Everyone recognizes the Moon, visible with the naked eye and looming large in the sky when full. A beautiful orb bathed in the Sun's light and reflecting it back to us on Earth as a silvery glow. Some people see "the Man in the Moon" and others see the "Rabbit". However you see it, the Moon is beautiful.
Under the Full Moon, lovers walk hand-in-hand. Mariners depend on its gravitational pull to raise or lower the tides of the oceans. Nocturnal animals move in its light and feed. The Hunter's Moon during October allowed hunters of old to use it's light to hunt fattened deer in the late part of the year. In September and some times October, farmers used the Harvest Moon to work all night under its light to harvest crops. The Blue Moon, as we all know, is not blue. It is merely the second full moon, should there be two full moons in any given month (with the exception of February). The cycle from New Moon to New Moon is 29 days, 12 hours, 44 minutes, and 2.8 seconds (known as a Synodic Month). February has 28 days and only in a leap year does it have 29 days--still not enough days to qualify for a Blue Moon.
Ancient cultures reasoned the rhythm of it's cycles, with great precision. It is, after all the first and second largest object in the universe from our vantage point on Earth. Only the Sun competes with its size. The Moon has two primary positions in space: Perigee and Apogee--the minimum distance and maximum distance as the Moon travels on it's elliptical path around the Earth. Sometimes the Moon is larger and sometimes smaller than the Sun. Astronomers measure all objects in the Universe by angular measurement. At Perigee, the Moon is 356,400 kilometers from Earth and at Apogee it is 406,700 kilometers from Earth. The angular measurement for Perigee is 33' 28.8" arc minutes, and at Apogee the angular measurement is 29' 23.2" arc minutes. The motion of the Moon and where it is when it obscures the Sun during an eclipse determines if an eclipse of the Sun will be a Total Eclipse or an Annular Eclipse. Review our photo gallery page under observations, and you will see a photo of an Annular Eclipse of the Sun. Note carefully that the Moon does not completely cover the Sun's disc and that there is a ring of sunlight extending past the Moon's darkened disc. You will notice in this image that the sunlight is irregular and broken. You are observing Baily's Beads--the light that is irregular and broken is caused by the Sunlight shinning through the mountains and valleys of the Moon's outer edge.
Have you ever noticed the surface of the Moon? It always appears the same throughout your whole life on Earth. It is unchanging. We here on Earth only observe the near-side and never the far-side. Our Moon is in a synchronous rotation around Earth and always presents the near-side to us on Earth. One would think that if this is the case, we can only observe 50% of the Moon's surface of the near-side. In reality, the complexities of Lunar Dynamics offer us on Earth a little more to observe than just the near-side. The slender "crescents" of the averted hemisphere are brought into view by oscillating or swinging motions called "librations." These librations occur in both latitudes and longitudes, simultaneously and continuously, and their combined efforts bring into view the peripheral area called libration zones. The Moon and the Earth are both massive "gyroscopes," and both maintain spatial orientation. Both point to the same position 'on the sky' no matter where they are in orbit. The end result of this libration action is that we can observe 57% of the Moon's surface.
As everyone knows, we have walked on the Moon. A total of twelve humans have stepped onto the Lunar soil, called Regolith. The Apollo missions were a success. Science truly advanced. New knowledge was gained. The missions were expensive but well worth the money. Scientists are planning a habitat for humans to live on the surface of the Moon in the future. It will not be an easy task, and it will be costly. Great science must prevail to accomplish this event, but in the end, it will happen. I suppose that the humans living on the Moon in the future will gaze at the Earth and marvel at its uniqueness as both orbs travel through space in a delicate balance.