I'm not exactly sure, but I think the author is asserting that planets are likely not to be much larger than ours [1] and if that is the case, larger aliens mea

I'm not exactly sure, but I think the author is asserting that planets are likely not to be much larger than ours [1] and if that is the case, larger aliens means they require more space and that puts an upper bound on population size (e.g. the example he gives is if there were as many humans as there were ants, then together all humans would require more energy than what hits earth from the sun). [1] http://thebigalientheory.com/#planets http://thebigalientheory.com/#planets