Applegater Spring 2016
7
THE STARRY SIDE
Imperceptible movement
BY GREELEY WELLS
Let me put you in your car on a
freeway, going as fast as the speed limit.
That book on the seat next to you is just
there, still and quiet, even though you
both are flying though space. Now look
out the window. Things that are close fly
by your fast-moving car. But the farther
away they are, the slower they go by, like
that mountain on the horizon. Look at
the way the sky of stars and even our
moon stay in the same place for long
periods of time while you’re driving at
night! It’s a bit of a weird effect.
How does it work? Those stars
seem to just hang there because they are
unbelievably far away from earth. They
really are moving relative to our spinning
planet: they slowly work their way from
east to west because we are spinning
west to east. But from our point of view,
most of the time they don’t appear to
be moving at all. If you notice a bright
star or the moon moving, it’s because
there’s something stationary right next
to it (like a mountain or horizon line)
to compare it to. So things are moving,
just really slowly.
In a way, this conundrum is
comforting. The world we are a part of
and living on—our home itself—is also
speeding through space, yet we hardly
know it and never feel it. Even though
the stars may be moving at fantastic
speeds, we can’t detect that movement
Illustration: Guy Ottewell’s Astronomical Calendar 2016.
without terrific scientific effort. Even
as we are moving at thousands of miles
per hour around the sun, and all of us
in the whole solar system are tracking at
tremendous speed through our Milky
Way galaxy, all these movements are
undetectable to us. All seems quite
stable and predictable here on earth. It’s
a seemingly safe, knowable, gentle and
beautiful cosmos we live in. There are
so many other more “important things”
to worry about. But let’s appreciate
the luxury of having this curious and
interesting question to ponder. After all,
like the movement of our galaxy, we’re
slowly getting older and rarely notice
that, either!
What a great winter, snow
and all! And Mount Ashland
opened again. Now it begins
to warm up, and those winter
constellations have moved into
the west. Orion stands on the
horizon in April and sinks into the
northwest as the season matures.
With Orion sinks the whole
Milky Way: notice it all along the
northern, western and southern
horizons. In April the Milky
Way rises all along the opposite
southern, eastern and northern
horizons. We live at the edge of
our home, the Milky Way. This
season we’re looking out overhead
away from it. It’s below us and
around us, but not actually in our
clear spring night view.
Leo and the Big Dipper,
parallel to it, have risen high in the
east in March. They will be overhead
in April and westerly in May.
And in May the
constellation
Lyra, with its
Greeley Wells
bright star Vega
of the summer triangle, will be high in
the east heralding summer treats.
With the rising of the Big Dipper
(follow the arch of the handle) is the
very bright Arcturus in the constellation
Boötes. To its east is that crown shape,
Corona Borealis. In April, a little farther
east, rises Hercules, the hourglass shape.
Other events of note
March 20 is the vernal equinox
and the official start of spring. Days and
nights are about equal for a week or so,
and the sun rises due east and sets due
west. I’ve made a mark on my rooftop
star-observation deck railing to show
it. I’m working on marking the other
solar events. I missed the winter solstice
because of endless overcast, but some
day I’ll get it!
Many of the planets have been easy
to see if you’re an early morning, before-
dawn riser. Venus is the main treat, being
by far the brightest. A beautiful little
crescent moon visits very close to Venus
at dawn on April 6.
Second only to Venus is Jupiter,
who’s been rising earlier and earlier with
the constellation Leo. Jupiter has been
living in the constellation Leo for a
year or so, and is now up just about all
night. Jupiter’s solar year is 12 of ours,
so it spends a year in each of the zodiac
constellations—almost imperceptible
movement.
Wishing you clear, dark night skies
and bright stars.
Greeley Wells • greeley@greeley.me
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