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everything Flashcards

(42 cards)

1
Q

What are epicycles in the context of the ancient geocentric model?

A

Small circles in which celestial bodies moved while simultaneously making a larger circle around the Earth.

Proposed by Claudius Ptolemy to explain planetary motion.

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2
Q

What phenomenon do epicycles help to account for?

A

Retrograde motion.

Retrograde motion is when planets appear to move backwards across the sky.

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3
Q

What two components make up Ptolemy’s model for predicting planetary positions?

A
  • 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.

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4
Q

What were some limitations of the geocentric model?

A
  • 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.

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5
Q

Who proposed the Heliocentric Model and when?

A

Nicolaus Copernicus in the 16th century.

The Heliocentric Model placed the Sun at the center of the Universe.

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6
Q

What was the significance of the Heliocentric Model?

A

It marked the beginning of modern astronomy.

This model was later confirmed by astronomers like Galileo and Kepler.

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7
Q

What belief was the Geocentric Model based on?

A

The Earth was the center of the Universe.

This belief was held by earlier civilizations such as Egyptians, Babylonians, and Greeks.

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8
Q

Who were notable proponents of the Geocentric Model?

A
  • Aristotle
  • Ptolemy

Greek philosophers who supported the idea that celestial bodies orbited around the Earth.

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9
Q

What did Ptolemy’s geocentric model propose about planetary motion?

A

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.

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10
Q

What do ancient monuments indicate about early humans?

A

They had a good understanding of the patterns of the heavens

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11
Q

What significance might the celestial alignment of ancient structures have had?

A

Agricultural planning, religious events, measurement of time

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12
Q

What can studying ancient monuments and their alignments help us understand?

A

The astronomical knowledge and beliefs of ancient civilisations

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13
Q

What is atmospheric extinction?

A

The scattering and absorption of electromagnetic radiation by the atmosphere

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14
Q

How does atmospheric extinction affect celestial objects at different altitudes?

A

Objects near the horizon are affected more than those at the zenith

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15
Q

What phenomenon causes light from celestial objects to bend as it enters Earth’s atmosphere?

A

Refraction

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16
Q

What effect does refraction have on celestial objects?

A

Makes the object appear higher in the sky than it actually is

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17
Q

When is the effect of refraction more pronounced?

A

When the object is closer to the horizon

18
Q

What is scintillation?

A

The fluctuation in star brightness caused by the Earth’s atmosphere

19
Q

What causes scintillation?

A

Pockets of air at slightly different temperatures

20
Q

What does skyglow refer to?

A

The brightening of the night sky caused by artificial light pollution

21
Q

What impact does skyglow have on visibility?

A

It hampers visibility of faint celestial objects

22
Q

What does the term astronomical seeing refer to?

A

The blurring and twinkling of astronomical objects

23
Q

What causes astronomical seeing?

A

Turbulence in Earth’s atmosphere

24
Q

How do rapid changes in air density affect visibility?

A

Create an effect like viewing objects through a rippling pool of water

25
What weather conditions significantly impact astronomy?
Clouds, winds, and humidity
26
Fill in the blank: Atmospheric extinction diminishes the intensity of _______.
celestial objects
27
What is gravitation?
A physical force that pulls bodies towards each other.
28
Who first defined the law of universal gravitation?
Physicist Isaac Newton.
29
What does the law of universal gravitation state?
Every particle of matter in the universe attracts every other particle.
30
How is the strength of gravitational force calculated?
It is directly proportional to the product of the masses and inversely proportional to the square of the distance between their centres.
31
What is the formula for the law of universal gravitation?
F = G(m1*m2)/r^2.
32
In the formula F = G(m1*m2)/r^2, what does F represent?
The force of attraction between the bodies.
33
In the formula F = G(m1*m2)/r^2, what do m1 and m2 represent?
The masses of the two bodies.
34
In the formula F = G(m1*m2)/r^2, what does r represent?
The distance between the centres of the two bodies.
35
In the formula F = G(m1*m2)/r^2, what does G represent?
The gravitational constant.
36
What drives planetary motion?
The gravitational attraction between a planet and the star it revolves around.
37
What shape does a planet's orbit take?
An ellipse.
38
What are the focus points of an ellipse in the context of a planet's orbit?
One focus is the star around which the planet orbits.
39
When is a planet's speed fastest in its orbit?
When it is closest to the star (at perihelion).
40
When is a planet's speed slowest in its orbit?
When it is farthest from the star (at aphelion).
41
What principle explains the varying speed of a planet in its orbit?
The conservation of angular momentum.
42