Bad Astronomy: Misconceptions and Misuses Revealed, from ...

30 BAD ASTRONOMY BEGINS AT HOME
team timidly raises a hand and says, “How about if we say ‘lightyears’
instead?”
It sounds good, I’ll admit. But it’s wrong. And more bad astronomy
is born.
Worse, one Internet service provider even claims it’s “light-years
faster than a regular connection.” They’re using it as a speed!
Not surprisingly, Hollywood is a real offender here. In the first
Star Wars movie, for example, Han Solo brags to Obi Wan Kenobi
and Luke Skywalker that he could make the Kessel Run in “less
than twelve parsecs.” Like a light-year, a parsec is another unit of distance
used by astronomers; it’s equal to 3.26 light-years (that may
sound like a silly unit, but it’s actually based on an angular measure
using the size of the Earth’s orbit). Han’s claim is like runners saying
that they run a 10-kilometer race in 8 kilometers! It doesn’t make
sense. Astute fans of Star Wars may notice that Obi Wan gets a pained
look on his face when Han says that line. Maybe he is wincing at his
pilot’s braggadocio; I choose to think Obi Wan knows his units.
METEORIC RISE
If you go far from the lights of a city on a clear night and wait
long enough, chances are you’ll see a shooting star. The proper
name for it is a meteor. Of course, meteors aren’t stars at all. They
are tiny bits of gravel or dust that have evaporated off the surface
of comets during their long voyages around the Sun. Some are the
shrapnel from collisions between asteroids. Most of them are very
small; an average one is about the size of a grain of sand.
While they are out in space, these specks are called meteoroids.
They orbit the Sun as the Earth does, and sometimes their paths
cross ours. When one does, the little piece of flotsam enters our
atmosphere, and the tremendous pressure generated by its travel
through our air causes it to heat up tremendously, so hot that it
glows. That glow is what we call a meteor. If it impacts the ground,
it’s called a meteorite.
These three names cause a lot of confusion. A meteoroid glows
as a meteor when it moves through the air, and it becomes a meteorite
when it hits the ground. I got into an argument once with a