THE SOUTHWORTH PLANETARIUM
70 Falmouth Street      Portland, Maine 04103
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43.6667° N    70.2667° W  Altitude:  10 feet below sea level Founded
January 1970
2021-2022: LVI
"A lot of people are afraid of heights. Not me, I'm afraid of widths."
-Steven Wright

THE DAILY ASTRONOMER
Monday, December 20, 2021
How Far Do We Travel?


Heavens above, has the Universe tossed a four pronged spanner into our
works this year. We apologize profusely for these unexpected complications
while offering our uncertain assurance that they'll be no recurrence of
these interruptions in the foreseeable future. Of course, that phrasing
gives us something of an out because, quite honestly, we can't truly
predict what will transpire in a minute from now, so the foreseeable future
simply doesn't exist, except in the rarefied realm of mathematical
astronomy. Yes, you're right: this paragraph is a twitching, stammering,
meandering, this-close-to-sensible Boris Johnsonesque exercise in
incoherent circumlocution. So, in other words, sorry again for being gone
more than I thought I would be. Hopefully, it will be a smooth ride once we
return on Jan 3rd.

Today, we've pulled a question out of Pandora's Jar: that repository of
astronomical queries we keep tucked away in one of the star dome's many
nooks and crannies. This one is particularly interesting as it discusses
how far one can travel through the cosmos during one's lifetime.


*HOW FAR WILL YOU GO?*

* "Hey, DA, let's say I live to be 100. Will I travel more than a light
year through space?" -D. Hartford, Casco*

Well, let's tabulate all the celestial motions we experience. As you
mentioned going through space, we will ignore Earth's rotational motion.
First, then, is Earth's revolutionary motion around the Sun. Although this
speed varies slightly throughout the year as a consequence of Earth's
changing distance from the Sun, our planet's average orbital velocity
approximately equals 66,000 miles per hour. That amounts to 578.6 million
miles per year.
Let's assume you will live to be 100 (one, because we like you and two,
because that number makes the math sweeter.) You will end up traveling 57.9
billion miles around the Sun during your lifetime. Although that distance
is considerable, it amounts to about 1% of a light year, or 3.5 light days.

We next proceed to the solar system, which is whipping around the galaxy at
a considerably faster clip: 143 miles per second, or 514,800 miles per
hour! Over one year, that amounts to 4.5 billion miles! Again, assuming to
live to be a centenarian, you will have traveled 450 billion miles through
space. However, this unfathomable distance equals 7.5% of a light year. Or,
in other words, the distance the solar system traverses in a center at the
speed of 143 miler per second equals about 27 light days.

However, that is not the end of the motions!
Our Milky Way Galaxy, the second largest member of the local group of more
than 54 galaxies, is currently moving toward the Virgo region at 1.3
million miles per hour! This time, we'll take a wormhole through the
intervening mathematical steps and tell you that the galaxy (and you) move
1.13 trillion miles in one century: about 20% of a light year, or 70 light
days.

I should qualify this answer by admitting that it is based on simplified
assumptions. The Sun's motion through the galaxy is hardly linear, it
weaves up and down along the galactic plane and its speed, like that of
Earth, isn't constant.

[image: the-helical-model-our-solar-system-is-a-vortex-hd_hd.original.jpg]

Consider this article to be a back of the envelope response to your
question.  It is safe to say that despite all the rapid celestial motions
we experience, we won't even move a light year through space in our
lifetimes.

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