Somewhere in the afterlife, the great-and-gone geniuses of Earth might be gathered around a celestial campfire (or burning bush) roasting heavenly marshmallows, swapping tales of how their creations and theories turned out and having a good laugh at how they continue to baffle humanity long after they’ve left the planet. Two who may be sharing a similar story these days are Enrico Fermi, creator of the Fermi Paradox, and John Von Neumann, proposer of the idea of space probes that can replicate themselves as they travel ad infinitum. A still-living astrophysicist recently pulled these two ideas together and shrunk them down to a microscopic size with his new proposal that aliens may already be among us in the nearly invisible form of self-replicating nanoprobes. Are Fermi and Von Neumann laughing … or crying?
John von Neumann
“In this paper we consider efficiency of self-reproducing extraterrestrial Von-Neumann microscale robots and analyse the observational characteristics. By examining the natural scenario of moving in the HII clouds, it has been found that the timescale of replication might be several years and even less – making the process of observation quite promising. We have shown that by encountering the interstellar protons the probes might be visible at least in the infrared energy band and the corresponding luminosities might reach enormous values.”
In a paper published recently in arxiv, Zaza Osmanov, astrophysicist and professor of physics at the Free University of Tbilisi, Georgia, proposes that Fermi’s Paradox (“where are all of the aliens?”) is due to scientists looking in the wrong place for creatures of the wrong size. He suggests that Von Neumann probes are already here but the machines are a microscopic one nanometer long. (For comparison, a strand of human DNA is 2.5 nanometers in diameter.) At that scale, the probes can be powered by hydrogen atoms – abundant in space – and replicate themselves in just a few years. At that rate, Osmanov estimates a mere 100 nanoprobes launched into space would need only four light years to create – they would create 1,000,000,000,000,000,000,000,000,000,000,000 or 10 to the 33rd power (a decillion) offspring. (Take that, Duggar family!)
While one nanoprobe would be nearly impossible to find, a decillion of them might be easier, especially when feeding on hydrogen atoms. That act would result in emissions that could be luminous, especially to someone looking right at them. At that size and with the right density, Osmanov speculates that the cloud of nanoprobes emitting hydrogen farts could look like a comet. And the place with the highest probability of such a mass gathering would be in interstellar clouds containing a lot of hydrogen atoms. Or perhaps in a zeppelin?
Enrico Fermi
“All the aforementioned results indicate that if one detects a strange object with extremely high values of luminosity increment, that might be a good sign to place the object in the list of extraterrestrial Von-Neumann probe candidates.”
So, if you look at an interstellar cloud and see a luminous object about the size of a comet, it just might be a swarm of alien nanoprobes on their way to Earth. And if you see a smaller luminous blob inside of a hydrogen-filled zeppelin, they may already be here.
Osmanov’s theory is certainly possible and plausible. The real question is … what would Fermi and Von Neumann think?
Are they laughing, crying … or scheming up ways to come back and see what’s next?
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