Science & Technology

Could We Use Self-Replicating Machines to Explore the Universe?

We might dream of traveling to distant galaxies one day, but right now, Earth technology can barely get an uncrewed spacecraft beyond our solar system. Outer space is really, really big, and even at near light speed, it would take years to reach our closest neighboring star and many more to reach galaxies beyond our own. By that time, even an uncrewed probe would be a decrepit hunk of metal programmed with obsolete technology. That is, unless we programmed the probe to make more of itself. Some have said self-replicating probes are the future of space travel — but others say their potential suggests bad news about intelligent life beyond Earth.

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A self-replicating robot is often referred to as a Von Neumann machine after the Hungarian-born American mathematician John von Neumann. He was the first to mathematically model a machine that could replicate itself. In today's world of 3D printers, that might sound like a simple task, but this was the 1940s. Von Neumann conceived of this "universal constructor," as he called it, at a point when computers barely existed. Still, as ambitious as it was, he never conceived of using it for spacecraft.

That idea came decades later in a 1979 book by Chris Boyce, though he credited the work that others had done years before. Here's how he envisioned it: You'd launch a Von Neumann probe (that is, a spacecraft that can replicate itself) equipped with an interstellar propulsion system and send it to a neighboring star system. Once it got there, it could mine asteroids and planets to gather the raw materials it would need to replicate itself. It would make several copies of itself, which would themselves launch toward neighboring star systems. Each of those Von Neumann probes would repeat the process, and before you knew it (that is, after a few million years), you'd have probes exploring every corner of the galaxy.

But these probes wouldn't just make more of themselves — they'd also do important scientific research and transmit their findings back to their homeworld. You could even conceive of a probe designed to colonize the galaxy with life if the technology was advanced enough to terraform planets and synthesize human embryos.

It's such a good idea that it's made a few thinkers come to some depressing conclusions. In a 1981 paper bluntly titled "Extraterrestrial Beings Do Not Exist," cosmologist Frank Tipler pointed to the fact that if advanced civilizations are out there, self-replicating probes should be everywhere — including our own backyard. "If [extraterrestrial intelligent beings] did exist and possessed the technology for interstellar communication, they would also have developed interstellar travel and thus would already be present in our solar system," he wrote. "Since they are not here, it follows that they do not exist."

Back in the Real World

But forget extraterrestrials — how close are we to making Von Neumann probes? Well, NASA has definitely thought about it. In the 1980s, they sponsored a study investigating the possibilities of advanced automation for space missions. One such possibility was a potential 20-year program to install a self-replicating lunar manufacturing facility on the moon. According to this plan, they'd have to build the first machine themselves, but after that, it would only require raw materials it could mine from the lunar surface. Unfortunately, the plan never materialized.

But scientists are still exploring the possibilities. In 2017, for example, Canadian scientists announced that they had been developing 3D printers that could replicate themselves from lunar material, and researchers at North Dakota State University have been working on something similar. There's still a long way to go, but this is one technology that doesn't seem so far-fetched.

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Love thinking about what the future might hold? Then you've got to check out "The Future of Humanity: Terraforming Mars, Interstellar Travel, Immortality, and Our Destiny Beyond Earth" by Michio Kaku. The audiobook is free with an Audible trial. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer May 31, 2019

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