The speed of light is the upper limit for information transfer in the universe due to the structure of space and time as described by Einstein’s theory of special relativity. Here’s why:
- Causality preservation: If information could travel faster than light, it would be possible for an effect to occur before its cause in some reference frames. This would violate causality—one of the fundamental principles of physics.
- Relativity of simultaneity: Special relativity shows that simultaneity is relative; two observers moving at different speeds can disagree on the order of events. Faster-than-light signals would lead to contradictions in the sequence of events, making cause and effect ambiguous.
- Infinite energy requirement: As an object approaches the speed of light, its relativistic mass increases. To accelerate any particle with mass to the speed of light would require infinite energy, which is physically impossible. Only massless particles, like photons, can travel at light speed.
- Light cone structure: The light cone defines the limit of causal influence. Any event outside an observer’s future light cone is unreachable by any signal or information because it would require faster-than-light travel.
- Consistency of physical laws: The constancy of the speed of light in all inertial frames ensures that the laws of physics remain the same everywhere. Allowing faster-than-light transfer would break this consistency.
Thus, the speed of light isn’t just a speed—it’s the fundamental boundary that keeps space, time, and cause-and-effect coherent across the universe.