HOW DO WE KNOW WHAT WE KNOW ABOUT THE COSMOS

There is a grand convergence between ideas and instruments in the field of cosmology at the moment. This has led to a dizzying pace of discoveries that are continually refining our understanding of the cosmos and our place in it. Developments and radical ideas spawned in the past 100 years have laid the foundation for the progress we are currently in the midst of. In my first book, Mapping the Heavens: Radical Scientific Ideas that Reveal the Cosmos, that was published this summer, I take the reader through these developments focusing on the human and psychological side of science. As recently as the early 1900s, our cosmic view was extremely limited – the astronomer Edwin Hubble had just discovered the existence of galaxies other than our own, till then we believed that our galaxy, the Milky Way, stood alone and constituted the entire universe! But since then, there have been dramatic transformations in our view of the universe. Take for example, the discovery that unhinged our view of the heavens as immovable and fixed. Hubble in the 1920’s dislodged the universe and showed that all nearby galaxies were hurtling away from us, indicating that we inhabited an expanding universe. This major disruption revealing that the cosmos was not static led to many more radical refinements in our understanding of the properties of the universe. The aspect that I focus on in the book is the arc of acceptance of several of these key radical ideas, including dark matter, black holes, and dark energy.

As part of our training, we scientists are taught to be open-minded and nimble to accept new ideas as and when new evidence requires rethinking. Despite this, they often resist the new ideas, particularly those that are deeply disorienting and in conflict with entrenched beliefs. The complicated process of acceptance reveals the human side of scientists, their deeply held beliefs, as well their personal ambitions and search for fame. I describe several tussles between individual scientists over the last hundred years, that involve more than intellectual disputes. Interestingly, these disagreements are always finally settled when there is incontrovertible evidence – scientific data in support. As part of the narrative, I also talk about the invention of new technologies – precision instruments, modern telescopes, sophisticated detectors and super-fast computers that have enabled us to make more accurate measurements, gather and organize data to hone our theories.Through stories, I chronicle how we have arrived at our current state of the art understanding, which suggests that we live in a rather peculiar universe where the bulk of the constituents – dark matter and dark energy – remain elusive, and the atoms that we are made of (and that constitute the periodic table of elements) are a mere 4% of the total inventory! Our theoretical understanding suggests that dark matter has played a starring role in structuring the universe by providing the scaffolding that supports the formation of galaxies that we see, while remaining unseen and undetected as yet. While we have measured the effects of the gravity of dark matter on celestial motions and the bending of light, we are yet to detect and find the dark matter particle. So far all our attempts to find it have come up empty. We are actively questing as is the want of science on this cosmic conundrum and many others that I discuss in the book. I offer the readers a glimpse of the status of our current view as well as the many exciting open questions that are driving research in cosmology today.