Untitled Quiz

Study Notes

Greek philosophers studied motion, with Aristotle's ideas dominating for centuries. Aristotle, a philosopher and astronomer, reasoned logically from observations.
Celestial realm motion was considered perfect and circular. Objects like stars and planets revolved around Earth in perfect circles.
Terrestrial realm motion was seen as imperfect and unstable. Aristotle believed motion required a cause.
Natural motion was based on the natural tendency of objects to return to their natural state based on their elemental composition. For example, fire moves up, and Earth moves down.
Voluntary motion was unique to humans and animals, driven by internal will.
Involuntary motion occurred in plants and minerals, driven by external forces.

Ancient Greeks observed and reasoned about the Earth's shape, accurately deducing its spherical nature.
Lunar eclipses played a key role, as only a sphere casts a circular shadow.
Eratosthenes measured Earth's circumference using observations of the Sun's position at different latitudes and the assumption that the Sun's rays are parallel. His calculation resulted in a relatively accurate estimate.

Cultures like the Chinese tracked phenomena like comets, meteors, and sunspots.
The Mayans created calendars based on Venus's movements.
Polynesians used stars for navigation over long oceanic distances.
Ancient astronomers recognized diurnal (daily) and annual (yearly) celestial motions.
Diurnal motion is the apparent daily east-to-west movement of celestial bodies due to Earth's rotation.
Annual motion is the yearly shift in star positions caused by Earth's orbit around the Sun.
The zodiac and ecliptic, a band of constellations along the Sun's apparent yearly path, were used to track seasons, predict events, and develop horoscopes, especially by Egyptians.
Equinoxes and solstices (times the sun crosses the celestial equator and is at its furthest declination) were significant points of reference in calendars and agriculture.

Ptolemy proposed a geocentric model, placing Earth at the center of the universe with celestial bodies orbiting it in circular paths.
Epicycles, small circles within larger circles, were used to explain celestial body movements, a feature of Ptolemy's model.
Nicolaus Copernicus developed a heliocentric model, placing the Sun at the center with planets, including Earth, orbiting it in circular paths.
Tycho Brahe proposed a geo-heliocentric model, which combined elements of both Ptolemaic and Copernican ideas.

Galileo improved the telescope, enabling unprecedented observations of the cosmos.
Key Galileo discoveries include: Lunar craters showing an uneven moon, phases of Venus showing it orbiting the Sun, moons of Jupiter, sunspots, and supernovas.
His observations contradicted key elements of the Ptolemaic model, strengthening the Copernican view..

Tycho Brahe meticulously recorded star and planet movements, providing crucial data.
Johannes Kepler used Brahe's data to formulate three laws of planetary motion:
- Planets orbit the Sun in ellipses, not perfect circles.
- Planets sweep out equal areas in equal times, moving faster when closer to the Sun.
- The square of a planet's orbital period is proportional to the cube of its average distance from the Sun.

Vertical Motion: Aristotle believed heavier objects fall faster; Galileo showed all objects fall at the same rate (ignoring air resistance).
Horizontal Motion: Aristotle believed force maintained motion; Galileo introduced inertia (motion continues unless acted upon by an external force).
Projectile Motion: Aristotle thought projectiles travel in straight lines; Galileo showed parabolic trajectories, combining horizontal motion and vertical acceleration due to gravity.

Newton's first law describes inertia (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).
Newton's second law relates force, mass, and acceleration (F = ma). A greater force produces greater acceleration; heavier objects need more force to accelerate.
Newton's third law states that for every action, there's an equal and opposite reaction.

Galileo used inclined planes and experiments to study motion more precisely.
His work directly contradicted Aristotelian physics, and contributed significantly to an understanding of motion.
He also devised thought experiments to envision concepts that were difficult, or impossible, to prove experimentally.