The Story of Tides: From Alexander to Newton

Ancient Tales and Modern Science

• 326 BCE: Alexander's Army

  • Army exhausted and retreated due to fruitless fighting and monsoon rains in India.
  • Experienced a tidal bore on the Indus River, surprising them with a massive wave.

• Tidal Bores

  • Created by high tides pushing seawater up rivers.
  • Contrast with mild tides of the Mediterranean.

Understanding Tides

• Isaac Newton's Contribution

  • 2,000 years after Alexander, Newton explained tides via the laws of gravity.
  • Tides are influenced by celestial object motions, primarily driven by the Moon.

• Gravitational Dynamics

  • Moon's gravity causes tidal bulges on Earth.
  • Earth and Moon orbit around a shared center of mass.
  • Earth rotates, leading to two daily high and low tides.

• Sun's Influence

  • Sun also affects tides, creating variations with Moon phases.
  • Spring Tides: Extreme high tides during a full Moon.
  • Neap Tides: Minimum low tides when Moon is half-full.

Complexity and Variability

• Landscape Impact

  • Tide strength varies based on local geography; bays and inlets have strongest tides.

• Other Celestial Bodies

  • Moons like Europa and Enceladus experience dramatic tidal forces due to Jupiter and Saturn.
  • Io experiences strong tidal forces, resulting in volcanic activity.
  • Extreme tidal forces can lock planets in place around stars.

Tidal Locking and Earth's Future

• Tidal Locking Phenomenon

  • Over 50 billion years, Earth could become tidally locked to the Moon due to oceanic friction slowing rotation.

• Solar System Endgame

  • This scenario is unlikely as the Sun will have died first, taking Earth with it.

This document provides a historical perspective on tides, beginning with ancient observations and leading into Newton's scientific explanation, exploring the complexity of tide mechanics and their cosmic significance.