Why light speed is actually a limit on cause and effect
In short: If you spin a laser beam fast enough, the dot can move faster than light. This isn't a violation of physics because nothing physical is moving that way. The real speed limit belongs to causality itself: the universe forbids an effect from happening before its cause.
The universal speed limit, denoted as 'c', is not merely a cap on how fast matter can travel; it is the maximum speed at which information or forces can propagate. Because only a force can trigger a change in state, and you cannot transmit information faster than the underlying force field can update, causality is tethered to this constant. Light travels at 'c' specifically because photons are massless, allowing them to reach this maximum velocity without being restricted by mass.
If we were to imagine a universe where light speed was infinite, the fundamental structure of reality would collapse. According to Einstein’s equation E=mc², creating any mass would require an infinite amount of energy. Additionally, Maxwell's equations establish that 'c' represents the reciprocal of the square root for free space permeability and permittivity. If 'c' were infinite, these electromagnetic interactions would cease to occur entirely—meaning no waves could form, and light itself would not exist.
The danger of faster-than-light (FTL) communication lies in the lack of an absolute "now." In special relativity, time is relative to your frame of reference. If Alice on Earth sends an instantaneous signal to Bob traveling at 0.87c toward Proxima Centauri, a paradox emerges. Because their clocks tick at different rates relative to one another, the signal would appear to arrive at Bob's location before it was sent from Alice's perspective. This creates a loop where Alice could receive a reply to a message she hasn't sent yet, allowing for messages to be sent into the past and creating logical contradictions.
Ultimately, the speed of light acts as a cosmic gatekeeper. By ensuring that no signal can bypass the local flow of time, the universe prevents an effect from preceding its cause, thereby maintaining the logical consistency of the timeline.
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Sources
- Summary by Intellect · source: How Faster than Light Speed Breaks CAUSALITY and creates Paradoxes
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