Understanding Tides: A Comprehensive Overview

Introduction

• Tide Phenomenon: Rhythmic changes in ocean levels observed daily.
• Misconceptions: Despite being a common concept, tides are often misunderstood.

Basic Explanation of Tides

• Common Explanation: Moon's gravity pulls ocean water, creating a bulge (high tide).
• Incomplete Logic: Explanation fails to justify the bulge on the opposite side.

Gravitational Forces

• Newton's Law of Universal Gravitation:
  • Gravity produces an attractive force between two objects.
  • Proportional to the product of their masses divided by the square of the distance between them.
• Newton's Second Law (F=MA):
  • Acceleration is proportional to the force applied, divided by the object’s mass.

Tidal Forces Explained

• Two Planets Example:
  • Differing accelerations due to distance, creating deformation (tidal force).
• Circular Particle Model:
  • Circle of particles transforms to an ellipse due to gravitational forces.
  • Tidal Force: Gravitational fields deform celestial bodies.

Tides on Earth

• Earth's Composition:
  • Solid rock with a layer of gas and water.
  • Fluids (atmosphere, oceans) move more easily than solid rock.
• Gravitational Impact:
  • Water on the near side of Earth accelerates faster, forming a bulge.
  • Water on the far side accelerates slower, forming a secondary bulge.
• Earth and Moon Dynamics:
  • Continual acceleration creates tidal bulges.
  • Tidal forces can also deform solid rock over time.

Tidal Forces and Celestial Bodies

• Roche Limit:
  • Defines how close a celestial body can orbit without disintegration due to tidal forces.
• Distance Over Mass:
  • Distance from Earth impacts tidal forces more than the mass of an object.
• Dominant Influence of the Moon:
  • Despite smaller size, proximity makes the moon’s tidal influence significant.

Tidal Constituents

• Lunar Semidiurnal Tide (M2):
  • Completes two cycles in 24 hours and 50 minutes.
• Solar Semidiurnal Tide (S2):
  • Completes two cycles in 24 hours.
• Solar Annual Tide (SA):
  • Period equal to Earth's orbit around the Sun (365.25 days).
• Spring and Neap Tides:
  • Spring Tides: High tides when Moon and Sun align.
  • Neap Tides: Lower high tides when Moon and Sun are at 90-degree angles.

Complexities of Tidal Patterns

• Variability in Tide Magnitudes:
  • Local bathymetry and coastline shape affect tide patterns.
• Bay of Fundy Example:
  • Resonance with M2 tide amplifies tidal range to 50 feet.
• Local Observations:
  • Importance of local knowledge in understanding tide behavior.

Conclusion

• Significance of Tides:
  • Reflect our planet's constant acceleration towards other celestial bodies.
• Observation and Understanding:
  • Engage with local tidal patterns and appreciate the gravitational influences at play.