Applegater Spring 2017
7
THE STARRY SIDE
How fast are you moving?
BY GREELEY WELLS
You probably have no idea how
fast you are moving. Even though we
can’t feel it and it doesn’t seem like we’re
moving, and even though we talk about
the sun rising and stars moving overhead,
what’s really happening is the earth is
moving. Fast. Our planet spins at about
1,000 miles per hour and travels through
space around the sun at about 67,000
miles per hour! This orbit around the
sun (sometimes called a solar year) creates
one year on earth.
And here’s something else we don’t
usually think about: Our sun is in orbit
too, through the Milky Way. The sun
travels at about 500,000 miles per hour
as it circles the Galactic Center. One of
these orbits is called a galactic year. Of
course, we—planets, moons, meteors,
asteroids, and comets—are all pulled
along with the sun in this bigger orbit.
Now for some perspective on
distance: Just how big is our galaxy?
Let’s start with the distance between
the sun and the earth. This distance, a
mere 93 million miles, is known as an
astronomical unit. Astronomers use the
astronomical unit as a way of measuring
incredibly big distances in the solar
system. This rather average-sized galaxy
of ours is 100,000 light-years across. (A
light-year is the distance sunlight travels
in a year.) Each light-year is about 63,241
astronomical units. So how wide is our
galaxy? About 586,941,600,000,000,000
(or 600 quadrillion) miles! No wonder it
takes us 240 million years to make just
one circuit around the galaxy.
But wait, there’s more. Our
galaxy is also moving through the
universe. Our closest galactic neighbor,
and the only galaxy we can see with our
naked eyes, is the Andromeda galaxy.
Our Milky Way galaxy is traveling
around 270,000 miles per hour right
This new image style comes from stellarium.org, a great free website that’s like putting a
planetarium on your computer. I can’t recommend it enough! Just plug in your coordinates, and
you can see the day or night sky in 3-D. (My previous love, the Astronomical Calendar by
Guy Ottewell, is no longer being published, but Guy still has many other
wonderful things to experience at universalworkshop.com.)
toward it! In the distant future, the two
will collide, but that’s another story.
Why don’t we feel all this movement?
Because we are all moving at the same
speed. We are speed demons many times
over and don’t feel it or even know it!
As winter sets, spring rises. While
writing this in early January, I notice
Orion way in the west at 3 am, when
I usually rise to meditate, and by dawn
he’s setting. That early morning view is
a glimpse into the next season.
The Big
Dipper has
b e e n l ow i n
Greeley Wells
winter and is
now rising high in the northeast over the
North Star, carrying Leo the Lion with
it even higher in the center of the sky.
The curve of the Big Dipper’s handle is
pointing to bright Arcturus (in Bootes)
and on to Spica (in Virgo, with bright
Jupiter nearby). To the right of Spica is
Corvus, a crow that is a parallelogram.
Next rising in the east is the curved crown
of Corona Borealis; following that, the
hourglass of Hercules. All rise in the east
and move across the spring sky. Or rather,
they appear to rise across our sky! We are
so self-centered it seems it’s the other
things that are moving. But remember,
it’s we who are moving, not the sky.
Other events of note
• March 20 is the equinox, when day
and night are equal. An interesting thing
about the equinox is that the whole world
experiences it in the same way because
the sun rises due east and sets due west
relative to every place on earth.
• By May, bright Vega has risen,
foretelling summer—Vega marks the
first third of the Summer Triangle.
• A couple of spring meteor showers are
worth mentioning. The early morning of
April 2 could potentially yield 100 Lyrid
meteors per hour! With Vega near Venus
(and a crescent moon, which won’t affect
viewing), this will be a glorious morning.
Hope for a clear sky. Then May 5 through
7 in the pre-dawn darkness, face east and
look up for the Eta Aquariids—up to 10
to 20 meteors an hour. The moon will
set just before the prime time.
Here’s to clear, dark night skies and
bright stars for you.
Greeley Wells
greeley@greeley.me