00:00:00 Introduction Rovelli opens by inviting us to question our everyday experience of time. He explains that science has taught us surprising things: time is not what it seems. Time feels steady, but physics reveals cracks in this view. Rovelli uses stories and simple examples to show how time touches every part of our lives, from the ticking of a clock to our memories and plans. He sets out his project: to show that the real nature of time is far different—and stranger—than common sense suggests. He promises to guide the reader through the big discoveries that have changed what we know about time.00:07:24 Part I: The crumbling of time Rovelli describes how the idea of absolute, universal time fell apart in modern physics. Einstein’s relativity: Showed that time is not the same everywhere; it can move faster or slower depending on speed and gravity. There is no absolute “now”; two events can be “now” for one observer, but at different times for another. Time dilation: A clock on an airplane ticks more slowly than one on the ground. Gravity affects the passage of time—clocks closer to Earth’s surface run a bit slower than clocks on a mountain. Quantum mechanics: In the world of atoms and particles, time loses its clear, flowing direction. Fundamental equations describing particles often do not require time at all. Thermodynamics and entropy: The only place where time seems to “move forward” is in the increase of disorder (entropy). This “arrow of time” is why we remember the past, not the future, and why we see cups break but not reassemble. Past, present, future: These are not universal features but may only be reflections of our limited perspective.01:30:09 Part II: The world without time Rovelli pushes us to imagine a universe where time is not a basic ingredient. Timeless equations: The most fundamental equations in quantum gravity (like the Wheeler-DeWitt equation) have no time variable. Physics can describe the universe as a web of events or interactions, not a sequence in time. Relational reality: Objects and events are defined by how they relate to each other, not by a shared timeline. There is no single “universal clock” ticking everywhere. Memory and perception: Our sense of time comes from how our brains connect changes and create stories. “Now” is not a unique moment in the universe, just a perspective from our minds. Block universe: All moments—past, present, and future—exist equally. The feeling of flowing time is an illusion created by how we process information. Human experience: While the universe may be timeless, humans experience time because of memory, anticipation, and change.01:48:51 Part III: The sources of time Rovelli explains how our experience of time can arise from deeper principles. Entropy: The arrow of time comes from the tendency for systems to go from order to disorder. We remember the past because the universe started in a low-entropy (ordered) state. Information and coarse-graining: We do not see every detail of the universe—our minds “coarse-grain” (simplify) what happens. This limited view helps produce the feeling of time passing. Thermal time hypothesis: Time might emerge from the statistical behavior of large numbers of particles. “Thermal time” is a way to describe time that comes from temperature and disorder, not from a fundamental law. Relational time: Events don’t happen “in time”; instead, time is a measure of how things change in relation to each other. Time is built from the web of relationships in the universe.