There is no single universal 'now' shared across the universe

Rovelli explains that Einstein's relativity destroyed the idea of a single present moment stretching simultaneously across all of space. Whether two distant events happen 'at the same time' depends on the observer's frame of reference and relative motion; there is no privileged, universal clock ticking the same present for everyone everywhere. Two observers moving relative to each other can legitimately disagree about which of two distant events happened first, and neither is wrong—simultaneity itself is not an absolute physical fact but a relationship that depends on the observer. This is not a matter of imperfect measurement; it is a structural feature of how spacetime works. Our everyday sense that 'now' is a shared, universal slice of reality is, Rovelli argues, an approximation that only holds when we ignore the vast distances and relative velocities where relativistic effects become significant, which is why it feels so intuitively obvious despite being physically false at larger scales. Takeaway: 'now' is local, not universal—there is no single present moment for the whole cosmos.