*THE SOUTHWORTH PLANETARIUM*



*207-780-4249 <207-780-4249>       www.usm.maine.edu/planet
<http://www.usm.maine.edu/planet> 70 Falmouth Street  Portland, Maine 04103
43.6667° N,                    70.2667° W Founded January 1970*

*             "In the popular belief, most astronomers end by losing their
minds."*


*                            -H.L. Mencken (1880-1956)*




*THE DAILY ASTRONOMER*

*Thursday, May 5, 2016*
*Weather vs. Astronomy*



*We did promise to address at least two Pandora inquiries each week.
Yesterday, we only answered one, as the response was quite involved.
Since tomorrow we have our weekly quiz, today is the only time when we can
answer the second question this week.       Now, one might think that we
just wrote this question under an assumed name for purposes of
self-flattery, but we assure you this query came to us from an outside
source.    It pertains to the comparative accuracy rates of meteorologists
and astronomers.     *


*"I am an avid sky watcher and I am a weather nut.      I noticed that the
predictions of weather forecasters are often wrong, but astronomers always
get their predictions right.    Why are astronomical forecasts so much more
accurate than weather forecasts?"*
*      -Rob W,  Skowhegan*



*While this question presents us with a beautiful opportunity to coat
astronomy in four layers of glory, we will instead be quite charitable.*

*The simple reason that weather forecasts are sometimes less accurate than
astronomical ones is that the astronomer contends with far fewer
variables.  For instance, in the solar system, the mass difference between
the Sun and planets is so great that one could consider planetary motions
to involve nine two-bodies problems, those that can be solved exactly.   *
*The meteorologists have to deal with air parcels that have different
pressures, temperatures, humidity levels, and even compositions.   These
parcels react with other air parcels while the Sun shines at different
intensities along a planet whose surface consists of variegated patches of
materials that radiate and absorb heat at different rates.  *
*Earth's weather system is a sub-chaotic system, meaning that precise
predictions are not possible.   You might have heard of the "butterfly
effect," the notion that a butterfly flapping its wings in Brazil might
cause a tornado to form in Kansas.  This fanciful statement merely means
that meteorologists cannot account for every single air parcel because, for
one thing, they can't measure the conditions of each one and two, these
measurements, themselves, are limited.   *

*​*


*Of course, astronomical predictions are also limited.    Even though
astronomers can accurately predict eclipses and planetary positions tens of
thousands of years into the future, there comes a time when the predictions
become uncertain.    We cannot tell you the specifics of eclipses or
planetary positions a million years from now.   There is a measure of
uncertainty in solar system dynamics that precludes astronomers from
knowing conditions indefinitely in the future.     However, since
astronomers deal with fewer variables, these errors won't become
troublesome for quite a while.*
*P.S.   I hope the meteorologists on this list-serve do not feel slighted
by this article, which we wrote with the type of exuberant joy that three
straight weeks of dreary weather invariably engenders in people.  *