Solstices and Equinox's

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DaveBone
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Solstices and Equinox's

Post by DaveBone » Wed Feb 24, 2010 12:37 am

I believe that the Spring equinox (vernal equinox) occurs when the sun crosses the earths equitorial plane and is in a certain constellation (which I can't remember). The fall equinox is when it crosses back and also has it's own constellation. The summer solstice in the northern hemisphere occurs when the sun reaches the highest point in the sky and, of course, occurs on the first day of summer. My question is, is that same date called the summer solstice in the southern hemisphere or is it the winter solstice since it is the first day of their winter? The answer seems obvious but also seems that it would be very confusing in the literature since the same name would refer to two different dates.

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Chris Peterson
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Re: Solstices and Equinox's

Post by Chris Peterson » Wed Feb 24, 2010 12:54 am

DaveBone wrote:I believe that the Spring equinox (vernal equinox) occurs when the sun crosses the earths equitorial plane and is in a certain constellation (which I can't remember). The fall equinox is when it crosses back and also has it's own constellation.
The equinoxes occur when the Sun crosses the equatorial plane, regardless of the constellation it's in. It's currently in Pisces at the northern vernal equinox, but that shifts slowly with precession.
The summer solstice in the northern hemisphere occurs when the sun reaches the highest point in the sky and, of course, occurs on the first day of summer.
That is merely a convention in most (but not all) countries. The idea of "first day of summer" has no meaning astronomically.
My question is, is that same date called the summer solstice in the southern hemisphere or is it the winter solstice since it is the first day of their winter? The answer seems obvious but also seems that it would be very confusing in the literature since the same name would refer to two different dates.
We've recently come to accept that not everybody south of the equator is a savage that can be ignored, so political correctness has reared its head <g>. If the names of the seasons are used with equinoxes and solstices, it is best to qualify them with "northern" or "southern". Hence, the northern summer solstice coincides with the southern winter solstice. Also common is to replace the season with the month- e.g. March equinox or December solstice.
Chris

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DaveBone
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Re: Solstices and Equinox's

Post by DaveBone » Wed Feb 24, 2010 2:11 pm

Thanks Chris. A fellow teacher at the school knew I followed the APOD and asked about solstices and I wasn't sure of the answer. I passed your comments on to him and he sends his thanks also
Dave