VAULTS IN VACUUM
The central images of the 1968 classic film, 2001: A
Space Odyssey revolve about a mysterious message left in the form of a
monolith buried on our moon. It had been waiting for millions of years for us
to show sufficient ability to uncover it.
Soon after the space program began, scientists proposed sending
messages aboard spacecraft. It's easy see that a long-term message can survive
in the high vacuum and isolation available beyond Earth—deep space equals deep
time. But what should be the medium? And what should be the content of this
message in a bottle?
The first concerted attempt to send a material message
beyond Earth rode upon the first spacecraft to leave our solar system, Pioneers
10 and 11. Launched in 1972 and 1973 to fly by several outer planets, each has
support struts carrying a six-by-nine inch gold-anodized aluminum plaque, which
bears an etched drawing that describes some facts about our civilization. A
sketch of two nude humans, greeting the infinite with a hopeful wave, became
its best-known feature.
In 1977 NASA launched the Voyager missions to the outer
planets, each bearing an Interstellar record created by a team including Carl
Sagan, Frank Drake, and Jon Lomberg. The metal phonograph record carried both
sights and sounds of Earth, from Gregorian chants and seagulls to Chuck Berry,
and set the standard for broadly-based, information-dense messages. Other small
messages—a microdot of inscribed names on the Viking lander to Mars, and an
honorary plaque on the failed Russian Phobos mission to Mars—added nothing new.
More than a decade passed before another substantial
attempt. A CD-ROM disk flew on the Russian Mars '96 mission, which failed at
launch and splashed into the Pacific Ocean.
I worked on the Mars '94 disk, bringing me into close
touch with Jon Lomberg, a major player in the Voyager markers. His paintings
adorn many books and exhibitions; his astronomically-correct rendering of our
galaxy greets visitors to the National Air and Space Museum.
Lomberg had an idea: put a message on the Cassini
spacecraft bound for Saturn in 1997. This and my next two columns deal with
designing such a message.
Lomberg had already enlisted the help of Carolyn Porco, a
professor of astronomy at the University of Arizona, who promised to get such a
message on the spacecraft. Porco was a brisk and efficient woman, a principal
investigator on the Cassini imaging camera team.
Cassini was to be an anthology mission, with eighteen
separate scientific instruments. It also carried a lander which would drop
through the soupy atmosphere of Saturn's largest moon, Titan, and radio back
data from the surface. A duplicate message might also fly aboard the Huygens
Probe lander (named for the discoverer of Titan), built by the European Space
Agency. At 5,562 pounds the Cassini spacecraft would be the heaviest unmanned
package ever launched into the solar system, except for the failed Mars '96
craft. With fuel, it weighed 12,470 pounds and was the last of the dinosaur
generation of spacecraft, having accreted more experiments as the planning
spiraled through many years. Under Daniel Goldin, NASA's approach had reversed
to favoring "lighter, faster, cheaper" missions, and Cassini narrowly
Including staff salaries and assuming it survives for
five operating years in the Saturnian system, Cassini will cost 3.5 billion
dollars. It is surely the last multi-purpose mission to which teams of
scientists glued their hopes and hardware as the mission consumed their
careers. Astronomers exploring the outer solar system must deal with long
flight times, but the repeated delays of Cassini meant that some of them would
have only this single opportunity. After Cassini, missions will be quick,
light, cheap—and politically stronger. NASA's extreme sensitivity to Congress
grew from years of narrowly getting Cassini past their skeptical eyes. The
agency became risk-averse as launch dates approached, a fact that came to have
great significance as the drama of the Cassini marker unfolded.
While we were working on the Cassini marker, the Mars '96
mission ended up in the Pacific Ocean. It failed to reach orbit because the Russian
Proton booster misfired in its fourth rocket stage. Again, the craft was so
heavy that a fourth stage was essential. Many experiments were lost, the Visions
of Mars disk with them. There was some consolation that the disk may fly on a
later Russian Mars mission.
Cassini is an implausibly fat spacecraft, so heavy that
it has to undergo two gravity-assist flybys of Venus, and one each of Earth and
Jupiter. Arriving at Saturn late in 2004, it will fire an onboard rocket to brake
it into the first of some six-dozen orbits during its planned four-year tour.
Shortly after arrival, the Huygens lander will separate and plunge into the
chilly, hazy-brown atmosphere of Titan.
Apparently Titan has at least one continent, perhaps
jutting up from chilly seas of liquid hydrocarbons like ethane. Organically
rich, its atmosphere is thicker at the surface than Earth's, but at
temperatures around -170 centigrade. No one has any good idea of what such
frigid chemistry could produce, over the four billion years Titan has orbited
November of 1994, Lomberg and I wrote to the Jet Propulsion Laboratory (JPL),
who were assembling the spacecraft. As with Mars '94, we suggested attaching an
existing small package, the Microelectronics and Photonics Exposure experiment
(MAPEX), plus a message. Lomberg thought adding MAPEX might make the marker
more saleable. We tried to hawk the idea with the usual positives:
public awareness of the mission, as the Pioneer plaque did, through an
optimistic, imaginative goal.
a broad public about the lander, Titan's strange chemistry, and the problems of
communicating across long timescales.
The eventual audience could be humanity centuries hence,
or on a far longer time scale, any life-forms that evolve in the organic soup
of Titan. We would not imply that Titan bears life now, but would allow for
later evolution. We sketched out the plausible readers, ranging from our
distant heirs (1,000 to 100,000 years) to aliens, including possible Titanians,
on scales of a million to billions of years.
Porco came to the University of California at Irvine and
we three spent days brainstorming design ideas over lunches and dinners. Much
scientific work proceeds like this, sighting in on the critical problems, then
using the skills of each team member to attack them. Such free-for-alls are one
of the best aspects of scientific collaboration, spirited and enjoyable. They
are quite the opposite of how other creative people work, as in the classic
image of solitary, agonized artists.
Labor and material costs were to be kept low. We thought
the message-bearer should probably be an "artificial fossil" embedded
in hard glass which could survive Titan's weather. The message would thus
outlast the lander by far.
Unlike the wandering Voyager strategy, we could shape our
message for a specific place, Saturn and Titan. We could include information
about the present solar system (which cannot be seen in visible light through
Titan's thick atmosphere) and our place in it. Communicating this in clear,
unambiguous ways promised to be an imaginative intellectual exercise, raising
interwoven cultural and scientific issues of wide interest. We would aim to be
"understandable, optimistic and awe-inspiring."
JPL said they would submit the idea through the usual
channels; Carolyn Porco promised to hurry it along.
Mulling over the huge time scales a week later, I
realized that Titan's frigid weathering and the lacerating forces the orbiter
would meet around Saturn suggested a message medium of great durability.
Engineers estimated the orbiter would remain intact in
orbit for roughly a century, while the Huygens lander could be buried by the
flows of sluggish, cold fluids within decades. These were very crude
projections, given Titan's unknown weather. In both environments, diamond would
preserve a message against abrasion better than metals.
To me the best candidate appeared to be a thin,
single-crystal diamond disk to write upon. Using a jewel to carry a message
across a billion years could delight the mind as well.
Manufacturing a disk bigger than a nickel would be
expensive. And how to write on the hardest of all substances? At first I
thought of using writing processes I knew, such as a layer of boron inside the
sheet, laid down using a template and chemical vapor deposition.
The utility of this approach lay in its simplicity,
readability, and the unequalled rugged properties of single diamond crystals.
Diamond is robust, strong, inert, and resists abrasion. Only very high
temperatures and aggressive oxides can damage it. Further, it is transparent in
the visible spectrum and a broad range of the infrared. Many spacecraft use
diamond windows for their infrared sensors and its space-rated properties are
well known. On Titan, infrared is probably the preferred range for best
visibility. Diamond has no known chemical reaction with substances in the Titan
Construction of the marker would begin with purchase of
an industrial diamond plate, polished, about one millimeter thick. My
discussions with the leading diamond firm, De Beers, proved this was not a
routine request, but they could make such diamond disks for about $5,000 each.
Since cost scales quickly with size, maximum diameter would be at most a few
Writing a microscopic message into the planes of a
diamond would probably be attractive to the general audience, I thought, much
as the gold-plated Voyager disk proved eye-catching. Indeed, DeBeers seemed
interested in the jewelry angle as a possible new market: wear the Cassini
Medallion! At perhaps $30,000 or more, this would be a very high-end item.
Lomberg, Porco, and I visited JPL and spoke with the
flight engineers and managers, with Porco fielding this proposal in Europe. The
jewel message notion seemed to catch the attention of even skeptical engineers.
We had approval within a month. The European Space Agency also liked the idea
and agreed to carry a diamond disk on the Huygens lander.
Word came to me late in the evening, by telephone from a
jubilant Lomberg. I walked outside and viewed the stars, thinking of the marker
as a sort of memorial for all the scientific community, and indeed, for our
era. The sheer joy of it made it difficult for me to speak. I remembered that
awe is a blending of wonder and fear, and realized whence my fear came. The
time scales of astronomy imply the mortality of those who study it. No less
does designing a message which could not be read until all its designers are
dust. The night sky filled me with a chilly awe in a way it never had before.
I went back inside and set to work. Soon enough,
consultation with DeBeers converged upon a disk 2.8 centimeters across, a
millimeter thick and weighing 4.3 grams. Each spacecraft would carry the same
message. Though we had two years until the diamond disk had to be attached to
the spacecraft and lander, there were myriad engineering and conceptual issues
* * *
We wished to build on the Voyager experience, extending
their thinking. As with Voyager, NASA reserved the right to veto us or even
drop the marker entirely. When Voyager design ideas leaked to the press in
1977, NASA's official posture was that they had made no final decision on the
project at all.
Still, this did not protect from public vitriol the
makeshift team making the Voyager record. Shadowy rumors emerged at the United
Nations, when they tried to get diplomats to record verbal greetings to go on
the record. Some felt Voyager should carry depictions of war, poverty, and
disease, and that a best-foot-forward approach was a sunny half-truth.
Early on the designers had decided to avoid explicit
depiction of religion, lest they ignore some. Afterward, others questioned
whether the team's belief in the scientific method and use of it to convey much
of the message was not itself a sort of ideology. Editorials in the British
press had demanded that any future messages be crafted by a large international
ecumenical assortment of scientists and non-specialists alike.
We three had no liking for such an unwieldy opera of
interests. NASA agreed; we would design and deliver a disk, following solely
our own judgment and paying the cost ourselves.
Before beginning, we had to assume that our future
readers could indeed read. Brains often must decipher the visual world from ambiguous,
ill-defined data. Like many other animals, we make educated guesses about what
lies behind our sometimes chaotic environment. Evolution has shaped our brains
to create models of the world that mesh well with our learned reality.
At least a third of our approximately hundred thousand
genes are exclusively involved in brain function, and many of those relate to
sight. We use a strategy of storing a perception across many neurons, much as
TV sets break images into pixels.
This method is like the great Rose Bowl prank of 1961,
when Caltech students stole the coding sheets for the University of
Washington's mass card display. The students then doctored these and returned
them to the hotel safe where they were stored. No Washington fan knew the
message beforehand, so none could tell that anything was wrong. Each Washington
fan knew only to hold up his white or black card, following written orders
handed out at the game. When the stadium crowd held aloft their cards, they
spelled CALTECH. The next image in this little half-time entertainment was of
the Caltech Beaver, not the Washington Huskies.
Like the fans, our neurons know nothing. But parallel
processing of their individual minute signals, carried up through hierarchies
of neural organization, eventually constructs a model of what the eye is
seeing. The brain uses this image in making evolutionarily effective
calculations and decisions.
For example, if we paint dots on a hollow glass cylinder
and view it with one eye, it looks like a random set of two-dimensional dots.
But turn it and—aha!—the three dimensional shape of the glass pops out, a whole
three-dimensional picture. Our brain generates this from a mere bit of motion,
a talent of great use in the African veld long ago. Similarly, stereo vision
enables our brains to take the small differences in the angles that objects
make and decode them into distance estimates.
All this processing plays out behind the sets of our
internal, unitary world. We had to assume our future audience would have such abilities
as well, but perhaps not exactly ours.
Voyager's messages had embodied the idea that the
aesthetic properties of human art (especially music, since they were sending a
record) emerged from physical constants and nature's mathematical harmonies. Intelligences
of the far future, springing from physical circumstances at least partially
shared with us, might well appreciate underlying ideas based on natural order.
Lomberg speculated that highly ordered structures like fugues and geometric
constructions might come through best.
Conventions of perspective and the entire problem of
interpreting two-dimensional representations loomed large. Even those humans
whose cultures do not use perspective have to learn how to see it. Dogs never
do learn. What of humans evolved in a far future? Or even aliens?
It had always seemed to me that evolutionary mechanisms
should select for living forms that respond to nature's underlying
simplicities. Of course, it is difficult to know in general just what simple
patterns the universe has. In a sense they may be like Plato's perfect forms,
the geometric constructions such as the circle and polygons, which supposedly
we see in their abstract perfection with our mind's eye, but in the actual
world are only approximately realized. Thinking further in like fashion, we can
sense simple, elegant ways to viewing dynamical systems, calling forth ideas of
the irreducibly elementary.
Imagine a primate ancestor for whom the flight of a
stone, thrown after fleeing prey, was a complicated matter, hard to predict. It
could try a hunting strategy using stones or even spears, but with limited
success, because complicated curves are hard to understand. A cousin who saw in
the stone's flight a simple and graceful parabola would have a better chance of
predicting where it would fall. The cousin would eat more often and presumably
reproduce more as well. Neural wiring could reinforce this behavior by
instilling a sense of genuine pleasure at the sight of an artful parabola.
We descend from that appreciative cousin. Baseball
outfielders learn to sense a ball's deviations from its parabolic descent, due
to air friction and wind, because they are building on mental processing
machinery finely tuned to the problem. Other appreciations of natural geometric
ordering could emerge from hunting maneuvers on flat plains, from the clever
design of simple tools, and the like. We all share an appreciation for the
beauty of simplicity, a sense emerging from our origins.
In an academic paper, René Lemarchand and Jon Lomberg had
argued in detail that symmetries and other aesthetic principles should be truly
universal, because they arise from
Many things in nature, inanimate and living, show
bilateral, radial, concentric and other mathematically based symmetries. Our
rectangular houses, football fields and books spring from engineering
constraints, their beauty arising from necessity. We appreciate the curve of a
suspension bridge, intuitively sensing the urgencies of gravity and tension.
Radial symmetry appears in the mandala patterns of almost
every human culture, from Gothic stoneworks to Chinese rugs. Perhaps they echo
the sun's glare flattened into two dimensions. In all cultures, small flaws in
strict symmetries express artful creativity. As Lemarchand and Lomberg note,
the universe itself began with a Big Bang that can be envisioned as a
four-dimensional symmetric expansion; yet "without some flaws, so-called
anisotropies, in the symmetry of the Big Bang, galaxies and stars would never
A less obvious mathematical underpinning expresses itself
in forms as diverse as the chambered nautilus, flower petals and galaxies. Draw
three diagonals in a pentagon, and the intersections divide the lines in a
ratio, 1/2(1+51/2) = 1.61803... The ancient Greeks noticed that this
"Golden Section" in geometry emerged in many strikingly different
ways. The human eye finds its echo pleasing in our own buildings; the Greeks
When its pediment was intact, the Parthenon fit exactly
into a rectangle with this ratio of sides. This proportion was first discovered
by the Greek mathematician Pythagoras 2,500 years ago; the sculptor Phidias
used it. The United Nations building in New York City is proportioned as three
Natural philosophers noticed that this number also
appears in a famous sequence, the Fibonacci series (0, 1, 1, 2, 3, 5, 8, 13,
21...), which nature favors as well. Arrived at simply by summing the previous
two entries in the sequence, this pattern appears in the branching pattern of
trees, in the number of petals in the iris, primrose, and daisy, and in many
other flowers. Pinecones, pineapples and sunflowers display overlapping
clockwise and counter-fundamental physical properties. Aliens orbiting distant
stars will still spring from evolutionary forces that reward a deep, automatic
understanding of the laws of mechanics. clockwise patterns, their florets in
the ratio of successive Fibonacci numbers, such as 21:34 in the sunflower. The
Golden Section emerges when one takes the ratio of two successive terms; the
higher these terms are, the nearer their ratio to 1.61803...
The Golden Section emerges from spirals by drawing
perpendicular lines connecting different parts of the curve. The ratio of the
lengths of adjacent lines is a close approximation to 1.6180... The spiral of
the chambered nautilus follows the Golden Section, as do the curves of
seashells and animal horns. Apparently the necessities of strong structures
built from minimal materials force such underlying choices to emerge from the
pressures of evolution. Growing in a fixed proportion does not shift the center
of gravity, so balance problems do not develop.
Quite different physics generates the spiral waves in
galaxies, yet in many these curves too express the Golden Section, sometimes
also called the logarithmic spiral. The Golden Section lives in flowers, trees
and galaxies, giving pattern to our entire universe, yet known only to a few of
To those who have not had their sense of mathematics
squashed by the mechanical drills of elementary school, the subject can burn
with a peculiar rich intensity. Would aliens (or even further evolved humans)
"see" the same mathematical underpinnings to our universe?
Strategies for the Search for Extraterrestrial
Intelligence, SETI, have assumed this since their beginnings in the early 1960s.
Many supposed that interesting properties such as the prime numbers, which do
not appear in nature, would figure in schemes to send messages by radio. A case
for the universality of mathematics is in turn an argument for the universality
of aesthetic principles: evolution would shape all of us to the general
contours of physical reality. The specifics could differ enormously, of course,
as a glance at the odd creatures in our fossil record shows.
Our prospect was daunting. Many mathematical paths
beckoned. For example, was there a way to embed in our message the compact
equation eipi+1=0 which links the most important constants in the
whole of mathematical analysis, O, 1, e, pi and i? The equation looked
beautiful to me, a "math type" as my wife dryly noted, but such types
comprise a tiny audience even among humans.
What's more, we could not even find a clear way
(independent of many assumptions about notation) to write the equation. Any
writing scheme called upon human symbols. Such points stumped us. After all,
philosophers of mathematics have argued over whether a mathematical object,
like "9", is independent of human thought, or not. Some hold that it
is neither external nor internal but social. This means mathematical ideas
arise from our interactions with each other. Then a theorem known solely to its
inventor does not in some sense even exist as mathematics until someone else
understands it. Plates are round, an objective fact, but mathematical roundness
is a human construction.
Perhaps. But all three views—mathematics is objective and
real; it arises from an internal set of preconceptions; it is social—ignore
biology, which brought about humans themselves through evolution. How general
were our adaptations to our world?
How to decide such fundamental points? Our imaginations
yearned to soar but momentarily stalled. In the end, we retreated to our sense
Further difficulties arose in areas I had naively thought
were straightforward. How to depict our solar system? To use mathematical
universals, even once identified? How about the data processing assumptions
behind recovering three-dimensionality through two-dimensional projections? How
universal could be the use of scientific diagrams, our design of mathematical
symbols, and the use of photos of humans?
All involved standing at a conceptual distance from
ourselves, reaching for a more general way of seeing the world. But how firmly
could we believe arguments from our own sense of beauty?