16 ASTRONOMY • APRIL 2020STRANGE UNIVERSE
Seeing nothing can
be a significant obser-
vation. It may even be
the key to a celestial puzzle.
The most famous example is the
martian canals. When Giovanni
Schiaparelli observed a supersized,
25-arcsecond Mars during its 1877 opposi-
tion, he saw dark lines he thought were river chan-
nels, or canali. After the word was mistranslated as
“canals” and noted astronomers like Percival Lowell
mistakenly confirmed their existence, the public went
nuts. Artificial structures must mean intelligent life!
The idea gained traction after Lowell wrote the 1906
book Mars and Its Canals.
So, a century ago, when several largest-ever tele-
scopes were completed, the world eagerly read the
blockbuster news: no canals. They weren’t there. Yet
the story didn’t end. The May 1938 issue of Popular
Astronomy has a British astronomer’s drawing of the
1937 Mars opposition, complete with distinct canals
and a note saying they were “quite definite.”
The media knew where public excitement lay,
and it wasn’t in the reports of “seeing
nothing.”
That’s why, when I visit a school and tele-
scopically show the Sun using a full aperture
filter, narration is easy when there are lots of
sunspots. But sometimes the Sun is blank; the
mission then becomes how to make a featureless surface
fascinating. How can blankness be cool?
The solution: I explain solar storms and what they
mean, and what the lack of any spots means. So, what
is the Sun doing today? The kids in line excitedly
squirm with curiosity and anticipation. Then each
takes a look and discovers the result. To them, seeing
“nothing” is now a meaningful observation, and a
powerful one.
My very first it’s-not-there experience came from a
Patrick Moore book that I read as a teenager. Listing
double stars, it said Antares has a green companion.
And it did appear green at the eyepiece. But the book
a l so l i sted B et a (β) L ibr ae a s g re en, a nd t hat st a r merely
looked white.
Soon, studying college astrophysics, I realized why
there are no green stars. It’s because green occupies themiddle of the spectrum. For it to visually
dominate, both the red and blue ends
would have to be suppressed,
which can’t happen. (Yellow’s in
the middle of the spectrum,
too, but that color is created by
the mixture of green and red
light, which can easily com-
bine because their ranges
slightly overlap.)
But you can’t get green
from any mixture of colored
light. Those books that listed
green stars were simply wrong. As
for the companion to Antares, the
solution is nowadays widely known.
After looking at the distinctly reddish glow
of the bright primary, the human eye projects a
green afterimage onto any nearby white surface.
Halos around streetlights can be another reality
probe. T he y appe a r i n c er t a i n at mospher ic cond it ions.
Or you may see equally vivid rings if your eyes are irri-
tated after swimming in a pool. Are the rings really
there? Just block out the streetlight with an outstretched
f inger tip. If t he ha lo persists, ever yone is seeing it. If it
abruptly vanishes, it’s not real, but manufactured by
your eye.
Scientists need to be very careful about seemingly
null results. The 1976 Viking landers looked for mar-
tian life by adding soil to a damp, nutrient-rich,
radiation-tagged substance, and later analyz-
ing the resulting gases. On Earth, life alters
it s su r rou nd i ng a i r, l i ke when we ex ha le CO 2.
If there were life in the martian soil,
researchers assumed, it would metabolize
the nutrients and give off gases containing
the radioactive tracer. Sure enough, the air
in the lander’s chamber became radioactive.
Then the lander sterilized a second sample to destroy
any microorganisms. In the subsequent test, the air
didn’t change.
Ultimately, NASA said the tests were negative: no
life. They decided the results came from some strange,
unknown chemistry. But to this day, many others —
including the experiment’s designer and principal
investigator, Gilbert Levin — insist we found life on
Mars back in 1976. (Intrigued? Dig deeper by googling
“labeled release experiment.”)
Martian canals, green stars, and certain halos are
good introductory hallucinations. Send us others and
we’ll dive even deeper into our noble ongoing quest: to
make much ado about nothing.A null result can actually reveal a lot.
In praise
of nothing
Astronomer Giovanni
Schiaparelli produced
this map of Mars
in 1888. On it, he
depicted several
structures he called
canali, or channels,
which were
mistranslated into
English as “canals.”
Notable astronomers,
including Percival
Lowell, later
“confirmed” the
canals, sparking the
idea that martians
had built them. We
now know that the
canals were likely an
optical illusion — they
are not actually there.
GIOVANNI SCHIAPARELLIHow can
blankness
be cool?BY BOB BERMAN
Join me and Pulse
of the Planet’s
Jim Metzner
in my podcast,
Astounding Universe,
at http://www.astounding
universe.comBROWSE THE “STRANGE UNIVERSE” ARCHIVE
AT http://www.Astronomy.com/Berman