Podcast
Questions and Answers
Which observation made by Anaxagoras supported the idea of a spherical Earth?
Which observation made by Anaxagoras supported the idea of a spherical Earth?
- Stars appeared higher in the sky when traveling north.
- The phases of the moon were directly related to the Earth's position.
- Ships disappeared hull first over the horizon.
- The Earth's shadow during a lunar eclipse was circular. (correct)
How did Aristotle use the position of the North Star to argue for a spherical Earth?
How did Aristotle use the position of the North Star to argue for a spherical Earth?
- The North Star was only visible from certain longitudes.
- The North Star's brightness changed with the seasons.
- The North Star disappeared below the horizon as one traveled south.
- The height of the North Star in the sky varied depending on the observer's location. (correct)
Eratosthenes used the differing angles of shadows in Alexandria and Syene to calculate what property of Earth?
Eratosthenes used the differing angles of shadows in Alexandria and Syene to calculate what property of Earth?
- The density of Earth's core
- The circumference of Earth (correct)
- The tilt of Earth's axis
- The distance to the moon
Why were circles and spheres considered 'perfect forms' by Pythagoras, influencing his view of Earth's shape?
Why were circles and spheres considered 'perfect forms' by Pythagoras, influencing his view of Earth's shape?
During a lunar eclipse, what shape of shadow would a flat, disc-shaped Earth cast on the Moon?
During a lunar eclipse, what shape of shadow would a flat, disc-shaped Earth cast on the Moon?
Besides lunar eclipses, what other observation did Aristotle use to support the idea of a spherical Earth?
Besides lunar eclipses, what other observation did Aristotle use to support the idea of a spherical Earth?
Before telescopes, what led astronomers to understand astronomical phenomena?
Before telescopes, what led astronomers to understand astronomical phenomena?
What aspect of Earth's shape is described by the term 'oblate spheroid'?
What aspect of Earth's shape is described by the term 'oblate spheroid'?
How did the understanding of Earth's shape transition from Pythagoras to the time of Apollo 8's 'Earthrise' photograph?
How did the understanding of Earth's shape transition from Pythagoras to the time of Apollo 8's 'Earthrise' photograph?
If Eratosthenes measured the distance from Alexandria to Syene as 5000 stadia, and one stadium is 0.167 km, what was the distance in kilometers?
If Eratosthenes measured the distance from Alexandria to Syene as 5000 stadia, and one stadium is 0.167 km, what was the distance in kilometers?
What was the key insight that allowed Eratosthenes to estimate Earth's circumference with reasonable accuracy?
What was the key insight that allowed Eratosthenes to estimate Earth's circumference with reasonable accuracy?
Tycho Brahe's meticulous astronomical observations primarily contributed to what advancement?
Tycho Brahe's meticulous astronomical observations primarily contributed to what advancement?
What fundamental belief about celestial motion did Kepler's Laws, derived from Brahe's data, challenge?
What fundamental belief about celestial motion did Kepler's Laws, derived from Brahe's data, challenge?
Which early philosopher's idea about a spherical Earth was circulated more widely due to his dialogues?
Which early philosopher's idea about a spherical Earth was circulated more widely due to his dialogues?
What did Eratosthenes use to calculate the circumference of the Earth?
What did Eratosthenes use to calculate the circumference of the Earth?
Flashcards
Earth's Shape
Earth's Shape
The shape of the Earth is best described as an oblate spheroid, which is a sphere that is slightly flattened at its poles and bulging at the equator due to the centrifugal force caused by the Earth's rotation.
Pythagoras's Idea
Pythagoras's Idea
He believed circles and spheres to be perfect forms and suggested that Earth should be a sphere just like that of the Moon's shape.
Anaxagoras's Observation
Anaxagoras's Observation
He supported Pythagoras' idea of a spherical Earth and observed that the Earth's shadow during a lunar eclipse was circular, which only a sphere could consistently cast.
Plato's Belief
Plato's Belief
Signup and view all the flashcards
Aristotle's Evidence
Aristotle's Evidence
Signup and view all the flashcards
Eratosthenes's Calculation
Eratosthenes's Calculation
Signup and view all the flashcards
Lunar Eclipse Shadow
Lunar Eclipse Shadow
Signup and view all the flashcards
Ships Disappearing Hull First
Ships Disappearing Hull First
Signup and view all the flashcards
Varying Angle of the North Star
Varying Angle of the North Star
Signup and view all the flashcards
Study Notes
- Earth is not the center of the universe.
- Earth is spherical.
Lesson Outcomes
- Learn how the Greeks knew that the Earth is spherical.
- Learn about astronomical phenomena known to astronomers before telescopes.
- Learn how Brahe's innovations and data in astronomy paved the way for Kepler's laws of planetary motion.
Earth's Shape
- Earth's shape is a sphere, specifically an oblate spheroid.
- Apollo 8's photo of Earth is known as "Earthrise".
Pythagoras (500 BC)
- Pythagoras believed circles and spheres are perfect forms.
- He suggested that Earth should be a sphere resembling the Moon's shape.
Anaxagoras
- Anaxagoras supported Pythagoras' idea of a spherical Earth.
- Anaxagoras observed that the Earth's shadow during a lunar eclipse is circular.
- A sphere can only cast a circular shadow.
Plato
- Plato adopted the idea of a spherical Earth in his 4th and final dialogue Phaedo.
- Idea was presented in a crowd which led to a broader circulation 400 BC.
Aristotle
- Aristotle presented ideas about a spherical Earth.
- He based it on the position of the North Star.
- As well as phases of the Moon, the shape of the Sun and Moon, and ship's disappearance at the horizon.
Eratosthenes
- Eratosthenes argued that the Earth is spherical.
- He concluded this through the difference of the shadows cast at Alexandria and Syene at the same time of day.
- Eratosthenes calculated the circumference of the Earth.
- The measured distance from Alexandria to Syene was 5000 stadia north.
- One stadium is about 0.167 km today.
- Alexandria to Syene has a curvature of 7 degrees.
- There are 360 degrees circumference.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
