25th Apr 2007
Originally posted at www.seti.org/general/ao_message_crop.html
and still available in
Is the Latest Crop Circle a
Message from E.T?
Crop Circles. Undoubtedly you're aware of these intricate patterns
carved in the wheat fields of (mostly) England.
But could they be
signals from visiting aliens?
Despite the fact that many of the
circles are known to be the work of pranksters, interest in crop
enjoyed a recent revival thanks to a pair of new
patterns that appear in a field next to the Chilbolton Observatory
in Hampshire, England. One is of a face, and many say that it looks
like the archetypal "gray" alien so often seen in films and
The second is a modified version of the 1974 Arecibo
message, broadcast in the direction of the globular cluster M13 in
November of that year.
The Arecibo message, which was designed by
Frank Drake (who was then
Director of the Arecibo Observatory in Puerto Rico, and is now
Chairman of the Board of the SETI Institute) together with his
Observatory staff, was a simple graphic consisting of 73 rows of 23
"bits" per row. This number of rows and columns was chosen because
each is a prime number. Prime numbers could be easily guessed by any
recipients, and that would help them to decode the graphic.
message was sent by simple shifting of the signal between two
frequencies in the 2,380 MHz band. It took three minutes to send the
The message itself gives the kind of information that any culture
would want to learn about us:
where we are located (at least within
our solar system)
what we look like (a crude stick figure)
simple drawing of the telescope used to send the message
something about our biological construction (DNA and some of the
building blocks of our biochemistry)
This message was sent as a
"demonstration" to commemorate the upgrading of the 1,000 foot
diameter Arecibo telescope with a new, more accurate reflector
The crop circle found in Hampshire looks very much like the one
broadcast in 1974. But there are some differences: the Hampshire
pattern has replaced the Arecibo Telescope with another graphic that
is reminiscent of a space satellite with solar cells.
that depicts our solar system has been replaced with another that
still has nine worlds, but planets 3 through 5 are offset, and the
last is drawn larger than the others (or perhaps this is a depiction
of the four Galilean moons of Jupiter). Finally, the graphic of the
human has been modified by a stick figure that, while humanoid, has
a far larger head.
Good fun, and a nice example of grain graffiti. But some folks think
that this crop circle (and at least some of the more than a thousand
other circles that have appeared in the last decade) are truly
signals from visiting aliens.
The aliens, in this view, have
borrowed an idea from
Carl Sagan's "Contact," and initiated
communication by returning one of our own signals to us (albeit,
This is highly improbable. There is no evidence to suggest an
other-than-earthly origin for these graphics.
Some of the reasons
why we are skeptical that this is a "signal" from afar are as
The aliens, if they've received this signal, would obviously be
aware of our capability to send and receive high-frequency radio.
After all, they would only know of the 1974 transmission by
receiving it. And, of course, they've made a point about radio by
leaving their message next to a radio antenna. So why would they
resort to an extraordinarily crude method of "replying" - carving
simple messages in our wheat? Why don't they use radio?
graffiti only conveys a handful of information - roughly the
equivalent of a few sentences of any text. They could convey far
more, in a matter of seconds, by radio. If radio isn't their thing,
why don't they simply leave a copy of the Encyclopedia Galactica on
the doorstep of either the farmer or the radio observatory?
could arrange for a radio blast sufficiently powerful to reach every
FM or TV set in a hemisphere, which would quickly convey far more
information, and to everyone at once. After all, if they're carving
wheat, they're clearly visiting. If they're not fond of radio, they
could leave information on paper, as a CD, or in whatever form is
convenient. Any such scheme would convey orders of magnitude more
information than a wheat carving.
Surely aliens who can come to
Hampshire are sophisticated enough to offer us more information bits
than one can find on a fortune in a Chinese cookie.
How come they look like us? Hollywood aliens always look pretty
humanoid, but this is an anthropocentric conceit. Visit the local
zoo, and you'll find critters that share 3.5 billion years of
evolution and a lot of your DNA. But they don't look like you - they
look like fish, or alligators, or…
A very important point if you think this is a returned message: The
1974 signal was aimed at the cluster M13, which has hundreds of
thousands of stars. Of course, M13 is 25,000 light-years distant,
which means that the message will not reach its target for another
250 centuries. Clearly, the crop circle can't be a response from any
of M13's inhabitants; they haven't gotten the message yet. But what
about a random, Milky Way star that might be in the "beam" of the
Arecibo message? Couldn't they have overheard the transmission, and
offered this clever carving in reply? No.
The Arecibo beam at 2,380
MHz is about 2 arc-minutes, which is roughly 1/15th the diameter of
the full moon. That's an extremely narrow beam. Imagine shooting an
arrow through a giant space in which ping pong balls are hung by
threads. The ping pong balls are many miles apart. How long would
the arrow have to travel before it accidentally hit one of these
This is analogous to the situation of the Arecibo message,
moving in its tightly focused beam through the spaces of the Milky
Way. The chances that it has hit another solar system in the 27
years since its broadcast are… one in 50,000, approximately. If you
make the reasonable assumption that the aliens cannot travel faster
than the speed of light, then they must lie within 13-1/2
light-years to have received this message and responded.
of a star system within the volume of space filled by the beam out
to this distance is closer to one in a half-million! In other words,
it's highly, highly unlikely that any star system has yet been
exposed to the Arecibo message. This is an important point, as it is
quantitative and not dependent on any other assumptions about this
crop circle: no other star systems could have yet received this
And incidentally, the odds that a nearby probe could
have intercepted it are even smaller!
The biochemistry information in the crop circle is the same as the
Arecibo message, although the DNA seems to have an extra strand and
a somewhat different number of nucleotides. It has also been noted
that silicon is now indicated as part of the biological construction
kit, although this element, while popular in science fiction, is
rather poor at making the complex molecules required for life.
Still, it's remarkable how similar the aliens' biology is to ours,
even to the point of sporting a helical DNA molecule. They also use
the same number of sugars and bases that make up human DNA to
construct theirs. But it's remarkable (but undoubtedly a sign of a
boo-boo on the constructors' part) that the silicon mentioned above
doesn't figure into the formulae of any of these alien DNA
components (this point was made by Randy Wiggins.) In addition, keep
in mind that of the hundreds of possible amino acids, only 20 are
used for earthly life. In other words our biochemistry is somewhat
How curious (and unlikely!) that theirs would match ours
Finally, the whole matter of crop circles fails the baloney test, as
Sagan would put it. They can be easily made by people interested in
creating a stir (you can read a nice description of both crop
circles and their construction, as well as a claim by experts in the
field, as it were, that they could replicate the new grain graphics,
And of importance, there is a lack of convincing
physical evidence that anyone else has made them. You might also
wonder why, despite its ample supply of wheat fields, the U.S. is
almost never the target of this type of alien graphic: nearly
two-thirds of all crop circles are in England. We also note that Chilbolton was the location of other crop circles in 1999 and 2000.
Why would aliens resort to a signaling system that conveys so little
information and can only be used during the two-month growth season,
and then only at night?
We are also informed by Chilbolton that
these recent glyphs appeared (as so many do) after a weekend.
Bottom line? The crop circles are decorative,
provocative, but not informative.
We can expect better from true