destined to go to the stars. That's the assumption we've been making for a
century, and I daresay most readers believe this as surely as they believe
we'll eventually cure dandruff.
of an interstellar destiny is not merely the consequence of too many
couch-hours spent watching Spandex-suitedastronauts in Star
Trek, Star Wars, or Futurama. It's been a subtext of our
space program. You might recall a low-grade, 1960 biopic about Wernher von Braun
entitled I Aim at the Stars. Or perhaps you know the sunny motto of the
National Space Society: "ad astra" ("to the stars"). Boldly sending our descendants
into the galaxy's stellar realms seems as inevitable as teen sex.
I like the
idea of becoming
a spacefaring society. It's just a matter of how far we'll fare. Yes, we'll
colonize our cosmic backyard; after all, if our species has not spread beyond
Earth within a century, then we're headed for eternal internal conflict and armageddon@home.
In the words of rocket pioneer Konstantin Tsiolkovsky, humans can't stay in the
we'll soon be landing people on Mars, and eventually the satellites of the
outer planets. I anticipate the construction of space habitats on the moon, the
asteroids, and in orbit around Earth.
the vicinities of other stars is enormously harder than settling the solar
system. Our fastest rockets can take us to Neptune in less than a decade - a
long ride, but not inconceivable. On the other hand, a trip
to the closest star system, Alpha Centauri, would take 75,000 years.
lifetimes are typically a century or less, practical travel to the stars
requires relativistic velocities. Sending a 100-ton habitat, stuffed with a
small crew, to Alpha Centauri at a speed that will deliver them before they turn
up their toes requires as much energy as the United States consumes in a year. At
standard utility rates, that will cost you about $3 trillion, just for the fuel.
Now this is
a familiar discourse, and the usual rejoinder is to appeal to the inevitable
development of faster rockets. We'll still go to the stars; we just need better
me to point out something both relevant and important: our remote sensing
technology is improving much faster than our rocket technology. And that is a
at some numbers. Von Braun's V-2 rockets crossed the English Channel at 1 mile
per second. NASA's New Horizons mission to Pluto - the fastest
spacecraft ever launched - is headed to this erstwhile planet at 10 miles
per second. That's an order-of-magnitude improvement after 70 years.
consider one component of our remote sensing capabilities - our ability to
"see" what we're exploring. The Mariner 4 spacecraft - the first to snap decent
photos of Mars - was fitted with a monochrome TV camera having a resolution of
40 thousand pixels. In the summer of 1965, it sailed by the red planet while
imaging craters as small as a few miles across.
HiRISE camera on NASA's
Mars Reconnaissance Orbiter boasts a resolution of 200 million pixels (and shoots
in color). It can discern items on the surface as small as a horse.
words, in seven decades our rockets sped up by a factor of ten, but in little
more than half that time our cameras improved by a factor of five thousand.
There's no comparison: probe technology is marching to the beat of a faster
always offered the advantage of lower cost and minimal risk. For interstellar
travel, their smaller size makes them especially practical. For the same energy
bill, you could propel a one-ton reconnaissance craft to another star in
one-tenth the time of sending even a small clutch of humans.
might argue that human exploration is qualitatively different than sending mechanical
proxies. We humans want to experience the frontier, not just watch it
come up on our computer screen. We want to smell it, feel it, and look around.
what if we could send back all those sensations with a fidelity as good as
being there? That's becoming more and more practical. The bandwidth of a
single human eye, recently measured at the University of Pennsylvania medical
school, is roughly 2 megabytes per second. The bandwidth of your ears is much
smaller - no more than a few hundred kilobytes per second. Your fingertips and
other parts of your anatomy require even less of a data pipe.
words, we could send back everything a human could sense with a
telemetry channel of, say, 10 megabytes per second. This is roughly the data
rate you'll soon be getting off a blue-ray disk. It's not trivial to send data
at this rate from star to star, but it's a lot easier than sending ourselves.
technology that can propel us virtually into deep space is quickly
outstripping the technology that can propel our protoplasm there. So while we
envision our 23rd century descendants cruising the Milky Way in
search of other beings or fresh real estate, my guess is that we'll send small
robots instead - extensions to our neurons that can be both cheap and
our descendants among the nearby worlds of our solar system is more than our
destiny: it's an imperative for our future. But galactic exploration will be
different: that's something we'll do from the comfort of our own homes. And we
won't need the Spandex.