Sky and Telescope - November 2017 - 6

FROM OUR READERS
By the way, my article mistakenly states that
both M31 and M33 are moving toward us -
but only M31 is doing that.

Wishing for the Moon
While looking through my archives I
found the Sky & Telescope issue from
September 1992. The cover story, by
Paul Lowman, Jr., was a lengthy "letter"
written from a lunar base on November
16, 2017. (In one of the letter's illustrations, on page 262, the author is gazing
at the Moon's shadow on Earth during
August 21st's solar eclipse.) As I ﬂipped
through the article, I was impressed -
but sad at the same time - that a dream
of establishing a lunar base has not yet
become reality.

Sounds from Meteors
Regarding the origin of sound with
meteors (S&T: July 2017, p. 12), an
alternative explanation is the common
phenomenon called synesthesia. This is a
neurological process whereby the brain
converts one type of sensory input into
another. By the way, I heard my ﬁrst
meteor one early January morning while
out on my paper route.
Craig Hohm, M.D.
Penn Yan, New York

Andy Rokita
Wilmington, Delaware

Pass the Pasta

I've noticed that astronomers tend to
play up the chances of ﬁnding life elsewhere (S&T: Sept. 2017, p. 38) because
of the sheer number of potentially habitable planets in our galaxy and the detection of the organic molecules required
for living organisms. The numbers
certainly look good, but as a molecular
biologist I am more pessimistic.
Even the most primitive bacterium
is vastly more complex than a mixture
of its component chemical molecules.
Its sophisticated system for information storage and transfer is prone to
just enough error to allow evolutionary processes to occur. The probability
of ﬁnding even these simple life forms
elsewhere is tiny, in my view, leaving aside the (quite plausible) issue of
life on Earth having been seeded from
another part of the solar system.
If we combine this tiny probability
with an even smaller chance of multicellular plants and animals evolving,
let alone the emergence of human-like
intelligence, then things don't look so
good. I therefore urge astronomers to
be more grounded (pardon the pun) in
biochemical reality - but of course to
keep looking for the evidence that will
support or demolish these speculations.
Ed Zanders
Cambridge, England

N O V E M B E R 2 0 17 * S K Y & T E L E S C O P E

Robert Gray mentions how he and his
team adjusted the hydrogen emission
frequencies they searched to allow for
the blueshift caused by the Andromeda
Galaxy's relative motion toward us.
Shouldn't they have bracketed those
frequencies in both directions to allow
for the possibility that the transmitting
race might have already compensated
for that motion, so that the broadcast
would be received here as the usual atrest wavelength? If the senders were as
advanced as assumed, surely they would
have thought of that.
Dan Heim
New River, Arizona

Robert Gray replies: To cover the
possibility that signals aimed at our
part of the Milky Way were Doppler-adjusted
to arrive at the hydrogen rest frequency, we
observed in a 125-kilohertz-wide spectral
window, which seemed sufﬁcient to cover
various uncertainties. With 8,192 channels available, it was then possible to use
channels only 15 Hz wide. And if the signals
weren't Doppler-adjusted, we also picked
a center frequency for our receiver to compensate for the motions of the two galaxies
with respect to us and for motions across
their disks. Our spectral windows also partly
covered some other possibilities, such as
signals adjusted to fall at hydrogen's rest
frequency at the center of the Milky Way.

Carl Masthay
St. Louis, Missouri

Whither Helium?
A note about the discovery of helium
(S&T: July 2017, p. 30): Jules Janssen and
Norman Lockyer independently realized
that one could observe the spectrum of
the Sun's chromosphere without waiting
for an eclipse by using two spectrographs
(and they share a joint gold medal from
the French Academy of Sciences for
this). But Lockyer alone recognized the
anomalous spectral line near sodium's
strong D emission. There's a whole book
about this saga, Biman Nath's The Story
of Helium and the Birth of Astrophysics,
and a very good book it is, too.
Virginia Trimble
Irvine, California

Dark (and Mysterious) Matter
Thanks, Leonidas Moustakas, for using
one exclamation point in particular in
your 8-page article on dark matter (S&T:
Aug. 2017, p. 28). While exploring the

SK Y & TELESCOPE

Life Among the Stars?

Just to be a bit persnickety, I'd like to
point out something about the scientiﬁcally great picture titled "Pan: Saturn's
Ravioli-Shaped Moon" (S&T: July 2017,
p. 13). Hmm, ravioli is the Italian plural
of raviolo ("little turnip"), so Pan is
actually a "raviolo-shaped moon." But,
hey, I don't blame David Dickinson -
how many persons would know that?
Meanwhile, I also got to read about
"nuclear pasta" on page 19!

Sky and Telescope - November 2017

Table of Contents for the Digital Edition of Sky and Telescope - November 2017