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Re: [Phys-L] Ex: Re: definition of spring

If you want to be picky — and who amongst us doesn't want that? ;-) —the equator gets more than 12 hours of daylight every day and, at mid-latitude locations in the northern hemisphere, equal day and night occurs 4 or 5 days before the vernal equinox.

John Mallinckrodt
Cal Poly Pomona

On Mar 23, 2021, at 4:45 PM, Larry Smith <> wrote:

Apparently there are various definitions (astronomical, meteorological, etc.).

My colleague thinks the definition of spring hinges on the definition of winter which he would like to define in terms of daylight or temperature: the 91 shortest days or the 91 consecutive coldest days on average. Neither of these allow for spring to start as late as March 21 in the northern hemisphere. He thinks it makes more sense to have the vernal equinox be the middle of spring. While definitions are somewhat arbitrary, why do astronomers say spring _starts_ on the vernal equinox?


On Mar 23, 2021, at 5:39 PM, Anthony Lapinski <> wrote:

I think you meant March 21.

And also ...over the equator at noon.

Interestingly, the equator is the only location that gets 12 hours of
daylight every day of year. My astronomy students every year find this
difficult to understand/explain.

On Tue, Mar 23, 2021 at 7:22 PM Brian Whatcott <>

Astronomical Spring in the northern hemisphere is the vernal equinox -
when the sun is directly over the equator.
Meteorological Spring is counted as the three months following March 1st.
On Monday, March 22, 2021, 06:18:40 PM CDT, Larry Smith <> wrote:

What is the definition of spring (the season) and why?


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