everything Flashcards
(42 cards)
What are epicycles in the context of the ancient geocentric model?
Small circles in which celestial bodies moved while simultaneously making a larger circle around the Earth.
Proposed by Claudius Ptolemy to explain planetary motion.
What phenomenon do epicycles help to account for?
Retrograde motion.
Retrograde motion is when planets appear to move backwards across the sky.
What two components make up Ptolemy’s model for predicting planetary positions?
- Epicycle (small circle)
- Deferent (large circle)
The model required the speed of a planet on its epicycle to be linked to the speed of its deferent.
What were some limitations of the geocentric model?
- Could not accurately explain the varying brightness of planets
- Could not explain retrograde motion without complex mechanisms
- Required constant adjustments and exceptions
These limitations led scientists to question the validity of the geocentric model.
Who proposed the Heliocentric Model and when?
Nicolaus Copernicus in the 16th century.
The Heliocentric Model placed the Sun at the center of the Universe.
What was the significance of the Heliocentric Model?
It marked the beginning of modern astronomy.
This model was later confirmed by astronomers like Galileo and Kepler.
What belief was the Geocentric Model based on?
The Earth was the center of the Universe.
This belief was held by earlier civilizations such as Egyptians, Babylonians, and Greeks.
Who were notable proponents of the Geocentric Model?
- Aristotle
- Ptolemy
Greek philosophers who supported the idea that celestial bodies orbited around the Earth.
What did Ptolemy’s geocentric model propose about planetary motion?
Each planet moved in a small circle (epicycle) which moved along a larger circle (deferent) centered around the Earth.
This model aimed to explain the observed retrograde motion of planets.
What do ancient monuments indicate about early humans?
They had a good understanding of the patterns of the heavens
What significance might the celestial alignment of ancient structures have had?
Agricultural planning, religious events, measurement of time
What can studying ancient monuments and their alignments help us understand?
The astronomical knowledge and beliefs of ancient civilisations
What is atmospheric extinction?
The scattering and absorption of electromagnetic radiation by the atmosphere
How does atmospheric extinction affect celestial objects at different altitudes?
Objects near the horizon are affected more than those at the zenith
What phenomenon causes light from celestial objects to bend as it enters Earth’s atmosphere?
Refraction
What effect does refraction have on celestial objects?
Makes the object appear higher in the sky than it actually is
When is the effect of refraction more pronounced?
When the object is closer to the horizon
What is scintillation?
The fluctuation in star brightness caused by the Earth’s atmosphere
What causes scintillation?
Pockets of air at slightly different temperatures
What does skyglow refer to?
The brightening of the night sky caused by artificial light pollution
What impact does skyglow have on visibility?
It hampers visibility of faint celestial objects
What does the term astronomical seeing refer to?
The blurring and twinkling of astronomical objects
What causes astronomical seeing?
Turbulence in Earth’s atmosphere
How do rapid changes in air density affect visibility?
Create an effect like viewing objects through a rippling pool of water
