Not that it’s an essential part of any particular argument, but my understanding was that literal grey goo (independently operating nanomachines breaking down inert matter and converting the whole Earth’s mass in a matter of hours) is probably ruled out by the laws of thermodynamics, because there is no nanoscale way to dissipate heat or generate enough energy to power transformations millions of times faster than biological processes. It also seems like nanomachines would be very vulnerable to heat or radiation because of the square-cube law.
However, less extreme replicators are clearly physically possible because cell division and ribosomes exist. The fact that a literal grey goo scenario is probably ruled out by basic physics does not imply that the ultimate limits for non-biological replicators are close to those for biological replication (which are themselves pretty impressive). Assuming that all small-scale replicators can’t go much faster than Bamboo without a specific reason would be the harmless supernova fallacy. For a scenario that isn’t close to grey goo, but is still much scarier than anything biology can do, see e.g. this.
Not that it’s an essential part of any particular argument, but my understanding was that literal grey goo (independently operating nanomachines breaking down inert matter and converting the whole Earth’s mass in a matter of hours) is probably ruled out by the laws of thermodynamics, because there is no nanoscale way to dissipate heat or generate enough energy to power transformations millions of times faster than biological processes. It also seems like nanomachines would be very vulnerable to heat or radiation because of the square-cube law.
However, less extreme replicators are clearly physically possible because cell division and ribosomes exist. The fact that a literal grey goo scenario is probably ruled out by basic physics does not imply that the ultimate limits for non-biological replicators are close to those for biological replication (which are themselves pretty impressive). Assuming that all small-scale replicators can’t go much faster than Bamboo without a specific reason would be the harmless supernova fallacy. For a scenario that isn’t close to grey goo, but is still much scarier than anything biology can do, see e.g. this.