The moon is the easiest celestial object to find in the night sky — when it's there. Earth's only natural satellite hovers above us bright and round until it seemingly disappears for a few nights. The rhythm of the moon's phases has guided humanity for millennia — for instance, calendar months are roughly equal to the time it takes to go from one full moon to the next.
When we talk about moon phases, we are talking about how the moon looks from Earth. Moon phases are caused by the Earth’s orbit around the sun and the moon’s orbit around the Earth. As the Earth orbits the sun, the moon is orbiting the Earth. The moon fully orbits the Earth once every 27.3 days. Moon phases occur depending on how the Sun, Earth, and moon are aligned in the sky.
The Moon's Phases Visualized
“This visualization shows the Moon’s phase and libration at hourly intervals throughout 2015, as viewed from the northen hemisphere. Each frame represents one hour. In addition, this visualization shows the Moon’s orbit position, sub-Earth and subsolar points, distance from Earth at true scale and labels of craters near the terminator."
How Craters are Created
Join Phil for a tour of our capital-M Moon, from surface features, inside to the core, and back in time to theories about its formation.
The Moon and Tides
"Today Phil explores the world of tides! What is the relationship between tides and gravity? How do planets and their moons become tidally locked? What would happen if you were 300km tall? Important questions."
Words to Know
Atmosphere all the gases which surround a star, like our Sun, or a planet, like our Earth.
Crater a hole caused by an object hitting the surface of a planet or moon.
Eclipse the hiding or dimming of one celestial object by another object.
Gravity a mutual physical force attracting two bodies, influenced by the mass of the two objects and the distance between the two objects.
Lunar of, involving, caused by or affecting the moon; from the Latin word "luna", which means moon.
Meteor A shooting star or actually space debris that enters and burns up in earth's atmosphere.
New moon the phase of the Moon when the Moon is lined up between the Earth and the Sun. We see the side of the Moon that is not being lit by the Sun.
Orbit the path followed by an object in space as it goes around another object; to travel around another object in a single path.
Phase the particular appearance of a body's state of illumination, such as the new, full or crescent phases of the Moon.
Satellite a smaller body which revolves around a larger body; a natural or an artificial moon. Earth-orbiting spacecraft are called satellites.
Universe the huge space which contains all matter and energy.
For the full list click here.
How the Moon was formed from Space.com
"After the sun spun to light, the planets of the solar system began to form. But it took another hundred million years for Earth's moon to spring into existence."
This extended article on NASA’s website was published in 1997 and was created in order to help educators teach about space and the universe. The guide was intended for educators of 4-12 grades, however, the information can be adjusted for earlier grades.
Observatories and other resources for the Miami Valley Region. mvas.org
From the moment Neil Armstrong took his "one small step" in 1969, humans have been mesmerized by the moon. Get a crash course on lunar science.