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

BAD ASTRONOMY GOES HOLLYWOOD 255
In the special edition of Star Wars: A New Hope, released in
1997, the Death Star explosion at the end (hope I didn’t spoil it for
you) also features an expanding ring. Once again, I’ll defend the
effect: explosions, like electricity, seek the path of least resistance.
Remember, the Death Star had a trench going around its equator.
An explosion eating its way out from the center would hit that
trench first and suddenly find all resistance to expansion gone.
Kaboom! Expanding ring.
We see expanding rings in real astronomy as well. The ring
around Supernova 1987a is a prime example. It existed for thousands
of years before the star exploded, the result of expanding gas
being shaped by gas already in existence around the star. Even
though not technically caused by an explosion, it shows that sometimes
art imitates nature.
10. Yelling joyously, Our Hero flies across the disk of the full
Moon, with the Sun just beyond.
The phases of the Moon always seem to baffle movie makers.
The phase is the outcome of simple geometry: the Moon is a
sphere that reflects sunlight. If the Sun is behind us, we see the
entire hemisphere of the Moon facing us lit up, and we call it a full
Moon. If the Sun is on the other side of the Moon, we see only the
dark hemisphere and we call it a new Moon. If the Sun is off at
90 degrees from the Moon, we see one-half of the near hemisphere
lit, and we call it half full or, confusingly, a quarter moon, since
this happens one-quarter of the way through the Moon’s phase
cycle. This is explained in detail in chapter 6, “Phase the Nation.”
In the 1976 British television program Space: 1999, for example,
the Moon is blasted from Earth’s orbit by a bizarre explosion
(which in itself would be bad astronomy but is later explained in
the series to have involved an alien influence). In the show, we
would always see the Moon traveling through deep space in a nearly
full phase. Just where was that light coming from? Of course, in
deep space there is no light source, which would have made for a
pretty boring shot of the Moon.
Even worse, in movies and a lot of children’s books the Moon is
sometimes depicted with a star between the horns of the crescent.