Wednesday, November 23, 2005

The Crash of the Starship Enterprise: Why humans will not travel to the stars

Part of the American collective identity is related to space exploration. For more than 50 years, elements of our culture have been linked to investigating space with dreams of the eventual movement of humanity to the stars. However, most people who believe this is likely to happen have no idea how empty space is. Looking at the sky on a clear night gives the impression that space is crowded with stars. Creating a scale model of our stellar neighborhood teaches us otherwise.

We can scale a model of the Milky Way by comparing our sun to a grain of sand. The sun is 1.4 million kilometers in diameter. Coarse sand grains range between ½ and 1 millimeter. If we use a 1 mm particle to represent the sun, the model scale is 1 mm = 1,400,000 km. Our nearest star neighbor is Proxima Centauri at a distance of 40.7 trillion km. To scale, the model distance to Proxima Centauri is 28 million mm (28,000 meters). Therefore, if the sun was a 1 mm grain of sand, the next nearest star would be a grain of sand at a distance of more than 17 miles! With the sun at Erwin Building, Proxima Centauri would be in Dansville.

The 400 billion Milky Way stars would be 11 truckloads of sand. This seems like a lot but to scale these would be spread over a circle 67,000 km in diameter—almost five times the diameter of the Earth. That's not even a decent beach. Our stellar neighborhood, fit into a 35-mile radius bubble (the galaxy is not flat) with the Sun at the center, would contain about 30 grains of sand.

Because space is so empty, it takes such a long time to get anywhere. Voyager 1, traveling 17 km per second for over 28 years, has gone less than 11 meters in our model—0.04% of the distance to Proxima Centauri. Glise 876, the closest star to the Earth known to have a planet, would be over 100 km (62 miles) away. Only about two dozen star systems are closer. In 28 years Voyager has traveled 1/9000 of the distance to Glise 876.

Despite this technological challenge, many smart people believe we will explore and/or colonize the stars. Human curiosity, competitiveness and the willingness to climb a mountain “just because it’s there” have driven impressive accomplishments in the past.

Historically, curiosity had only one way to be satisfied—by a person going into the unknown and bringing back knowledge. Curious humans will explore space—just not in person. Space probes based on advances in robotics, computers and nanotechnology, will do our exploring by proxy. While human travel to the stars is not reasonably projected for 300-1000 years, within the next century sophisticated machine explorers will be able to make those trips. Electromechanical explorers will be smaller, smarter, more durable and more expendable than their biological counterparts.

Imagine that a future space probe approaches the planetary system of Glise 876. As it passes by each Glisean planet, it releases subsidiary probes. One instrument is 40-50 nanotech telescope units coordinated into a single viewing system called an interferometer. Over 16,000 times more powerful than any system we have today, it can observe life forms, topography, weather, ocean systems and more in over 200 spectral bands from 100,000 miles above the planet. Miniaturized manufacturing systems land on the planet and produce smart dust using readily available mineral resources. Smart dust units are nano-engineered microscopic sensor/computers that float in the atmosphere and then settle on the surface gathering information and relaying it to a satellite in space. Eventually all these devices self-destruct leaving no trace of their presence. Millions of probe systems send detailed information back to Earth. Possessing overwhelmingly detailed knowledge of every star, planet, dust cloud, nook and cranny in the physical galaxy, to sate our curiosity by sending human bodies out in space ships is redundant at best.

However, humans remain competitive and driven to “climb that mountain.” Whether we retain those characteristics in the coming 3-10 centuries before we are capable of going to the stars remains to be seen. As technology completes the imperative of the Industrial Revolution to free us from hunger, disease, menial labor, and material want will the human soul still aspire to commune among the stars? Or, as Ray Kurzweil asks in The Age of Spiritual Machines: When computers exceed human intelligence will that soul also migrate to mechanical proxies? If so, will they then speed away from Earth, leaving our carbon-based bodies behind?

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