Excellent podcast.<br><br>It is true that Silicon is in the same column of the periodic table as Carbon i.e. has a valence of 4 and tetrahedral shape of the atom, but the question is what subvolume of the possible molecule space, whereby molecules have the required threshold complexity (or assembly number), will we find molecules based on Silicon in.  Based on actual things we observe on earth, we know that Carbon-based molecules beat other elements hands down in terms of the formation of long and complex molecules. In other words, for the purposes of getting there quickly is it not better to start with a bag of Carbon as opposed to a bag of sand. It is true that Carbon wins in earthlike conditions. And it is possible that Silicon may produce complex molecules compared to carbon-based molecules, in non-earth-like conditions i.e. temperature, pressure, gravity, viscosity, surface tension, liquid, gaseous state, and other ambient conditions. This chemistry and physics to map out the possible molecules are IMO known. It is true though that to generate the space of possible molecules based on all possible atoms in all possible environmental conditions may require a huge supercomputer to generate/simulate. But in principle, it should be possible. Having said that my bet is on Carbon-based molecules occupying the maximum subvolume of that total volume of space of all possible molecules.<br><br>I think another way to think of Lee's assembly numbers is to think of them as geodesics in the space of all molecules starting from discrete atoms. Ideally, Lee's Chemputer can produce the molecules efficiently by following those geodesics. However, for practical reasons of inability to implement certain hops on the geodesics, the Chemputers may have to follow longer paths than the geodesics. <br><br>Chemistry is for building molecules. And Chemputer is the gadget to implement the building of molecules.  <br><br>Similarly, physics is to build different elements. Alchemy was misled. We need Alphysi. And someone should work on Physisputer as an analog of Lee's Chemputer to build atoms we need. Maybe fusion and fission reactors are those? Then we could build as much lithium and nickel so that we can build as many batteries as our electric vehicles will need in near future. We won't have to be held ransom by evil countries and unethical mining etc.