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Last Post 10/19/2010 10:44 AM by Nancy Ali

No way !! How do you know???

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Anonymous

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10/19/2010 9:04 AM
How do you know when a solar or lunar eclipse is going to happen? I never understood it!

Tags: solar eclipse, lunar eclipse, archaeoastronomy, eclipses

Dawn Myers

Basic Member

Posts:151

10/19/2010 9:39 AM
Using mathematics. We know the orbit of the earth and the moon and using those known values we can determine when the earth, the moon and the Sun will all be in perfect alignment or when they will be in partial alignment. And using the earth's daily rotation and tilt we can determine where you will be able to see the eclipse.

Nancy Ali

New Member

Posts:17

10/19/2010 10:44 AM
Great question! In the past, predicting eclipses was difficult. People didn't always understand what caused eclipses, so they were often surprised to see the Sun disappear in the middle of the day or watch the moon turn blood red at night. Imagine how terrifying this would be if you didn't know what was going on! Many cultures came up with stories to explain what was happening during eclipses. The Yokut Indians of California explained solar eclipses by saying that Coyote was blocking the Sun.Some cultures calculated the number of days between when eclipses occurred. They used these calculations to predict when future eclipses would occur. The ancient Babylonians observed that eclipses happened in cycles, which we now call the Saros Cycle. The ancient Maya also wrote down eclipse tables in a book now called the Dresden Codex.Today, most people rely on computers to calculate the exact times that eclipses occur. You can check out eclipse schedules yourself at the NASA Eclipse Web Site (http://eclipse.gsfc.nasa.gov/eclipse.html). Knowing some basics about the orbit of the moon around the Earth will let you predict for yourself when eclipses might occur. First of all, eclipses can only happen when the Sun, moon and Earth are directly in a line. This means that the moon must be either in new moon phase (for a solar eclipse) or full moon phase (for a lunar eclipse). But eclipses don't happen at every new or full moon. That's because the moon's orbital path around the Earth is tilted with respect to the Earth's orbital path around the Sun. This means that most new or full moons are not perfectly in line with the Sun and the Earth.For more information about the geometery of eclipses, check out http://www.mreclipse.com/MrEclipse.html.