The All World Gayatri Pariwar is a modern religious movement that enjoys wide popularity in North India, particularly among the many STEM workers who joined after becoming disillusioned with their lucrative but unfulfilling private-sector careers. Founded in the mid-twentieth century, the Gayatri Pariwar works to popularize practices inspired by ancient religious texts and breaks with convention by framing these practices as the foundation of a universal spirituality. The movement appeals to science in its advocacy of these practices, claiming that they have medical benefits that constitute proof that rational people around the world should find persuasive. Should these practices become sufficiently widespread, the belief is that humanity will enter a new satyug, or "golden age." In The Science of Satyug, Daniel Heifetz focuses on how religion and science are objects of intense emotion that help to constitute identities. Weaving engaging ethnographic anecdotes together with readings of Gayatri Pariwar literature, Heifetz interprets this material in light of classic and contemporary theory. The result is a significant contribution to current conversations about the globalized middle classes and the entanglement of religion and science that will appeal to anyone interested in understanding these aspects of life in modern India.