Physical science

• Spherical Earth

  Arguments for:

  • Positions of the North Star
  • Shape of the Moon and the Sun
  • Disappearance of ships over the horizon
• Calculating the circumference of the Earth

  Eratosthenes' method:

  • Observed the angles of the noonday sun in two Egyptian cities
  • Determined the angle the Sun made with the vertical direction by measuring the shadow of a vertical stick
  • Hypothesized that the light rays from the Sun are parallel and the Earth is curved
• Heliocentrism

  Astronomical model where the Earth and planets revolve around the Sun
• Geocentrism

  Theory where the Earth is assumed to be at the center of the solar system or the universe
• Astronomical phenomena observed before telescopes

  • Rising and setting of the Sun

  Variation in the point where the Sun rises and sets

  Phases of the Moon

  Lunar eclipse

  Solar eclipse

  Daily and annual motion of the stars

  Planets Mercury, Venus, Mars, Jupiter, and Saturn
• Tycho Brahe

  • Danish astronomer who made accurate observations of celestial bodies

  Invented astronomical instruments

  Determined the position of 777 fixed stars
• Johannes Kepler

  • Postulated a force from the Sun that moves the planets

  Concluded that planets move fastest when nearest to the Sun and slowest when farthest
• Kepler's first law

  Each planet moves around the Sun in an elliptical orbit with the Sun at one focus
• Kepler's second law

  The straight line joining a planet and the Sun sweeps out equal areas in space in equal intervals of time
• Kepler's third law

  The square of a planet's orbital period is directly proportional to its average distance from the Sun
• Aristotle's concept of vertical motion

  Vertical motion is natural motion where an object moves and returns to its natural state based on its material or composition
• Aristotle's concept of horizontal motion

  Horizontal motion requires a push or pull force to maintain it, and motion stops when the force is removed
• Aristotle's concept of projectile motion

  Projectile motion is parallel to the ground until the object falls back to the ground, with an impetus keeping the object in motion until it is forgotten
• Galileo's concept of vertical motion

  Objects fall at the same rate regardless of weight, and resistive forces can slow down the fall
• Galileo's concept of horizontal motion

  An object in motion will continue to move if unimpeded, without the need for an external force
• Galileo's concept of projectile motion

  Projectile motion does not require a force to keep it moving
• Inertia

  The tendency of an object to resist change when in motion or at rest
• Newton's first law of motion

  An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force
• Friction

  A force that opposes motion between any surfaces that are touching
• Balanced forces

  Forces where the net force is equal to zero
• Unbalanced forces

  Forces where the net force is greater than zero, causing acceleration