Our Epic Little Moon 

     

     Hello, this is Jack on My Epic Blog! Our time exploring the Solar System is running short, so let's go! 

      I bet you want to do far-out exoplanets in the outer reaches of our solar system, but we're staying near home for the time being.  Today's lucky contestant is . . . . the moon!


     Unlike some of the other planets we have studied, everyone has seen the moon.  No need for a picture, right?  Wrong!  The moon is so cool.  Here it is:

                                                                         What a sight! 

     Time to start answering the assigned questions, unfortunately.  So, why is the moon so bright? Well, we all know what the brightest object is, right? It's the sun, bright and shining: 

 

             

     The moon doesn't produce its own light.  The brightness we see is a reflection of sunlight.  So, does that mean the surface of the moon is extremely reflective?  No.  The moon reflects only about 11% of the sunlight that hits it. It’s just that the sun is SO bright that even a little reflection looks very bright to us.

     In the picture of the moon that I’ve shown you above, the moon looks like a perfect circle.  As we all know just from living on this planet, the moon does not always look like that.  

     The moon orbits around the Earth on an elliptical path, and as it does, the light from the sun hits it at various angles.  From our perspective, part of the moon is dark and part of it is lit up.  Since we only see the lit up part, it looks like the moon is changing shapes. It’s really not, of course. 

   

     Here’s a picture showing the various phases of the moon:

 

     You may be wondering how long it takes for the moon to completely orbit the Earth.  At least, that’s the question we’re supposed to answer.  It’s a 27-day journey for our little moon. 

        When the moon is completely lit up by the sun, we call that a “full moon.” It takes 29.53 days for the moon to go from full moon to full moon.  But wait:  Why does it take 27 days for a complete orbit, but 29.53 days from lunar phase to lunar phase?  We’re about to get technical, people!

      Although the moon needs 27 days to circle around the Earth, this is the time it takes for the moon to return to a given position among the stars, and is called “sidereal time.” However, it takes about two more days for the moon to resume the exact same position with respect to the Earth and sun.  This time is called the “synodic month.”  Are we done with this yet?  Good.

     One thing that is really interesting about the moon is its surface.  Why?  Because it contains all kinds of strange things.

    

     The moon’s surface has dark and light areas.  The dark areas are called “maria,” meaning “seas.”  The maria cover about 15 percent of the moon’s surface.  The light areas are called “terrae,” meaning “land.”  They are the bright highlands that cover the remaining 85 percent of the moon’s surface.

    Here's a picture:

  

    The moon is also covered in craters.  These craters are formed when meteors hit its surface.  There’s no atmosphere to protect the moon, so it’s hit almost every day.  Here's an epic picture of the craters:

    The moon’s surface also contains cinder cone volcanoes, “rilles,” which are channels that were probably formed by lava, and lava tubes and old lava flows, which mean that the moon was volcanically active at some point.

     The moon has no true soil because it has no living matter in it.  Instead, the “soil” is called “regolith.”  The regolith is a fine powder of rock fragments and volcanic glass particles.

     I have never wondered how the moon came to be, but apparently a lot of people have because there have been a lot of theories about it over the years.

         One theory, suggested in 1878 by George Darwin, is called the “fission theory.”  Under this theory, what happened was that the Earth spun so fast in its early years that the sun’s gravity eventually ripped off a piece of the Earth.  This piece of Earth became the moon.

     Another theory, suggested in 1909 by Thomas Jackson, is that the moon was a wandering planet that had been captured by the Earth’s gravity. 

    Tired of theories yet?  Another theory was proposed by astronomer Eduoard Roche:  the Earth and the moon were formed independently from the same material that formed all the planets in the solar system.  They just happened to be side by side at the time.

     The leading theory of today, formed in part by the actual exploration of the moon, is that some kind of Mars-sized space body hit the Earth about 4.5 billion years ago, and the resulting debris accumulated to form the moon.  This moon was at first in a molten state, but within 100 million years, it had crystallized, to form what we see now.

     Here are some more interesting facts about the moon:

(1)   The moon has a very thin and weak atmosphere.  It’s called an exosphere.

(2)   The moon has no moons of its own.

(3)   More than 100 spacecraft have been launched to explore the moon.

(4)   The moon is the only celestial body that has been visited by human beings (other than Earth, of course).  

(5)    The moon cannot support life as we know it.

(6)   The moon helps keep Earth’s wobble on its axis pretty stable, which is why we have had a stable climate over billions of years.

(7)    From Earth, we always see the same side of the moon.

(8)    Earth’s moon is called “the moon” because we didn’t know that other moons existed.  Other moons have been given names.

     Thanks for reading my epic blog about the moon.

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