![]() In the above animation, the plane of the ecliptic is represented by the grey square and the plane of the Moon’s orbit is represented by the blue disk. This means that the Sun, Earth, and Moon lie in a straight line and an eclipse can occur. Credit: Billy TeetsĪpproximately every six months though, the Moon and the Sun are found near one of the nodes – the points where the Moon’s orbit and the ecliptic intersect in our sky. As a result, eclipses do not occur every month. The approximately five degree tilt of the Moon’s orbit relative to the ecliptic results in the Moon rarely being at at a node during the new moon (or full moon) phase. The apparent path of the Sun through Earth’s sky (the ecliptic) is represented by the blue ellipse, while the apparent path of the Moon is represented by the red ellipse. ![]() As the Moon reaches new moon phase or even full moon phase, it will typically appear above or below the Sun in our sky – there is no eclipse. Now imagine these hula hoops together, one sitting inside the other, with one tilted a bit with respect to one another. These hula hoops, however, do not lie in the same plane – the Moon’s orbit is tilted by a little over five degrees to the ecliptic. The Moon does orbit the Earth, so now imagine its path as yet another hula circling the Earth. ![]() For the moment, imagine this path as a hula hoop with the Earth at the center. (This helped give rise to and support the geocentric “Earth-centered” model of the solar system that, up until a couple of hundred years ago, was widely accepted by many as the correct view of our universe.) From our viewpoint on Earth, the Sun appears to follow a specific path in the sky through the zodiac constellations, and this path is known as the ecliptic. From our viewpoint here on Earth that is how things appear. Let’s imagine that the Earth is stationary and the Sun and Moon both orbit our planet. THE OBJECT SIZES AND DISTANCES ARE NOT TO SCALE. The arrangement of the Sun, Moon, and Earth during lunar and solar eclipses. These two moon phases occur every month, so why don’t we have solar and lunar eclipses each month? The answer lies in the Moon’s orbit. As a result, a solar eclipse can only occur during New Moon and a lunar eclipse can only occur during Full Moon. In order for this to occur, the three bodies (Sun, Moon, and Earth) have to be in a nearly perfectly straight line. In general, an eclipse typically refers to the Sun being blocked by the Moon (a solar eclipse) or the Earth blocking the Sun (a lunar eclipse). Most folks will witness at least one partial solar eclipse in their lifetimes however, most folks who aren’t avid amateur astronomers will not witness one of the true splendors of nature – a total solar eclipse.Īn eclipse occurs when one body passes in front of and obscures another body. Solar eclipses are fairly common – there are typically two solar eclipses per year occurring somewhere on Earth.
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