There Is Something Faster Than

The Conflict: Newton vs. Einstein (Locality) #

• Newton’s Gravity: Established that gravity acts instantly over any distance, a concept Newton himself found absurd but could not explain otherwise.
• Einstein’s Relativity: Proved that nothing travels faster than light. If the sun disappeared, it would take 8 minutes for Earth to react.
• The Problem of Simultaneity: Einstein showed that different observers disagree on the timing of events. If gravity were instant, one observer might see an effect happen before the cause, creating a paradox.
• Locality: Einstein’s theories required "locality," meaning physical influences must spread from point to point at or below the speed of light.

Einstein’s Challenge to Quantum Mechanics (1927) #

• The Wave Function: Quantum mechanics posits that particles exist as a "wave function" of probabilities.
• Instant Collapse: Einstein pointed out that when a particle is detected at one point, its wave function collapses to zero everywhere else instantly.
• Action at a Distance: Einstein argued this implies a "spooky" non-local mechanism that violates the principles of relativity.

The Bohr-Einstein Debates #

• Niels Bohr: Champion of the "Copenhagen Interpretation," which argues that the wave function is merely a tool for prediction and it is meaningless to ask what happens when we aren't looking.
• Bohr’s Victory: History generally records Bohr as the winner of these debates, suggesting Einstein was simply too old and "uncomfortable" with the randomness of the new physics.
• Historian Adam Becker’s View: Becker suggests Bohr often misunderstood Einstein’s actual arguments regarding locality, effectively "winning" by being obscure rather than being correct.

The EPR Paper (1935) #

• Entanglement: Einstein, Podolsky, and Rosen (EPR) proposed a thought experiment involving two entangled particles (e.g., an electron and a positron).
• Conservation of Spin: If one particle is measured as "spin up," the other must be "spin down" to conserve total spin, even if they are light-years apart.
• Hidden Variables: EPR argued that since nothing travels faster than light, the particles must have decided their states locally while they were still together. They called these pre-determined states "hidden variables."

John Bell and Bell’s Theorem (1964) #

• The Breakthrough: John Bell realized that Einstein’s "local hidden variables" theory and the "non-local" Copenhagen theory actually make different statistical predictions if you change the angles of measurement.
• The Disagreement Rate:
  • Quantum Mechanics: Predicts a 25% disagreement rate in specific experimental setups.
  • Local Hidden Variables: Mathematically must result in at least a 33% disagreement rate.
• The Conclusion: Bell proved that no local theory (even with hidden variables) can reproduce the predictions of quantum mechanics.

Experimental Proof: Alain Aspect and Others #

• Testing the Theory: In the 1980s, Alain Aspect performed the first definitive tests using entangled photons.
• The Result: The experiments matched the 25% prediction of quantum mechanics, violating "Bell’s Inequalities."
• Reality of Non-Locality: This proved that the universe is fundamentally non-local; influences do occur faster than the speed of light.

Why No Paradox? (The Speed Limit) #

• No Information Transfer: While the "collapse" is instant, the outcomes are random. Because you cannot control the outcome of your measurement, you cannot use entanglement to send a message faster than light.
• Tame Paradox: This maintains a "truce" with relativity by preventing signals from being sent back in time.

Many Worlds: The Local Alternative? #

• The Many Worlds Interpretation: Proposes that the wave function never collapses; instead, the universe branches into version where every possible outcome happens.
• Restoring Locality: If there is no collapse, there is no need for a "faster than light" signal to tell the other particle what to do. The particles are already in a state of branching.
• Quantum Gravity: Many worlds is gaining popularity because it restores locality, potentially making it easier to unify quantum mechanics with Einstein's general relativity.

Summary #

The video explores the decade-long battle over whether the universe operates "locally." While Einstein believed quantum mechanics was incomplete because it required instant "spooky action at a distance," John Bell’s 1964 theorem allowed scientists to finally test this. Experimental results have since confirmed that the universe is non-local—measurements in one location instantly affect distant particles. While this seems to break light-speed rules, it avoids paradoxes because it cannot be used to transmit information. The "Many Worlds" theory offers a potential loophole where locality is preserved by assuming the universe splits, a radical idea that may eventually help unify all of physics.