We humans engineer at the chemical level, so when we want to make some new metal alloy using tin, for example, we buy tin that's comprised of the naturally occurring distribution of the 10 stable isotopes of tin that we mine here on the Earth. So this is what we mean when we say that human technology is only using the 80 stable chemical elements - for the most part our technology is much too crude to care about the ratio of isotopes that occur naturally in the ore that we mine for industrial uses - we just exploit the bulk chemical properties of elements, not their isotopes. Obviously fission and fusion technology has been the exception to that rule. Vallee has talked in the past about a sample of material that was found to contain three different isotopes of one element...but those isotopes were perfectly distributed in thirds within that sample. That doesn't happen in nature, ever. So somebody made a material that required an even distribution of all three isotopes of one element, for reasons unknown to us. That indicates a technology which isn't just exploiting the chemical properties of the 80 chemical elements, as we humans do, but rather a technology that engineers with all 252+* stable isotopes of matter. That's what he's saying: somebody has a more nuanced and sophisticated materials science than we do, because we're only now beginning to see uses for isolating and choosing specific isotopes of the elements to achieve industrially useful effects. I hope that clears it up - I don't know how to say it more plainly than that. This is a classic example of confirmation bias. We can only speculate about the nature and function of extraterrestrial technology - you're drawing connections based on extremely tenuous data because you want the data to fit your explanation. You might be right, but you're jumping to all kinds of conclusions here. The color radiated by the materials may have (and probably do have) nothing to do with EM radiation being pumped into metamaterials - it could be an ionization effect, or a thermal effect, or something else entirely. This is why I always argue that arriving at a viable theory of operation is more useful than trying to work backwards in order to make sense of the data. It sounds like you're referring to these two papers: “Electromagnetic stress at the boundary: photon pressure or tension?” Shubo Wang, Jack Ng, Meng Xiao, and C. T. Chan, 2015 https://arxiv.org/ftp/arxiv/papers/1510/1510.06227.pdf “Electromagnetic stress tensor for amorphous metamaterial medium,” Neng Wang, Shubo Wang, Jack Ng, 2018 https://arxiv.org/ftp/arxiv/papers/1801/1801.00942.pdf Those papers show how it's theoretically possible to increase or decrease the mass of a metamaterial by engineering the EM stress-energy tensor equation of the material in a specific way. But the mass of such a material could never drop below zero in this manner because it appears to be impossible to drop the mass of any collection of positive matter below zero and thereby produce negative gravitation (as I understand it, the stress-energy tensor offers no solution where the stress, and momentum, and momentum flux, etc., terms can produce a negative value greater than the T^00 energy density term. Frankly, the more I've thought about it, the more relieved I am that we humans haven't figured out how to emulate AAV field propulsion technology yet. Given the known facts of military history and the current state of geopolitical tensions, I think that if we did know how to achieve gravitational field propulsion then there would be a >90% likelihood of an extinction-level global thermonuclear war within 25 years. So if somebody does figure out how to do it with achievable technology, I would beg them on my knees to stfu about it. * There are estimates of the number of stable isotopes varying from 252 to 256, which probably depend on your definition of "stable."