STAR GAZER
THE INTERNATIONAL EDITION
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Horkheimer: Greetings, greetings fellow star gazers. This Friday June 20th officially marks the first day of summer for the northern hemisphere and is called the summer solstice. But just what is the summer solstice anyway? Well to explain we're going to have to go back in time a bit to the first day of spring.
O.K., we've got our skies set up for the first day of spring which is also called the vernal equinox, vernal meaning green and equinox meaning equal night, which means simply that on the equinox the hours of daylight are equal to the hours of night. Now on the first day of spring, the vernal equinox, the Sun rises exactly due east and sets exactly due west. And on each successive day it will rise and set just a little bit farther to the north until the summer solstice, the first day of summer, when the Sun reaches its northernmost point along the horizon and actually seems to stand still and rise and set almost in the same place for a few days. In fact the word solstice means "Sun stands still" which is exactly what appears to be happening.
And as everyone knows the first day of summer is also the longest day of the year, meaning the day of longest daylight and least night. So that's what the summer solstice is all about. But there is more than one solstice. You see after the summer solstice the Sun will appear to reverse its direction and will rise and set just a little bit farther south each successive day. And each successive day the time of daylight will grow just a little bit shorter until the autumnal equinox the first day of autumn when the Sun will once again rise due east and set due west and the hours of daylight will again be equal to the hours of night.
After which the Sun will continue its journey southward rising and setting a little bit farther south each day and daylight will continue to get shorter and nighttime longer until the first day of winter, the winter solstice, when the Sun will reach its farthest point south and will once again appear to stand still, that is solstice, and rise and set at the same place for a few days. And the northern hemisphere will experience the shortest day of the year meaning the day of least sunlight and most night. Then the Sun will appear to retrace its steps and rise and set just a little bit farther north on the horizon each successive day until once again we'll be back where we started on the vernal equinox the first day of spring when the Sun will rise and set due east and west again, completing a yearly cycle which you yourself like our ancient ancestors can observe if you take the time. So this week why not celebrate summer the really old fashioned astronomical way by watching the Sun rise and set at its northernmost points for the year? It's easy and fun! Simply remember that the Sun like birds goes north for the summer and then like the birds heads south for the winter. Keep looking up!
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Horkheimer: Friday June 20th is the summer solstice. But just what does that word solstice mean? To find out let's start with the first day of spring, the vernal equinox, when the Sun rises exactly due east. After which it rises a little bit farther north of east each day until it reaches its northernmost point on the first day of summer, which astronomers call the summer solstice when it will appear to stand still and rise in the same place for a few days. The word solstice is Latin and means "the Sun stands still". So this week the Sun will appear to rise at its northernmost point on the horizon for a few days. Check it out for yourself. Keep looking up!
How did you like this episode?
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* This week's Sky At A Glance
and Planet Roundup from Sky & Telescope.Starry Night Deluxe was used to produce this episode
of Star Gazer
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