Albert Einstein and the Theory of Relativity

Introduction

First Postulate: Observers cannot detect uniform motion except relative to other objects.
- Illustrated by train analogy: Uncertainty in motion when observing another train.
- Concludes that there is no absolute rest; everything is relative.
Second Postulate: Speed of light is constant for all observers, regardless of their velocity relative to the source.
- Leads to Einstein's equation: E=mc².
Effects are significant only at velocities near the speed of light; Newtonian physics dominates at lower speeds.

Incorporates both fast motions and acceleration.
Principle of Equivalence: Freely falling in a gravitational field is indistinguishable from uniform acceleration (e.g., a rocket).
Gravity affects objects by influencing space itself.
- Analogy: Trampoline with a bowling ball represents space-time curvature.
- Both masses and light follow curved paths in space-time due to gravity.

Light bends in a gravitational field, observable during solar eclipses.
Differences between Newton's and Einstein's theories:
1. Precession of Mercury's Orbit: Unaccounted portion explained by General Relativity.
2. Gravitational Lensing: Light propagation altered by gravity, confirming Einstein's predictions.
3. Gravitational Redshift: Light from strong gravitational fields shifts to longer wavelengths.

General Theory of Relativity is the current best theory of gravitation.
Differences from Newtonian predictions only under extreme conditions (high velocities, strong gravitational fields).
Newton's laws remain adequate for most everyday and weak gravitational scenarios.