Is there a way to determine the exact time of the vernal equinox in the
exact location where you live. I would assume that since there are time
zones that where you are located in the time zone affects when spring
actually arrives. When I look at sunrise and sunset for the beginning of
spring where I live, they are not equal. Would I just keep looking for
sunrise and sunset, and when they are exactly twelve hours apart in my area
that is the actually beginning of spring.

Thanks

Tom

"mary" wrote in message
...
Is there a way to determine the exact time of the vernal equinox in the
exact location where you live. I would assume that since there are time
zones that where you are located in the time zone affects when spring
actually arrives. When I look at sunrise and sunset for the beginning of
spring where I live, they are not equal. Would I just keep looking for
sunrise and sunset, and when they are exactly twelve hours apart in my
area
that is the actually beginning of spring.


Equinox...
http://www.srrb.noaa.gov/highlights/...lossary.html#e

Equinox calculator...
http://www.stellafane.com/moon_phase/equinox.htm

mary wrote:
Is there a way to determine the exact time of the vernal equinox in the
exact location where you live. I would assume that since there are time
zones that where you are located in the time zone affects when spring
actually arrives. When I look at sunrise and sunset for the beginning of
spring where I live, they are not equal. Would I just keep looking for
sunrise and sunset, and when they are exactly twelve hours apart in my area
that is the actually beginning of spring.

Well, this is rather an astronomical than a meteorological question, but
I'll try to answer anyway. The equinoxes are defined as the very moment
when the centre of the Sun crosses the celestial equator, as seen by a
hypothetical observer placed in the centre of the Earth. By this definition,
it does not depend from the place on the Earth where you live. This year,
it will be at March 20, 12h33 GMT/UTC.

Of course, the centre of the Earth is not really a comfortable place to
live and to observe the sky and the Sun, but when you place yourself at
the surface on the equator, you will see the Sun on the celestial equator
at exactly the same moment. If you place yourself on one of the poles of
the Earth, however, you are about 6,360 km away from the equatorial plane,
therefore due to perspective you would see the Sun (which is at a distance
of about 150,000,000 km from the Earth) at a tiny angle away from the
celestial equator - about 8.75 arc seconds to the south (north) on the
north (south) pole. OTOH, at the season in question, the Sun moves north-
wards in the sky with a speed of about 23'42" (or 1422 arc seconds) per
day, so it will make these 8.75" in less than 9 minutes - which means
from the north (south) pole you see the Sun cross the celestial equator
only 9 minutes later (earlier) which is not a big deal!
If you live neither at the equator nor at one of the poles, you need
to multiply the Earth's diameter by the sine of your geographic latitude
to obtain your distance to the equatorial plane.

The length of daylight is another question. As a matter of fact, light
refraction in the Earth's atmosphere lets the Sun appear a bit higher
in the sky than it is in reality; furthermore the Sun is not a point
but has an appearant diameter of averagely 32' (32 arc minutes), so
the observer on the Earth's surface sees it rise somewhat earlier
and set somewhat later than would follow from calculations not taking
into account these two facts, provided (s)he has an unobstructed view
of the horizon. For instance, at 48° N latitude, the length of daylight
is already about 12h10 on March 20, 2005 and 12h00 daylight are reached
on March 17. For the same reasons, the Sun is still/already visible
24h00 on March 20 at the south/north pole, respectively.

Hope that helps,
Falk

Spring arrives everywhere at same time.

Tarmo Tanilsoo

mary wrote in message
...
Is there a way to determine the exact time of the vernal equinox in the
exact location where you live. I would assume that since there are time
zones that where you are located in the time zone affects when spring
actually arrives. When I look at sunrise and sunset for the beginning of
spring where I live, they are not equal. Would I just keep looking for
sunrise and sunset, and when they are exactly twelve hours apart in my
area
that is the actually beginning of spring.

Thanks

Tom

Tarmo Tanilsoo wrote:
Spring arrives everywhere at same time.

....except for those folks on the other side of the equatorial tracks...
;^)


Tarmo Tanilsoo

mary wrote in message
...
Is there a way to determine the exact time of the vernal equinox in
the exact location where you live. I would assume that since there
are time zones that where you are located in the time zone affects
when spring actually arrives. When I look at sunrise and sunset for
the beginning of spring where I live, they are not equal. Would I
just keep looking for sunrise and sunset, and when they are exactly
twelve hours apart in my area that is the actually beginning of
spring.

Thanks

Tom

So you are going to say that spring starts 12:33 UTC only In Estonia? Not
true! If sun crosses celestial equator and goes to northern celestial
hemisphere, the spring begins. And it happens on March 20th at 12:33 UTC,
next time 365 days 5 hours and 53 minutes later.

Tarmo Tanilsoo
Bob Harrington wrote in message
...
Tarmo Tanilsoo wrote:
Spring arrives everywhere at same time.

...except for those folks on the other side of the equatorial tracks...
;^)


Tarmo Tanilsoo

mary wrote in message
...
Is there a way to determine the exact time of the vernal equinox in
the exact location where you live. I would assume that since there
are time zones that where you are located in the time zone affects
when spring actually arrives. When I look at sunrise and sunset for
the beginning of spring where I live, they are not equal. Would I
just keep looking for sunrise and sunset, and when they are exactly
twelve hours apart in my area that is the actually beginning of
spring.

Thanks

Tom

I think he meant that when spring starts in the Northern
Hemisphere, Fall is starting in the southern Hemisphere

scott

Tarmo Tanilsoo wrote:
So you are going to say that spring starts 12:33 UTC only In Estonia? Not
true! If sun crosses celestial equator and goes to northern celestial
hemisphere, the spring begins. And it happens on March 20th at 12:33 UTC,
next time 365 days 5 hours and 53 minutes later.

Tarmo Tanilsoo
Bob Harrington wrote in message
...

Tarmo Tanilsoo wrote:

Spring arrives everywhere at same time.

...except for those folks on the other side of the equatorial tracks...
;^)


Tarmo Tanilsoo

mary wrote in message
...

Is there a way to determine the exact time of the vernal equinox in
the exact location where you live. I would assume that since there
are time zones that where you are located in the time zone affects
when spring actually arrives. When I look at sunrise and sunset for
the beginning of spring where I live, they are not equal. Would I
just keep looking for sunrise and sunset, and when they are exactly
twelve hours apart in my area that is the actually beginning of
spring.

Thanks

Tom