Our single -- but beautiful moon is approximately 250,000 miles from Earth. (384,400 km). It's diameter is about 1/4 of the Earth's, about 2100 miles across. That’s as far as from New York to Denver, or London to Athens. Not very big! Our moon orbits the Earth every 27.3 days but the phases of the moon (you know, full moon, to new moon, and in between) is just over 29 days. Many cultures on Earth base their calendars on the moon's rotation (these are called lunar calendars). The west bases its calendar on the sun. So the lunar calendar is essentially a monthly calendar, and the solar calendar, a yearly one. (Neither are perfect, and that's why we have leap years and leap seconds from time to time). More on that elsewhere.
The name Moon is an English/Germanic derivation of the latin "menses" which is the cycle women have in their reproductive life. Their cycles are roughly the same as lunar cycles. The first part of the word "Me" is the derivation of early indian/germanic/european words that still exist today. Words, like "month", "Monday", "measure" and "menstrual" - all time related events. Didn't know that did ya?
Obviously people around the world call the moon by different names, the French call it "La Lune" (derived from the latin, "luna"), and is where we brits got the word "lunatic", as for a long time, people thought that a full moon resulted in an increase in human madness. This has been proven wrong in a long statistical study. I am generally just as nuts at other times of the month as I am during a full moon.
The gravitational force of the Earth both keeps La Lune in orbit around us but also keeps it's one side facing us - the gravity of the Earth is so relatively strong that the moon does not rotate around itself like the Earth does (giving us days and nights).
Scientists today remain uncertain about the origin of our moon. For a while, between 1950 and 2000, most scientists believed that the moon was formed when a comet or asteroid hit the Earth during an early period of its formation - now thought to be about 4-5 billion years ago. The asteroid was so large that it's impact broke off a piece of the early Earth and that became the moon. Both bodies (Earth and Moon) reformed over millennia into circular shapes through gravity, internal stresses, earth and moonquakes, etc. There is a ton of information here on what the moon is made of, and interesting differences between the Earth and the Moon.
So, up till 1960, we had eyed the moon with curiosity and, even now, when you see the full moon rise over a river, the sea, or even over a building, with awe.
We completely mistook the different parts of the moon - water and land. We still do not know if there is water under the surface of the moon.
Recently though, as we have explored other worlds and moons with robotic spacecraft, we are discovering that most moons of most planets are completely different from each other. That at least has scientists wondering about the formation of our Solar System including a fresh look at our own moon. How could it have happened that all worlds and moons are different? What do you think? Become a scientist, even a backyard astronomer, and come up with ideas.
There are many discussion groups online at Yahoo and Google, where you can learn and participate in discussions, and see the work that even amateurs are creating such as the images on this page. I really like the people at Yahoo’s Lunar Observing Group and the images they produce. The Lunar and Planetary Institute is also a major resource. Their work is dedicated to the study of our moon and the planets and moons of our solar system. For example, the institute reports on the research of the material brought back to Earth by the Apollo astronauts. Their site is available to all but is has a strong education program for high-school and university students.
A great (but slightly weird) site to really study and learn the names of places on the moon is the “Lunar Republic” which has an online atlas that is easy to use. Just click on the map grid picture. Pick a sector and you will get the lunar details. Hover your mouse or trackpad over an area to get the location names. To get back to the main grid, select somewhere out of the moon image, and right-click (control-click) “back”. Don’t forget to look at the far side and see how different it is from the side we see. Why do you think that is? Tell us something in the forum. When you want to come back here, click “close” at the bottom right corner of the window. See if you can find the Apollo 11 landing site. Clue: D5.
If you do look at the moon, even with your eyeballs, you will see light patches and dark patches. Before we went there and could see clearly, medieval people thought the dark patches were seas, and they named them "Mare" (Sea in Latin). The lighter patches are called "Terrae" like terra-firma which is latin for land. So you can see how we twist our thinking based on what we observe and try to make sense of.
The moon’s phases that I mentioned above are caused by its relative position around to the sun during the month. The moon does not have its own light source, so when its full, there will be more of an angle to the sun. When it is “new” it is in shadow from the sun. We call this waxing (getting bigger) and waning (getting smaller). This site at the US Naval Observatory in Washington DC explains the moon’s phases during each month.
Also, it’s much more interesting to look at the moon through a telescope when it is half full as you will see shadows that give the craters depth. Serious warning: Do not look at the moon through a telescope when it is more than 3/4 full unless the telescope has a filter. It’s very bright and can hurt your eyes.
If you look at the moon through a telescope, or at some of the images on this and many other sites, you will see that the moon is pockmarked with impact craters. If you don’t have a high-power telescope and want to see more detail than shown by the Lunar Republic, there are many images amassed by amateurs over the years. One amazing set belongs can be found on Wes Higgin’s site where you’ll be amazed at what can be accomplished on a limited budget. Wes has a building company by profession, but by night, he’s the man when it comes to showing us our nearest celestial neighbor.
As humans started to leave our planet, first with primitive robotic spacecraft, and later with humans missions and with increasingly sophisticated spacecraft, we got to understand and see the moon close up and learn more about it. On the right is the first image returned to Earth from the far side of the moon. It was taken by a Surveyor Spacecraft in 1966. Click the image to see a full version of the picture.
You also have to understand that in the 1950s and 60's, there was a "Cold War" going on between the West and the Soviet Union, and to a lesser extent with China - a three-way tug. Everyone was afraid of that a war would suddenly break out. It would have been a nuclear holocaust.
Out of this tension, and our new ability to fly in space, the moon was at once, a target to land, and a "high-ground" - a strategic place to launch missiles. So between 1959 and 1973, there was an intense race to “get to the moon” first. Boy, are we dumb sometimes.
But, it gave immense pride to all of the people of the world when Apollo 11 landed on July 20, 1969. In retrospect, a huge amount of our technological society was in many ways born out of these efforts.
The only problem was, we never really thought what we'd do when we got there. Only in the midst of the launch frenzy did the engineers and then the astronauts start to listen to the geologists, and the program began to have a longer-lasting human value.
Between 1969 and 1973, 12 humans walked and drove on the moon collecting tons of rocks for scientific research back on Earth. These lunar rocks are now in research centers and universities around the world. The picture you are seeing below is John Young about to climb into a Lunar Rover, a Jeep-like off-roader that could move at 12 mph and take the astronauts a fair distance from their return spacecraft. When they found an interesting location, they would stop, bag rocks and soil samples, chip bits of other rocks and get back to the shelter of their Lunar Module. The longest stay on the moon - so far - has been four days.
The Apollo program, the culmination of President Kennedy’s mandate to “Before this decade is out, send men to the moon, and bring them back alive” was a scientific success, but was not sustained.
The Russians landed unmanned spacecraft on the moon, including the first images transmitted back home. Included are some of these images.
At the end of the “race”, the Russians and Americans joined forces to make a joint orbital mission - Apollo-Soyuz. We've never looked back, and have had joint missions since then. Simply speaking, the cost to launch people and supplies for a sustained space effort is too much for any one country and we need to work together.
Humans have not been back to the moon since 1972, but plans are underway - by the US, China, Japan, India and a joint Russian-European effort.
In December 2007, a Japanese spacecraft (Kaguya) shot these first HD videos while in orbit around the moon. As this is being written in late 2008, a Chinese spacecraft has completed it’s successful mission orbiting the moon in preparation to send their people - takonauts to the moon, and a spacecraft from India is beginning it’s two-year orbit program around the moon and has landed a probe on the surface.
We will go back, and establish permanent scientific settlements. On the near side, we can reach the moon within a week and return within a few days. We can use that base as a place to build cheaper spacecraft that would not need the huge amounts of fuel to leave the Earth's atmosphere, and can more easily head out to other planets.
Planned for launch in May 2009, the Lunar Reconnaissance Orbiter (LRO) will be sent there to determine possible landing sites, and co-launched with LRO will be an impact study called LCROSS that is a probe that will be hurled into the lunar surface to help determine the composition of the substances below the surface. The amateur community has been asked to provide detailed images for this mission to determine the best impact site.
This is the LRO / LCROSS spacecraft:
On the far side of the moon - sheltered from the light of the Earth, some scientists have come up with the idea of building a massive telescope that would be easily serviceable from the near-side base.