Howdy stargazers and welcome to Star Trails.
I'm Drew and I'll be your guide to the night
sky for the week of November the 2nd through
the 8th. This week we're talking about messages,
the kind we send across the cosmos and the ones
written in starlight. I'll share a quick observation
report before we dive into what's happening overhead
this week. Then in the second half of the show,
we'll turn our gaze from the backyard to deep
space to revisit the Arecibo message, the radio
signal humanity beamed toward the stars more
than 50 years ago. We'll break down what it said,
how it worked, and whether anyone, human or otherwise,
could ever decode it. Before we get into this
week's night sky, I'd like to take a moment to
report on the star party I attended last week.
Last Saturday, my local club was holding their
fall cookout at their dark sky site about an
hour north of where I live. This year, I had
high hopes to get in some serious stargazing.
In particular, I wanted to get eyes on comet
A6 Lemon and maybe even photograph it. We'd had
cooler weather and clear blue skies all week,
but as I made my way to the site Saturday afternoon,
I noticed some ominous haze on the horizon and
high -altitude clouds moving in. Just before
6 p .m., I was welcomed by club president and
friend of the podcast, Mike Roberts, occupying
his important position at the grill. If nothing
else, we'd have a good meal. And it turns out
that may have been the highlight of the night.
Just before 7 p .m. in the fading twilight, I
scanned the sky for lemon with my 11 by 70 binoculars.
Some low -lying clouds finally drifted away and
the comet emerged in my field of view, resembling
a small, very dim, hazy snowball. In the binoculars,
I could detect a hint of a tail. If I hadn't
been looking for it, I could have easily swept
right past it. The only thing that gave it away
was that it looked soft and fuzzy against the
neighboring in focus stars. Having spotted lemon,
I decided to try for a photo. Since I only had
my camera and some normal lenses, it would have
to be a wide field shot. At 70mm on a full frame
camera, it was woefully small, but the coma and
tail were visible enough. I stepped up to 200mm,
and the results weren't much better on single
exposure shots, so I won't be showing these off
anywhere. By then, the clouds were rolling in
around that portion of the sky, so I aimed higher,
catching the Andromeda galaxy in binoculars,
another fuzzy blob at this magnification. The
Milky Way's dim river of light was crossing directly
overhead, with Cygnus the Swan gliding along
its path. We spotted numerous satellites drifting
by, all of them starlings, of course. After about
an hour, the atmospheric haze seemed to multiply
and the sky was looking gray rather than black.
The seeing tanked, so I packed up and headed
home. Sometimes, it seems like these star parties
are cursed, and then there are nights when the
sky is so clear the stars seem to hover just
feet above us. If nothing else, there's food,
camaraderie, and an array of scopes to check
out. If you've ever wondered what a star party
is like, go back and listen to episode 41, where
I combined the sights and sounds of a party into
an immersive first -person report. This week
the moon takes center stage. It begins the week
as a waxing gibbous, bright and nearly full,
and reaches its full phase on Wednesday, also
known as the beaver moon. This one's also a super
moon, appearing a touch larger and brighter than
usual, as it makes one of its closest approaches
to Earth this year. After that, the moon begins
to wane, spending the weekend as a waning gibbous
rising later each night. The moon will light
up the sky all week, so it's not the best time
for chasing faint nebula or galaxies. But if
you're into lunar photography or moonlit landscapes,
these bright nights are perfect. That high -contrast
autumn air makes craters, mountains, and maria
pop beautifully through binoculars or even a
small telescope. As for the planets, Saturn hangs
low in the southeastern sky just after sunset,
shining with a steady golden light. It drifts
southward throughout the evening, setting before
midnight. Jupiter rises later in the night and
commands the morning sky. You'll find it high
in the east -southeast before dawn, bright and
unmistakable. Through a telescope, its cloud
bands and the four Galilean moons are always
worth a look. Venus joins the morning show as
well, the bright morning star gleaming low in
the east before sunrise. It's slowly sinking
toward the sun as November goes on, so catch
it early while it's still prominent. Mercury
is hiding too close to the sun this week and
Mars remains faint and distant, but both will
become more interesting later this year. The
autumn zodiac still dominates the evening. Pisces,
Aries, and Taurus spread out across the southern
sky, while the great winter constellations are
just starting to rise. If you stay up late, look
towards the east and you'll see Orion beginning
to climb above the horizon, a reassuring sign
that the bright winter sky is around the corner.
Coming up, we revisit the Arecibo signal, the
message fired into space more than 50 years ago
as a greeting to intelligent life. We'll take
a look at the format of the message and investigate
if an alien species could even figure out how
to decode the message if they received it. To
find out, we're going to generate our own version
of the message and build our own decoder. That's
after the break. Stay with us. Welcome back.
In our last show, we examined the idea of the
Fermi paradox, the idea that in a universe so
vast, how is it possible we haven't communicated
with any other species? And if you heard the
episode, you might recall that we spent some
time describing one of humankind's attempts to
reach out to extraterrestrial life. Of course,
I'm talking about the Arecibo message. a burst
of binary code sent from Earth in 1974. It lasted
just under three minutes, and though it was meant
for ETs, I've often wondered if anyone could
actually decode it if they received it. That's
the subject of this half of the show. We're going
to take the original binary message intended
for the stars and turn it into audio. Then we're
going to decode that audio in a modern way and
see if we can reproduce the Arecibo signal the
way in which it was intended to be seen. We may
get into the weeds with some jargon along the
way, but I promise I'll try and make it make
sense. First, let's set the scene. The story
begins at the Arecibo Observatory in Puerto Rico.
It's November the 16th, 1974, and the telescope
has just undergone a major upgrade. To celebrate,
scientists Frank Drake and Carl Sagan wanted
to do something audacious. So they decided to
send a message to the stars. Arecibo was the
most powerful radio telescope on Earth at that
time. A 305 meter dish carved into a limestone
valley. It could transmit a million watts at
2380 megahertz, a frequency in the S band far
above radio frequencies we generally listen to.
To send a message into space, the team at Arecibo
used a technique called phase modulation, essentially
flipping the phase or rhythm of a radio wave
back and forth to represent the ones and zeros
of a binary message. We didn't transmit audio
or spoken words into space, just pure data, and
at that time it was the most powerful signal
to leave Earth. The signal's final destination
is the globular cluster M13 in the constellation
Hercules, 25 ,000 light years away. M13 was selected
because it was in the sky when the signal was
scheduled to be sent. Crafted by Drake and Sagan,
the message was a postcard to the cosmos that
said, we're here. When decoded, the signal reveals
quite a bit of information about the human experience,
our science, our genetic makeup, where we are
in the universe, and even more. But could anyone
figure out how to convert the signal to meaningful
data? To try and answer that question, let's
look at what it takes to create such a signal
and how we can use some relatively simple tools
to crack the code. We'll start the investigation
by learning a little more about the signal and
its structure because the key to unraveling it
lies in simple math. The message itself was exactly
1679 bits long. When we refer to a bit, we're
talking about a single on or off state, or in
this case, a one or a zero binary. The number
of bits in the message 1 ,679 was not chosen
at random. It's the result of multiplying two
prime numbers, 23 and 73, and that's the first
key to unlocking the puzzle. If you arrange the
sequence of 1s and 0s into a tall rectangle,
23 columns across and 73 rows down, a picture
emerges. The 0s represent a space, the 1s represent
a graphical block. You could even use a spreadsheet
or graph paper and plot the 1s and 0s into a
23 by 73 grid and see the familiar pattern of
the signal emerge. Any other combination results
in a muddled message. Now let's break down the
resulting image or pictograph from top to bottom.
You've probably seen it in science books since
the late 1970s. The sequence starts with a representation
of the numbers 1 through 10 written in binary.
Below that, the atomic numbers of hydrogen, carbon,
nitrogen, oxygen, and phosphorus, the elements
that form DNA. Then a diagram of DNA's double
helix, with a number showing how many base pairs
it contains. In the center, a little stick figure
of a human next to a bar showing our height and
a number indicating Earth's population in 1974.
It was about four billion people. Beneath that,
a row of nine dots representing the planets of
our solar system, with the third one offset.
That's Earth. And yep, Pluto was still considered
a planet back then. Finally, at the bottom, there's
a representation of the Arecibo telescope itself,
with a coded version of its diameter. The signal
was designed to be so universal that it didn't
require spoken language to read it, just logic
and math. If you've ever read or seen the movie
Contact, which was written by Sagan, you might
recall prime numbers were also used there to
decode a message from the stars. Primes are useful
in this field because they're mathematically
special, not likely to occur naturally as arranged
signals or patterns in nature. Sagan used them
as the logical bearer of meaning before words
or images. Fortunately, we know this going into
our experiment. To see how readable the signal
really is, I decided to recreate it using modern
tools. My weapon of choice is the general purpose
programming language of Python. It's a language
I have some experience with, and the high level
nature of Python means coders have access to
some really advanced functions, such as modules
that do the heavy lifting of signal generation
and analysis. Basically, I set out to create
a software modem to modulate and demodulate the
Arecibo signal. With some lines of Python, I
took the original binary sequence from Wikipedia.
all 1679 bits, and I mapped it to sound. I decided
to use a protocol inspired by my ham radio experience,
frequency shifted keying, or FSK. With this technique,
I assigned specific audio frequencies to the
ones and zeros. In this case, 1200 and 1800 hertz.
It's essentially the same principle ham radio
operators used in digital modes like radio teletype.
To match the data rate of Arecibo, we're encoding
at 10 bits per second, which results in a transmission
of just under three minutes in length. Finally,
the script outputs the binary stream as a WAV
audio file that can be played on just about any
device. At this point, our result is similar
to the signal sent from Arecibo with a couple
major differences. Since we're shifting between
two audible frequencies, we've essentially sonified
the raw data so that we can now hear it. Remember,
the Arecibo message simply shifted the phase
of a carrier wave to represent the data, so there
wasn't much to actually listen to in the original
transmission. For fun, I recreated the phase
shifted version and it basically just sounds
like one continuous tone. But to hear that tone,
I had to lower the frequency by magnitudes. The
Arecibo signal was sent at a frequency that is
millions of times, no joke, millions, higher
than what we can hear as humans. To explain it
another way, for any musicians out there, check
this out. To make the original Arecibo signal
audible, we're reducing it in pitch by about
1 .2 million octaves to bring it into the range
of human hearing. As a result, our version sounds
like a stream of robotic chirps and pulses. I
could actually send it out into the ether with
my ham radio transceiver if I wanted to, and
someone could, in theory, decode it. They would
need to understand the protocol, in other words,
my data rate and how the data is structured once
received. Essentially that 23 by 73 grid that
I've mentioned. So to complete the circle, let's
decode the message using another Python script
and see if we can translate the audio data into
the familiar visual of the Arecibo pictograph.
We need to first load up the audio file for analysis,
and fortunately Python contains libraries that
do just that. Knowing the data rate of 10 bits
per second, we segment the audio into windows
of one -tenth of a second. For each window, we
measure the energy of those two tones. Whichever
frequency is stronger, either 1200 or 1800 Hz,
becomes that bit's value, a 1 or a 0. Presumably,
an alien species could analyze the message and
see there is patterned information that appears
in regular intervals. If you load up our wave
file into an audio editor like Audacity, you
can zoom into the waveforms and actually see
the alternating tones. When you string these
bits back together, you get the same binary sequence
that left Earth in 1974. Using a graphic library
in Python, we can plot the binary values into
that 23 by 73 grid and pop out the resulting
image as a PNG file. And there it is, the Arecibo
message with its familiar DNA helix, stick figure,
and radio dish perfectly recreated. If you'd
like to try this for yourself, I'll make my code,
WAV file, and resulting graphics available in
the show notes. You'll need Python installed
on whatever computer you're using. I'm using
Linux, but Python runs on everything from Windows
to Mac OS to systems on chip like the Raspberry
Pi. So encoding and decoding the Arecibo signal
is actually somewhat straightforward, but only
because we already knew how it was constructed.
Assuming an intelligent civilization made it
this far, would they even understand what they're
looking at? Can we as humans even understand
it? A viewer would see the geometric shapes,
stripes, dots, the stick figure of a human, but
would you recognize the bar next to the human
indicates its height in binary? Would you recognize
that those five lines of dots are atomic numbers?
Would you know the twin spirals are DNA? Even
for us, the meaning only emerges because we already
basically know the story. We know what DNA looks
like. We know what a solar system looks like.
We know what a human is. Maybe some folks even
know how to convert binary to the familiar numbers
of a base -10 system. An alien species wouldn't
share those references. They might not even perceive
visual patterns the way we do. Maybe they'd interpret
the entire thing as a mathematical proof or a
piece of music or a coordinate map. Or maybe
they wouldn't recognize it as a message at all.
The Arecibo pictograph looks self -explanatory
to us because it is us, and that's the trap.
It's anthropocentric. It's written in the language
of human experience, dressed in the symbols of
universal truth, yes or no, on or off. So imagine
you're the one receiving it. an alien scientist
staring at a stream of data from the sky. How
would you even begin? Maybe you notice a repeating
pattern of phase shifts. Okay, maybe that means
it's digital. You count 1679 bits. You somehow
realize that's 23 times 73, both prime numbers.
You try arranging the bits. Maybe you find the
right orientation and maybe not. And if you do,
you're still faced with a puzzle made by a species
you've never met, living on a world you've never
seen, with no shared biology or shared reference
frames. It's like solving a crossword puzzle
in a language that doesn't exist. And maybe this
works both ways. Maybe we've already received
messages like this and we didn't recognize them.
We've detected fleeting, unexplained radio bursts,
like the famous wow signal, and fast radio bursts
that repeat and vanish. Maybe those are natural,
or maybe they're messages encoded in forms we
can't yet decipher. SETI scientist Paul Davies
once said that an alien transmission might be,
quote, hidden in plain sight, a pattern so subtle
we mistake it for noise. And Jill Tarter reminded
us that if the universe is speaking to us, we
might not recognize the language. The Arecibo
message was meant to say something about who
we were and what we could do. It was an act of
optimism, a beacon of math and meaning beamed
into the dark. Even now, more than 50 years later,
that signal is still traveling outward at the
speed of light, racing across the space between
stars. Long after our voices fade, that signal
will keep going, like a perfectly preserved artifact
of curiosity and intelligence. Maybe someday
someone will catch it, maybe they'll rearrange
the bits and see the shape of a human, and maybe
they'll wonder who we were. or maybe they'll
see nothing at all. The Arecibo message was just
the beginning. Since 1974, we've sent a handful
of others, each one a new experiment in interstellar
communication. In 1983, Japan's message to Altair
carried digital greetings toward a nearby bright
star. In 1999 and 2003, the Cosmic Call 1 &2
projects transmitted more elaborate self -describing
data sets toward multiple Sun -like stars. Later
came the Teenage Message in 2001, a musical broadcast
created by Russian students, and NASA's 2008
Across the Universe signal, which beamed a Beatles
song toward Polaris. That same year and into
2009, messages such as a message from Earth and
hello from Earth targeted the potentially habitable
world Gliese 581c, carrying thousands of short
notes from people around the globe. Each attempt
has been part scientific demonstration and part
act of faith. Whether these signals ever reach
another mind is unknown, but together they form
a faint chorus of intent. Evidence that at least
once and then again and again a small species
on a small planet looked up and tried to say
hello to the universe. It's funny how the things
we love sometimes circle back and meet each other.
For me, astronomy, ham radio, and music always
felt like separate pursuits. One is about the
stars, one is about radio waves, and one is about
sound. But when you start listening closely,
you realize they're all part of the same language.
I had a lot of fun making this one, but producing
episodes like this requires a good bit of time
and even more caffeine. If you found it interesting,
please share it with a friend who might enjoy
it. The easiest way to do that is by sending
folks to our website, StarTrails .Show. And if
you want to support the show, use the link on
the site to buy me a coffee. It really helps.
Be sure to follow us on Blue Sky and YouTube.
Links are in the show notes. Until we meet again
beneath the stars, clear skies everyone.