Unit 6: Sir Isaac Newton Flashcards
(128 cards)
1
Q
What was the dominant belief about Earth’s position in the universe for most of human history?
A
That Earth was stationary and everything in the sky revolved around it (geocentric model).
2
Q
Which early thinkers supported a heliocentric view before Copernicus?
A
The early Pythagoreans and Aristarchus.
3
Q
Who were the key figures in shifting the belief from geocentrism to heliocentrism?
A
Copernicus, Brahe, Kepler, and Galileo.
4
Q
Why was the Catholic Church unable to silence all scientific progress?
A
Because its influence wasn’t global, especially not in 17th-century England.
5
Q
Why did King Henry VIII separate from the Catholic Church?
A
To divorce his wife Catherine of Aragon, which the Pope refused.
6
Q
What religion did Henry VIII establish in England?
A
Protestantism.
7
Q
How did Queen Elizabeth I impact scientific progress in England?
A
Her reign promoted peace, stability, expansion, and a culture that valued knowledge and science.
8
Q
Who began to fill the void in cosmological education after Aristotle was disproven?
A
René Descartes.
9
Q
What philosophical stance did Descartes take about knowledge?
A
That it should be doubted and rebuilt on irrefutable truths.
10
Q
What principle about space did Descartes propose?
A
That empty space does not exist.
11
Q
What did Descartes call the substance that fills all space?
A
The ether.
12
Q
How did Descartes believe planetary motion was driven?
A
By celestial bodies disturbing the ether and creating vortices.
13
Q
What is the Cartesian system?
A
A model where planets float in a spinning fluid (ether) around the Sun and other stars.
14
Q
How did Descartes explain moons?
A
As smaller bodies caught in planetary vortices.
15
Q
What idea about stars did Descartes propose?
A
That each star is like our Sun, with its own planetary system.
16
Q
What caused Newton to reject Descartes’ theory?
A
The model couldn’t accurately predict planetary motion.
17
Q
What modern parallel exists to Descartes’ idea of ether?
A
Einstein’s concept of spacetime as a fabric.
18
Q
By the late 17th century, what cosmological view was common in universities?
A
The Cartesian model of the universe.
19
Q
How did Descartes differ from Kepler in explaining planetary motion?
A
Descartes used a fluid vortex model; Kepler used invisible forces like magnetism.
20
Q
What was the Royal Society’s main goal in 17th century England?
A
To arrive at scientific conclusions using the scientific method through repeated experiments.
21
Q
Who was the first curator of experiments for the Royal Society?
A
Robert Hooke.
22
Q
What significant law in physics is Robert Hooke known for?
A
Hooke’s Law, which deals with the force applied by springs.
23
Q
What term did Robert Hooke coin in biology?
A
The term ‘cell’.
24
Q
What did Robert Hooke use to model celestial motion in his experiments?
A
A pendulum with a bob representing a planet and a fulcrum representing the Sun.
25
What was the title of Robert Hooke's 1674 publication?
An Attempt to Prove the Motion of the Earth from Observations.
26
What did Hooke try to detect to prove Earth's motion?
Stellar parallax.
27
What concept did Hooke propose in his 1674 article?
Gravitational attraction as a universal force responsible for motion.
28
According to Hooke, how does gravitational force vary with distance?
Gravitational attraction increases as the distance to the object decreases.
29
What significant shift in thought did Hooke's theory contribute to?
The idea that the same physical laws apply on Earth and in space.
30
When was Isaac Newton born?
1643, the same year Galileo died.
31
What major mathematical field did Newton invent?
Calculus.
32
What is calculus used for?
Describing how quantities change, like motion and velocity.
33
What is a derivative in calculus?
It calculates the slope or the rate of change of a function.
34
Why is calculus important for astronomy?
It allows precise computation of planets' positions and speeds over time.
35
What was Newton’s first major known scientific contribution?
His work on light and optics.
36
What did Newton discover about white light?
It is composed of all the colors of the rainbow.
37
What is the term for the splitting of white light into colors?
Dispersion.
38
What problem does dispersion cause in refracting telescopes?
It causes color fringing and blurring of images.
39
What type of telescope did Newton invent to reduce dispersion?
Reflecting telescope (Newtonian reflector).
40
How does a reflecting telescope work?
Uses mirrors to focus light, minimizing dispersion.
41
What is the advantage of space telescopes like Hubble?
They avoid atmospheric distortion for clearer images.
42
What is the James Webb Space Telescope’s mirror diameter?
6.5 meters.
43
Why are modern telescopes built with mirrors?
Mirrors don't cause dispersion and can be much larger than lenses.
44
What causes stars to appear to twinkle when seen from Earth?
Atmospheric distortion, also called scintillation.
45
Who was Edmund Halley?
A talented English scientist and polymath who made contributions in astronomy and was a member of the Royal Society.
46
Why was the Royal Society important for scientific recognition in 17th century England?
It was the main institution that supported and published scientific research, unless a scientist was independently wealthy.
47
What did Halley do at age 20?
Sailed to St. Helena and created the first comprehensive star map of the southern sky for Europeans.
48
How did Newton get involved with the Royal Society?
His work on light and invention of the reflecting telescope caught their attention, leading to an invitation.
49
What was the main scientific debate involving Hooke and Halley?
They were trying to prove that planetary motion was driven by gravitational attraction from the Sun.
50
What law did Hooke believe gravity followed?
An inverse square law, where gravity weakens with the square of the distance.
51
What is an inverse square law?
A law stating that a force weakens by the square of the distance from its source (1/d^2).
52
How did Hooke demonstrate gravity might follow this law?
He showed that assuming an inverse square law of gravity leads to Kepler’s third law.
53
Why was Hooke's claim disputed?
He claimed he had a full proof but wouldn't show it, leading others to think he was bluffing.
54
What did Newton do with Hooke’s idea?
Used calculus to prove that an inverse square law leads to Kepler’s three laws of planetary motion.
55
What is the Principia Mathematica?
Newton’s major work that includes his proof of gravity and many foundational laws of physics.
56
How did Newton respond to Hooke's demand for credit?
He rewrote the proof in Principia to suggest he derived the law independently.
57
What did Newton do when he became President of the Royal Society?
He banned Hooke and destroyed his portraits, erasing his presence.
58
What major scientific book did Newton publish in 1687?
The Principia Mathematica.
59
What foundational concept did Newton's Principia begin with?
Newton's three laws of motion.
60
What did Newton prove using his three laws of motion?
That gravity obeys an inverse square law and leads to Kepler's three laws.
61
What is Newton’s Cannon thought experiment designed to show?
That gravity is a universal force acting both on Earth and in space.
62
What celestial body did Newton use to compare falling motion on Earth with orbital motion?
The Moon.
63
What key idea about gravity did Newton's Cannon illustrate?
Objects in orbit are in continuous free-fall around a planet.
64
What did Newton conclude about the force that causes falling objects and orbital motion?
They are caused by the same universal force—gravity.
65
According to Newton, what do all orbiting bodies follow?
Kepler's three laws of motion.
66
How did Newton use Kepler’s Third Law to calculate the mass of planets?
By measuring the orbital periods and distances of their moons.
67
What planets did Newton calculate the mass of using Kepler’s Third Law?
Jupiter and Saturn.
68
How massive is Jupiter compared to Earth?
About 300 times more massive.
69
How massive is Saturn compared to Earth?
About 100 times more massive.
70
How did Newton prove that Jupiter and Saturn are gas giants?
By calculating their low densities using mass and volume.
71
What did Newton’s findings suggest about the composition of Jupiter and Saturn?
They must be primarily composed of gas.
72
Why is Saturn famously said to float in water?
Because its density is lower than that of water.
73
What major scientific book did Newton publish in 1687?
Principia Mathematica
74
What law of gravity did Newton prove in the Principia?
The inverse square law of gravity
75
What are Newton's three laws of motion used for in the Principia?
To derive the law of gravity and explain various physical phenomena
76
What is the shape of Earth due to its rotation?
An oblate spheroid
77
What physical force causes the Earth's equatorial bulge?
Centrifugal force due to Earth's rotation
78
Which of Newton's laws explains the centrifugal force?
Newton's Third Law of Motion
79
Why does the Earth wobble or experience axial precession?
Due to the gravitational pull on the Earth's equatorial bulge by the Sun and Moon
80
How long does one cycle of Earth's axial precession take?
Approximately 26,000 years
81
What effect does the equatorial bulge have in a gravitational field?
It causes asymmetric gravitational pull, inducing precession
82
What did Newton use as evidence for Earth's equatorial bulge?
Pendulum clocks tick slower near the equator due to weaker gravity
83
Which mountain is technically closest to space due to Earth’s bulge?
Mount Chimborazo in Ecuador
84
Why do many galaxies and the solar system appear as flat disks?
Because of spinning systems and centrifugal forces
85
What celestial body is the primary source of gravity pulling on Earth?
The Sun
86
What two bodies cause significant gravitational pull affecting Earth's wobble?
The Sun and the Moon
87
What causes the rising and falling of ocean tides?
The gravitational pull of the Moon on Earth's oceans.
88
Where are the highest tides in the world observed?
Bay of Fundy, between New Brunswick and Nova Scotia in Canada.
89
Why do some places have more noticeable tides than others?
Due to local effects like ocean currents and sea floor topography.
90
What did Newton realize about the Moon’s gravitational pull?
It affects Earth and its oceans, pulling the water and creating tides.
91
Why do ocean bulges form both towards and away from the Moon?
Due to the difference in gravitational pull across Earth's surface.
92
What is a tidal force?
The difference between gravitational attraction on Earth's center and at a point on its surface.
93
Why does the side of Earth farthest from the Moon also experience a high tide?
Because the Moon pulls more strongly on the near side, leaving the far side behind.
94
How often does a location on Earth experience high tide?
Approximately every 12 hours, or twice daily.
95
What causes spring tides?
Alignment of the Sun and Moon, increasing gravitational pull on Earth’s oceans.
96
What causes neap tides?
When the Sun and Moon are at right angles, reducing the overall tidal effect.
97
How do spring and neap tides differ in water level?
Spring tides cause higher high tides and lower low tides; neap tides have less extreme tides.
98
Why is the Sun’s effect on tides smaller than the Moon’s?
The Sun is farther from Earth, so its gravitational pull has less tidal effect.
99
What is the monthly cycle of tides driven by?
The Moon’s orbit around the Earth and its alignment with the Sun.
100
Why do we call them 'spring' tides?
Because 'spring' refers to a rise in water levels, not the season.
101
What is the main reason Newton was initially confused by the Moon's orbit?
Newton found that the Moon was sometimes ahead or behind where it should be according to his laws of motion and gravity.
102
What realization helped Newton correctly describe the Moon's motion?
He realized that celestial bodies orbit around the *center of mass* of the system, not the exact center of the more massive body.
103
What is the center of mass?
The center of mass is the average location of all the mass in a system, or the balance point between two bodies based on their masses and distances.
104
How is the Earth-Moon center of mass positioned?
It lies inside the Earth, about 1/82 of the way from the Earth's center to the Moon.
105
Why is the Moon said to orbit the Earth even though it technically orbits the center of mass?
Because the center of mass is still inside the Earth, it's reasonable to say the Moon orbits Earth.
106
What is the teeter-totter analogy used to explain in orbital dynamics?
It's used to visualize how two unequal masses balance each other and where the center of mass lies between them.
107
In a system with two equal-mass bodies, where is the center of mass?
Exactly halfway between them.
108
What effect does the Moon have on the Earth due to the shared center of mass?
The Earth also "wobbles" slightly, orbiting around the shared center of mass every 30 days.
109
How does the Sun respond to Jupiter's gravitational pull?
The Sun makes a tiny orbit (or wobble) around the center of mass of the Sun-Jupiter system, slightly off-center from the Sun’s core.
110
Why is the Sun’s wobble significant in modern astronomy?
Detecting similar wobbles in other stars helps astronomers identify planets orbiting those stars.
111
What did Newton use his understanding of motion and gravity to explain?
Kepler's laws, tides, Earth's shape, Moon's orbit.
112
What event in 1680 helped demonstrate Newton’s theories?
The appearance of a great comet.
113
How was the great comet of 1680 first discovered?
Through a telescope as a moving point of light.
114
What is notable about the direction of a comet's tail?
It always points away from the Sun due to the solar wind.
115
What did Newton conclude from the comet’s path?
Comets follow elliptical orbits and obey Kepler’s laws.
116
Why do comets appear for only a short time?
They’re only visible when near the Sun and heating up.
117
What did Newton’s sketch of the comet show?
The elliptical path with the Sun at one focus and tail directions.
118
Why are comets' appearances considered unpredictable?
Because many have extremely long orbits, sometimes thousands of years.
119
What did Edmond Halley use to predict the return of a comet?
Historical comet sightings and Newton's laws of gravity.
120
Which comet did Halley predict would return?
The comet that became known as Halley’s Comet.
121
When did Halley predict the comet would return?
December 1758.
122
What motion did all four historical comet sightings have in common?
Retrograde motion.
123
What proved the universality of gravity according to Halley’s prediction?
The comet reappeared as predicted in December 1758.
124
What is the orbital period of Halley’s Comet?
Approximately 76 years.
125
When was Halley’s Comet first photographed?
In 1910.
126
What did the 1986 spacecraft mission to Halley’s Comet reveal?
Comets are large blocks of rock and ice, with gas tails from vaporized material.
127
When is Halley's Comet expected to return next?
In 2061.
128
How did Halley determine the comet sightings were the same object?
By identifying similar descriptions and 76-year intervals between sightings.
