The edge of science

![Figure][1] To Dartmouth cosmologist Marcelo Gleiser, scientific knowledge is an island in an infinite sea, expanding as we discover, and with an ever-expanding shore of new questions and mysteries. The question he poses in Island of Knowledge is whether or not our failure to know everything is just the technical limitation of the moment, or if there is a point at which something is just plain unknowable. Whatever the answer, he assures us that we should feel neither defeated nor smug; the excitement is in the challenge. The author provides a sweeping didactic and historical introduction to astronomy and physics. It stretches in size from the outer reaches of the universe to the too small to measure and in time from before the Big Bang to the end of eternity. Gleiser has a gift for telling a story grandly and clearly. His history is nothing if not thorough, beginning in early superstition and mythology and methodically working up to current scientific questions in cosmology and physics. Along the way, he touches on everything from philosophy to optics to artificial intelligence. Throughout the book, Gleiser wrestles with the two extremes of the physical world, at times exploring the limitations associated with understanding the vastness of the physical universe and, at others, describing the challenges associated with understanding objects on the quantum scale. I don't fear a “spoiler” here, as the careful cases Gleiser builds in elegant language can't be summarized in this space. But I also warn that the depth of Gleiser's philosophical thought, his analytical approach to history, and his refusal to whitewash technical detail make this a demanding, though stimulating, read. Gleiser paints a clear picture of the way in which our knowledge is dependent on the tools currently at our disposal. He illustrates this idea by describing the limits imposed by the power of the first microscopes and telescopes. Today, he argues, it's the power of our particle accelerators that determines what we can perceive. On the other hand, he maintains that new tools have the power to reveal the breadth of our ignorance, prompting new questions that were previously inconceivable. With the invention of the microscope came the discovery of microscopic life, for example, prompting a slew of new questions about the origins and evolution of life. Of course, science still has some difficulty in grappling with its own provisional nature. It was the religious right that opposed Galileo, but it was clearly the scientific establishment that challenged DNA as the genetic material in the 1940s and later would challenge any idea to the contrary (like Prusiner's prions). It seems the more we endeavor to teach the public about the exquisite process of science, the more we ourselves forget its dependence on confirmation and self-correction. Ambiguity is at the very heart of quantum physics, which Gleiser illustrates with a description of the aptly named Heisenberg uncertainty principle. At least right now, this is a fundamental, physical limit to knowledge. This idea of inherent uncertainty is, perhaps, one of the most humbling limits associated with our quest for understanding. The book is mistitled in that it deals primarily with the limits to the science of physics, rather than science in general, dabbling just a bit in neural science and artificial intelligence. Although the unknown now courses into every branch of science and mathematics, it is arguable whether the true, ultimate bounds of knowledge will indeed be reached in the realm of physics and cosmology. Coming to grips with the ever-changing landscape of fact, and the possibility that some things cannot, by their very nature, be known, is fundamental to our understanding of science and the scientific method. But, as Gleiser argues, this needn't be cause for despair. “To avoid the funk of a modern scientific nihilism, we must find joy in what we are able to learn of the world, even if knowing that we can only be certain of very little.” [1]: pending:yes