Earth-Moon-Sun System Astronomy

Everything is Moving The Earth, Sun, and Moon are all moving through space Every object we see in the night sky is also moving through space Question: How do the Earth, sun, and moon interact?

From Earth, we watch the moon rise and shine at night, while the sun rises and shines in the day Planets and stars also rise and set The whole night sky seems to move through time

Perspective We see the stars, sun, and moon orbit around us This view is called Geocentrism, meaning “Earth at the Center” The Earth-Moon orbit the sun along with the rest of the planets This view is called Heliocentrism, meaning “Sun at the Center”

Which is Accurate?

The Earth is not at the center Heliocentrism more simply explains what we observe from the Earth The Earth orbits the sun and the moon orbits the earth

Lunar Phases The moon orbits the Earth It completes its orbit in about 27 days We see the moon change in brightness as it reflects sunlight Depending on the position of the earth-sun-moon, we see a different moon phase

Lunar Phases Cont. When the moon is fully lit, it’s called a full moon When the moon is completely dark, it’s called a new moon When the moon is slowly getting brighter, it waxes When the moon is slowly getting darker, it wanes