“Space and time are no longer a fixed background on which events unfold. They are themselves dynamical entities, which fluctuate and become quantized at the Planck scale.”Carlo Rovelli · Reality Is Not What It Seems: The Journey to Quantum Gravity · 2014 · Reality Is Not What It Seems, Chapter 7: Quantum Gravity, section 'The End of Space and Time'
Space-time is a granular quantum entity, not a passive background.
Rovelli explains loop quantum gravity, where spacetime is made of interwoven quantum loops. At the Planck scale, about 10^-35 meters, space becomes granular, and time disappears as a fundamental variable. For instance, an atom of space cannot be divided further. This means there is no universal time, only relations between events. The theory requires no background, unlike general relativity. Rovelli emphasizes this is a hypothesis, not experimentally confirmed, but it offers a coherent picture of the universe at the quantum scale.
Imagine the universe as a huge canvas. In classical physics, this canvas is smooth and still. Rovelli says that, in fact, the canvas is made of billions of tiny knots that constantly vibrate. Each knot is an atom of space. When you look at something very, very small, you no longer see a continuous surface, but a multitude of discrete points. For example, a phone screen looks smooth, but it is actually made of pixels. Space has a maximum resolution too. This graininess changes everything about how we understand motion and forces.
If space is granular, then time must also be different. Rovelli tells us that at the Planck scale, time simply ceases to exist as a continuous line. It becomes a sequence of events, like the frames of a film. For example, when you play a video game, each frame is a separate moment. There is no time flowing between frames. Likewise, our universe is made of such discrete moments. This means that past and future are not separated by real time, but only by the order of events.
This granularity of space explains why gravity and quantum mechanics did not get along. Rovelli shows that, at the Planck scale, space is no longer smooth but full of fluctuations. For example, when you try to measure a particle's position, the granularity of space makes the measurement uncertain. You can no longer say exactly where something is, only with a probability. This is the origin of quantum uncertainty. It comes from the very structure of space, not from our limitations. This is how the two theories connect.
If space is granular, then causality becomes local. There are no instantaneous actions at a distance, only interactions between neighboring granules. For example, when you kick a ball, the impact travels step by step through the atoms of space, not by a leap. This means every event has a limited neighborhood. Even gravity propagates this way, like a row of dominoes. This explains why the universe seems connected, but without magic. Every change has a well-defined causal chain.
This granularity of space means that even the vacuum is full of energy. At the Planck scale, even apparent emptiness seethes with quantum fluctuations. For example, when you look at a clear sky, you think it is empty. In fact, at the quantum level, pairs of particles are constantly being born and dying there. Rovelli shows that this vacuum energy is a direct consequence of the discrete nature of space. It influences gravity and may explain dark energy. This is how the microcosm connects to the macrocosm.
Why it matters This perspective helps understand why extreme volatility can arise from local interactions without a global cause, similar to quantum fluctuations of spacetime.