Discoveries of Galileo and Newton Module 1

Module One: Discoveries of Galileo and Newton

Galileo Galilei

  • Background

    • From Italy

    • Known as the "Father of experimental science"

    • Improved the telescope for astronomical observations (did not invent)

    • His findings challenged accepted beliefs of his time.

Galileo's Observations

  • The Moon

    • Discovered that the Moon exhibits terrains similar to Earth:

      • Valleys

      • Mountains

      • Craters

  • Sunspots

    • Observed sunspots on the Sun.

    • Sunspots exhibit movement, indicating:

      • The Sun rotates.

      • The Sun is not a perfect sphere.

  • Jupiter's Moons

    • Discovered four largest moons of Jupiter.

    • Previously held belief: A planet would leave moons behind, illustrating lack of understanding of gravity.

  • Phases of Venus

    • Observed phases of Venus, caused by:

      • Orbiting dynamics between the Sun, Venus, and Earth.

      • Changing angles due to different orbital rates.

    • Previous belief: Venus orbited Earth (Ptolemaic system).

Historical Context

  • Conflict with the Church

    • Works of Galileo and Copernicus banned by the Church.

    • Faced restrictions on astronomical work; continued research.

    • Tried by The Inquisition for heresy, forced to retract claims.

    • Lived remainder of his life under house arrest.

Birth of Modern Astronomy

Isaac Newton

  • Galilei, Kepler, and Copernicus lacked explanations for planetary motion.

  • Newton formulated laws of motion and gravity.

    • Mass: Total particles in an object.

    • Weight: Gravitational force acting on an object.

Newton's Laws of Motion

  • First Law

    • Objects remain at rest or in uniform motion unless acted upon by an external force.

  • Inertia

    • Objects resist changes in motion; directly related to mass.

    • More mass means more inertia.

  • Second Law

    • The acceleration of an object is proportional to the net force applied and inversely proportional to its mass:

      • Formula: F = ma (Force = mass x acceleration).

  • Third Law

    • For every action, there is an equal and opposite reaction.

      • Example: A bat hitting a baseball; the bat and ball exert equal forces on each other.

Types of Forces

  • Instantaneous and Continuous Forces

    • Forces that act for a brief moment versus those that persist.

Gravity

  • Nature of Gravity

    • Keeps all objects anchored to Earth and prevents them from flying off.

    • Responsible for planetary orbits.

  • Newton's Universal Law of Gravity

    • Every matter attracts all other matter.

      • Directly proportional to mass; inversely proportional to the square of the distance between them.

Planetary Motion

  • A planet's orbit is the result of:

    • Inertia (Newton’s 1st Law).

    • The gravitational force from the Sun, which deflects the planet towards it.

    • Angular momentum, dependent on speed, mass, and mass distribution.

  • Center of Mass

    • Solar bodies (e.g., Earth and Sun) orbit around a shared center of mass.

  • Kepler’s Law Revised

    • Newton showed planets orbit in elliptical patterns around the Sun, with the center of mass at one focus of the ellipse.

Gravitational Dynamics

  • Two Planets with Same Mass

    • Their orbits are interrelated, sharing a common center of mass.

  • Two Planets with Different Masses

    • The more massive body will have a smaller orbit around a common focus and will move slower.

Conclusions about orbits

  • Sun and planets follow elliptical orbits; the Sun’s orbit around the barycenter is minor compared to that of the planets.

Future Discoveries

  • Newton’s laws led to discovering Neptune.

  • Ongoing exploration for potential ninth planets utilizing Newtonian physics.