Brian Greene: Time is Not Absolute – Relativity, Spacetime, and Entropy Explained

The Illusion of Absolute Time

• 💡 Isaac Newton's concept of absolute time, flowing uniformly everywhere, was a widely accepted but ultimately incorrect view of the universe.
• 🔬 The discovery that the speed of light is constant for all observers, regardless of their motion, fundamentally challenged classical physics and the notion of a universal clock.

Einstein's Revolution: Relativity and Spacetime

• 🔑 Albert Einstein's theory of relativity revealed that space and time are not separate but are interwoven into a single entity called spacetime.
• ⚡ Time dilation means time passes differently for observers in relative motion or varying gravitational fields, a point emphasized by Brian Greene.
• ⏳ There is no universal simultaneity; events that are simultaneous for one observer are not for another, implying multiple, observer-dependent timelines.
• 🛰️ Gravity slows time, causing clocks near massive objects to tick slower, a phenomenon crucial for technologies like GPS satellites.

Entropy: The Arrow of Time

• 🎯 While fundamental laws of physics are time-symmetric, entropy explains why time appears to move in only one direction, from past to future.
• 🌱 The universe began in an extraordinarily low-entropy state, and the continuous increase of entropy defines the arrow of time.
• 🧠 Memory is an entropy phenomenon; we remember the past because entropy was lower, and it's impossible to