Little Known Facts About Solar Eclipses

  • The longest duration for a total solar eclipse is 7.5 minutes.

  • A total solar eclipse is not noticable until the Sun is more than 90 percent covered by the Moon. At 99 percent coverage, daytime lighting resembles local twilight.

  • Eclipse shadows travel at 1,100 miles per hour at the equator and up to 5,000 miles per hour near the poles.

  • The width of the path of totality is at most 167 miles wide.

  • The maximum number of solar eclipses (partial, annular, or total) is 5 per year.

  • There are at least 2 solar eclipses per year somewhere on the Earth.

  • Only partial solar eclipses can be observed from the North and South Poles.

  • Total solar eclipses happen about once every 1.5 years.

  • Nearly identical eclipses (total, annual, or partial) occur after 18 years and 11 days, or every 6,585.32 days (Saros Cycle).

  • The Saros Cycle exists because it takes 18 years and 10 days for the entire orbit of the Moon to precess once around in its orbit plane so that the lunar nodes make one complete revolution along the orbit. This "Nordical" period equals nearly an integer number of lunar months (223 x 29.53 days = 6,585.19 days) during each Saros Cycle. Because the true length of the Saros Cycle is 6,585.32 days, you have to wait THREE Saros Cycles in order for an eclipse to repeat at the same spot on Earth.

  • Successive eclipses in the Saros Cycle happen 1/3 of the way around the world from each other, and after three Saros Cycles, the eclipse returns to nearly the same geographic location after 54 years and 33 days.

  • Twelve different Grand Saros eclipse series are now occurring, with the one producing the eclipses of 1937, 1955, 1973, 1991, and 2009 having durations near the 7.5 minute limit.

  • Every eclipse begins at sunrise at some point in its track and ends at sunset about half way around the world from the start point.

  • Partial solar eclipses can be seen up to 3,000 miles from the track of totality.

  • Before the advent of modern atomic clocks, studies of ancient records of solar eclipses allowed astronomers to detect a 0.001 second per century slowing down in Earth's rotation.

  • Total solar eclipses happen because the Sun is near one of the nodes of the lunar orbit, and the Moon is at perigee at this node at the same time.

  • Annular solar eclipses happen because the Sun is near one of the nodes of the lunar orbit, and the Moon is at apogee at this node at the same time.

  • Shadow bands are often seen on the ground as totality approaches.

  • Light filtering through leaves on trees casts crescent shadows as totality approaches.

  • Local animals and birds often prepare for sleep or behave confusedly during totality.

  • Local temperatures often drop 20 degrees or more near totality.

  • During totality, the horizon is illuminated in a narrow band of light, because an observer is seeing distant localities not under the direct umbra of the Moon's shadow.
 


7.5 minutes is the longest duration for a total solar eclipse.


Eclipse shadows travel at 5,000 mph at the poles, and 1,100 mph at the equator.


The width of a path of totality is 167 miles wide.


Local animals prepare for sleep or act confused during totality.

 


Temperatures drop 20 degrees or more at totality.


The horizon glows from distant localities not under the direct umbra.

 


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