Untitled Flashcard Set

Why Ancient Humans Studied the Sky

Importance of the Sky

Ancient civilizations depended on observations of celestial bodies for:

• Religion and rituals

• Celebrations and festivals

• Agriculture

• Timekeeping

• Navigation

• Architecture

• Calendar creation

Seasonal Tracking

• Constellations and stars were used to identify seasons.

• Farmers used celestial observations to know when to plant and harvest crops.

Ancient Civilizations and Astronomy

Many civilizations made important astronomical observations:

• Mesopotamia

• Ancient Egypt

• China

• India

• Polynesia

• Ancient Greece

• Europe

Contributions

• Developed calendars.

• Aligned buildings with celestial objects.

• Navigated oceans using stars.

• Recorded planetary and stellar movements.

Constellations

Definition

A constellation is a group of stars that appears to form a pattern when viewed from Earth.

Famous Constellations

• Ursa Major (Great Bear)

• Ursa Minor (Little Bear)

• Cassiopeia

• Draco

• Orion

Uses of Constellations

• Navigation

• Timekeeping

• Seasonal indicators

• Cultural and mythological stories

Development of Models of the Universe

Geocentric Model

Aristotle

Aristotle

• Proposed the geocentric model.

• Earth is at the center of the universe.

• Sun, Moon, planets, and stars revolve around Earth.

Heliocentric Model

Aristarchus of Samos

Aristarchus of Samos

• Proposed the heliocentric model.

• Sun is at the center.

• Earth and planets orbit the Sun.

Major Astronomers

Ptolemy

Claudius Ptolemy

• Refined the geocentric model.

Copernicus

Nicolaus Copernicus

• Revived the heliocentric model.

Galileo

Galileo Galilei

• Used telescopes to gather evidence supporting heliocentrism.

Tycho Brahe

Tycho Brahe

• Made highly accurate observations of planetary positions.

Kepler

Johannes Kepler

• Developed the three laws of planetary motion.

• Showed that planetary orbits are elliptical.

Newton

Isaac Newton

• Explained planetary motion using gravity.

• Developed laws of motion and universal gravitation.

Accepted Solar System Model

Modern View

• The Solar System is heliocentric.

• Planets orbit the Sun.

• Orbits are elliptical rather than perfectly circular.

Modern Contributions

Albert Einstein

Albert Einstein

Theory of Relativity

• Improved understanding of gravity, space, and time.

• Showed that gravity results from the curvature of spacetime.

Henrietta Swan Leavitt

Henrietta Swan Leavitt

Major Contribution

• Developed a method for measuring vast cosmic distances using Cepheid variable stars.

Edwin Hubble

Edwin Hubble

Discoveries

• Used Leavitt's work to measure distances to galaxies.

• Demonstrated that the universe extends beyond the Milky Way.

• Found evidence that the universe is expanding.

Timeline for Review

1. Ancient civilizations observe the sky.

2. Aristotle proposes geocentric model.

3. Aristarchus proposes heliocentric model.

4. Ptolemy strengthens geocentrism.

5. Copernicus revives heliocentrism.

6. Galileo provides telescope evidence.

7. Tycho Brahe collects precise data.

8. Kepler develops laws of planetary motion.

9. Newton explains gravity and motion.

10. Einstein develops relativity.

11. Henrietta Leavitt develops distance measurements.

12. Hubble discovers galaxies and the expanding universe.

Key Terms

• Astronomy: Study of celestial objects and space.

• Constellation: Pattern of stars seen from Earth.

• Geocentric: Earth-centered model.

• Heliocentric: Sun-centered model.

• Ellipse: Oval-shaped orbit.

• Relativity: Einstein's theory of space, time, and gravity.

• Expanding Universe: Galaxies are moving away from one another.

Exam Essentials

• Aristotle → Geocentric model.

• Aristarchus → Heliocentric model.

• Copernicus → Modern heliocentric revival.

• Galileo → Telescope evidence.

• Tycho Brahe → Accurate observations.

• Kepler → Elliptical orbits.

• Newton → Gravity and motion.

• Einstein → Relativity.

• Henrietta Leavitt → Cosmic distance measurements.

• Hubble → Expanding universe.