Carlo Rovelli's views on Time

Forget Everything You Think You Know About Time by Brian Gallagher

Even the notion that the present is fleeting doesn’t hold up to scrutiny. It is certainly true that the present is “horrendously short” in classical, Newtonian physics. “But that’s not the way the world is designed,” Rovelli explained. Light traces a cone, or consecutively larger circles, in four-dimensional spacetime like ripples on a pond that grow larger as they travel. No information can cross the bounds of the light cone because that would require information to travel faster than the speed of light.

“In spacetime, the past is whatever is inside our past light-cone,” Rovelli said, gesturing with his hands the shape of an upside down cone. “So it’s whatever can affect us. The future is this opposite thing,” he went on, now gesturing an upright cone. “So in between the past and the future, there isn’t just a single line—there’s a huge amount of time.” Rovelli asked an audience member to imagine that he lived in Andromeda, which is two and a half million light years away. “A million years of your life would be neither past nor future for me. So the present is not thin; it’s horrendously thick.”

Listening to Rovelli’s description, I was reminded of a phrase from his new book, The Order of Time: Studying time “is like holding a snowflake in your hands: gradually, as you study it, it melts between your fingers and vanishes.”