physical sci: 4th periodical

• they tried to explain the objects in the universe.

• they made observations on the motion of the planets, but were based on mythological knowledge.

scholars of ancient civilizations

• developed an elaborate view of Earth and the universe.

• First to explain the motion of the heavenly bodies using pure systematic observations without incorporating mysticism or myths.

ancient greek scholars

The study of the universe and its components, starting with the theories developed by Greek thinkers and other early astronomers who paved the way for the understanding of planetary motion and cosmological studies.

cosmology

three types of terrestrial motion

1. diurnal motion

2. annual motion

3. precession of the equinoxes

the daily rotation of Earth on its axis from west to east, completing one full spin in approximately 24 hours.

diurnal motion

what are the effects of diurnal motion?

• it causes day and night

• makes celestial objects appear to move across the sky from east to west

• influences wind and ocean currents due to the Coriolis effect

corresponds to Earth's revolution around the Sun, which takes about 365.25 days

Annual motion

It is responsible for the changing seasons and the apparent shift of constellations throughout the year.

annual motion

the slow, conical motion of Earth's axis over a period of approximately 26,000 years

precession of the equinoxes

It gradually shifts the positions of the celestial poles and the timing of equinoxes over long periods.

precession of equinoxes

the most visible stars whose apparent positions are close to the celestial poles.

pole stars

the two imaginary points in the sky where earth’s rotation intersects in the celestial sphere.

celestial poles

occurs when the sun crosses the celestial equator is it moves northward.

vernal equinox

occurs when the sun intersects the celestial sphere as it moves southward along the ecliptic.

autumnal equinox

during his time, the earth was first thought of to be spherical in shape.

Pythagoras

believed to be the perfect geometric shape.

sphere

believed that the most important objects - Earth and the universe according to Plato – are appropriately described as spherical.

greeks

Widely accepted observations that support the notion that Earth is spherical:

1. When ships sail in and out from the harbor, the mast of the ship is the first to appear and last to disappear

2. As you travel north or south, the altitude of the celestial pole changes.

3. During a lunar eclipse, the shadow of the earth is always round, a shadow that only a sphere can produce.

the first to develop models of the universe that are based on natural observations

Ionian school of philosophers (ancient greece)

made use of some ideas from Thales and proposed a cylindrical model of Earth that was stationary at the center of the universe.

anaximander

Earth was surrounded by air, then one or spherical shells with holes in them. The holes appeared as stars because beyond the solid sphere lay a rim of fire.

Anaximander’s model of the universe

placed greater importance on the power and aesthetics of geometry and mathematics over observations and experiments.

pythagoras

a student of Plato and Aristotle, but greatly influenced by Pythagoras

Herakleides

birth of the Geocentric model of the universe

Herakleides

• created a model of the universe in which a spherical earth rotated on its own axis.

• suggested that Mercury and Venus revolved around the sun, while the sun and other planets revolved around Earth.

herakleides

• proposed a model that placed the sun at the center of the universe – the HELIOCENTRIC MODEL – where all planets, including the Earth rotated once a day on its axis and the moon revolved around earth.

Aristarchus of Samos

All matter was made of combinations of four elements

1. earth

2. fire

3. air

4. water

the stars were made of a fifth element that was called

aether

The Earth is stationary and located at the center of the universe.

Geocentric universe

Planets, the Sun, and the Moon move in circular paths around Earth.

circular orbits

small circular motions, equivalent to rotation

epicycle

the epicycle itself moves along a larger circle called the, it is equivalent to revolution

deferent

The stars are embedded in a large celestial sphere that rotates around Earth.

fixed stars

the angle formed between the point C and the location of earth with X as the vertex.

eccentric

The Sun is at the center, and all planets revolve around it.

heliocentric universe

Copernicus still believed that planets moved in perfect circles

circular orbits

Kepler’s three laws of planetary motion

1. The Law of Ellipses

2. The Law of Equal Areas

3. The Law of Harmonies

• Planets do not orbit in perfect circles but in ellipses (oval shapes).

• The Sun is positioned at one focus, not at the center.

• This explains why the distance between the planet and the Sun changes as it orbits.

the law of ellipses

• planets move faster when they are closer to the Sun and slower when they are farther.

• The area covered in a given time is always equal, even though the speed change

the law of equal areas

what is it called when planets move faster when they are closer to the sun?

perihelion

what is it called when planets move slower when they are farther to the sun?

aphelion

• The farther a planet is from the Sun, the longer it takes to complete one orbit.

• The formula: T² = a³

the law of harmonies