And as we learn more about our place in the universe, what does it all imply for our efforts to find out if there are other living things out there? In the 1600s tradesman and scientist Antony van Leeuwenhoek used his hand-built microscopes to become the first human to see bacteria, a journey that took him into the alien world of the microcosm.Our species has sprung into existence within the barest instant of this universe's enormously long span of history, and it looks like there will be an even longer future that may or may not contain us.The quest to try to find our place, to discover our relevance, can seem like a monumental joke.We must be appallingly silly to imagine we can find any importance for ourselves at all.Yet we are trying to do just that, despite our apparent mediocrity, which became evident when Renaissance scholar Nicolaus Copernicus decentralized Earth from the solar system around 500 years ago.They exist at the edge of feasibility, their bodies endlessly leaking heat that they can barely compensate for by voracious eating.But most mammals are closer to this size than to our size: so much so that the global average body weight of the mammalian population is 40 grams, or less than 1.5 ounces.Put all these factors together, and it is clear that our view of our inner and outer cosmos is highly constrained. Indeed, our basic intuition for random events and our scientific development of statistical inference might have been different under other circumstances of order or disorder, space and time.And the very fact that we are far isolated from any other life in the cosmos—to the extent that we have not spotted or stumbled across it yet—profoundly impacts the conclusions we can draw.Our complex-celled, intelligent bodies are at the boundary of the upper extremes, with comparatively few mammalian types bigger than us. Our sun is not one of the most numerous types of star (most of which are less massive), our orbits are at present more circular and rather more widely spaced apart than most exoplanetary systems, and we do not count a super-Earth among our planetary neighbors.It is an undeniable observation that we exist at this border, this interface between the complex diversity of the biologically small and the limited options of the biologically large. Such a world, a few times more massive than Earth, is represented in at least 60 percent of all systems but not our solar system.