What Do We Really Know About The Moon?

Emanuel Swedenborg, Immanuel Kant and Pierre-Simon Laplace in the 18^th century about the presence of our solar system, of which the moon is an integral part, is that it began its formation about 4.6 billion years ago when a smaller section of a very large molecular cloud collapsed due to the influence of its own gravity. Part of the smaller collapsing portion then gathered in the center forming the sun while the planets with their moons, the asteroids and any other bodies known as smaller solar system bodies (SSSB) were formed from the remaining mass of the breakaway cloud. As subsequent observations have occurred, the original theory has been refined to include more information now available about exoplanets which are bodies outside of our solar system. According to a posting in J. Sneider’s “Interactive Extra-solar Planets Catalog” in The Extrasolar Planets Encyclopedia, as of 1 February 2024, there are 5,606 confirmed exoplanets in 4,136 planetary systems with 889 systems having more than one planet.

Much of the foregoing information has been gleaned as a result of space age exploration and it is known that our solar system has evolved significantly since it first began to form. It is interesting though that the concept of the sun being the center of our world and the idea of the earth orbiting around it was offered by Greek astronomer and mathematician Aristarchus of Samos around 250 BC but the theory was not accepted until the late 17^th century. Actually, according to “Solar System” in the Merriam Webster Online Dictionary 2008 the term solar system wasn’t recorded until 1704.

So we accept that the sun is the center of our universe and everything else revolves around it – but what about the moon, specifically Earth’s moon? It is known that many of the moons associated with other planets were derived from circling discs of gas and dust that surrounded their parent planets while others formed independently and are later locked into orbit by their planet. But how did Earth get its moon? Aware that the solar system evolved to its present state as a result of continuous collisions between orbiting bodies,  Canadian geologist Reginald Daly in 1946 proposed the giant impact hypothesis (also known as the Big Splash or the Theia Impact) which suggests that approximately 4.5 billion years ago Earth collided with a dwarf planet similar in size to Mars that was in the same orbit and that the particles resulting from the impact formed together to create the moon – a process known as accretion and responsible for formation of most astronomical objects. A point of interest is that the dwarf planet involved in the collision is known as Theia named after a mythical Greek Titan and mother to Selene, the Greek goddess of the Moon.

Although currently less frequent, impacts are thought to have been a regular happening during the  formation of the solar system. Evidence of early collision activity results  is very apparent in the northern Arizona desert where one will find a meteorite crater that resulted from a collision occurring some 50,000 years ago. Mining engineer, Daniel Barringer, owner of the Standard Iron Company, purchased the crater site and surrounding land during the early 20^th century and began a search for iron ore that he believed was left behind after impact. It was then known as the Barringer Crater but had several previous names given it when it was first discovered in the 19^th century by American settlers. After spending his fortune in the search, Barringer found no iron but rare forms of silica (coesite and stishovite) were discovered at the crater site and a short distance away at Canyon Diablo. These findings were reported in Eugene Shoemaker’s 1974 book, Guidebook to the Geology of Meteor Crater, Arizona, adding to the evidence that the impact essentially vaporized the impactor meteorite which broke away from the main body both before and during impact.

Much has been learned about the moon, earth’s only natural satellite, since its accretion, both prior to and since the first hard landing of an unmanned spacecraft (Luna 2) carried out by the Soviet Union in September 1959. Most of us at one time or another have heard of the dark or far side of the moon but it is the light side which always presents itself to Earth, and until recently was the only side where soft landings had occurred. A hard landing is when the craft intentionally crashes into the moon’s surface as did Luna 2 but a soft landing allows the crew to land, leave the craft, explore and then return the spacecraft safely to Earth. Since the historic July 1969 soft landing of Apollo 11, the first manned spacecraft accomplished by the United States, there have been five additional crew manned landings from the U.S.,  the last one departing the moon’s surface in December 1972. In January 2019 China carried out an unmanned soft landing on the moon’s dark side. 

Moon exploration has given us an idea of its composition and appearance and we know that it orbits almost 239,000 miles away from Earth and its mass is about 1.2% of that of the Earth’s. The moon’s surface has mountains and craters and is covered with lunar soil which is the result of billions of years of bombardment of its surface rock by charged atomic particles, some originating from the sun. Mostly on the near side of the satellite they have found dark maria or seas made up of the cooled magma resulting from the molten lava that flowed through ancient impact areas. Moonlight is the result of illumination from the sun and the continuous shifting of its position during orbit coupled with its angular shape produces the various moon phases observed from Earth. And, in addition to the subject of spaceflight let us not forget how the moon as a subject of influence plays a big part in art, mythology, natural sciences, religion and time.

Over the years telescopes of many types have played a major part in exploration of the skies and visiting an observatory allows one to view the stars, planets and galaxies much better than could be seen from one’s backyard.  Beginning in 1965 space telescopes, which are essentially astronomical space observatories, were launched, some designed specifically for frequency ranges with others designed to detect microwaves, radio waves, gamma rays, X-rays, etc. The space telescope, Hubble, since its launch in April of 1990 has, during its more than thirty years of operation, delivered amazing images of astronomical objects including stars and galaxies. And recently the James Webb space telescope, developed in a partnership led by the National Aeronautics and Space Administration (NASA) with the European (ESA) and Canadian (CSA) Space Agencies, was launched December 2021. The Webb is designed for observation and analysis of astronomical objects and can detect objects up to 100 times fainter and those considerably older in cosmic time than Hubble can. It is expected that the Webb will discover more about exoplanets to include their makeup, environmental conditions and potential for life.

Can you see where all this exploration is headed? It is estimated that in around 5 billion years the sun will grow outward many times over to become a red giant star that has exhausted its supply of hydrogen and begun thermonuclear fusion of the remaining hydrogen and will start to cast off its outer layers to become one of the eight currently existing  in the solar system and 10 billion white dwarfs in the milky way galaxy. Following that it is expected the gravity of erratically orbiting stars will reduce the planets orbiting the sun with some being ejected into space while others will be entirely destroyed until there are no more planets orbiting.

That would mean that the estimated life span of the solar system and its sun, moon, planets, and other astrological bodies floating around in space is about 10 billion years from the beginning of its formation to its demise. Hopefully not happening today, tomorrow, next month or next year so we might as well plan on viewing the total eclipse of our sun. It is estimated that the eclipse should start in San Antonio at 1:34 pm when the upper edge of the moon touches the lower edge of the sun and is complete at 2:21 pm when the remaining lower edge of the moon departs from the upper edge of the sun. taking between 81 and 90 minutes total to complete. The temperature will cool somewhat as the heat from the sun will be totally blocked at full eclipse, This is the first time in many moons that the eclipse has been visible in this area so enjoy but follow directions and do not look at the sun at any time without the special glasses!