The moon is full, or opposite Earth from the sun, once each month. It’s new, or more or less between the Earth and sun, once each month. And, every month, as the moon orbits Earth, it comes closest to Earth. That point is called perigee. The moon always swings farthest away once each month; that point is called apogee.  http://earthsky.org/space/what-is-a-supermoon?utm_source=EarthSky+News&utm_campaign=dbd63e6d4e-EarthSky_News&utm_medium=email&utm_term=0_c643945d79-dbd63e6d4e-394199249

By that definition, the year 2015 has a total of six supermoons. The first supermoon, for 2015, will come with the January 20 new moon. The new moons on February 18 and March 20 will also be supermoons. The full moons of August, September and October will be supermoons, too.

Full moon of August 29 at 18:35 UTC

Full moon of September 28 at 2:50 UTC

Full moon of October 27 at 12:05 UTC

The full moon on September 28, 2015, will present the closest supermoon of the year (356,896 kilometers or 221,754 miles). What’s more, this September 28, 2015 full moon will stage a total lunar eclipse, concluding a series of Blood Moon eclipses that started with the total lunar eclipse of April 15, 2014.”  From the link above to the excellent site, Earth and Sky

So keep your chin up, and yours eyes to the heavens and check out the moon.  It’s cool.