Geo vs Helio, Light Flashcards
What does Foucault’s pendulum prove?
Earth is rotating around its axis.
Explain Occam’s razor.
When two hypothesis can explain the available data, the hypothesis requiring the fewest new assumptions should be favoured.
What is the direct motion of the Sun, Moon and planets with respect to the background stars?
Move eastward regardless of their rising in the East and setting in the West.
What is retrograde motion?
When planets appear to move westward for a few days.
How does geocentric model explain epicycles?
Each planet moves in small circles called epicycles, which at the same time moves around a larger circle called deferent.
Why is the geocentric solution to retrograde motion bad?
It treats each planet independently, there is no model for which an underlying physical principle can be applied.
Differentiate between the synodic period and the sidereal period.
Synodic Period is the time that elapses between two successive identical configurations as seen from Earth.
Sidereal period is the true orbit period of a planet, time it takes to complete one full orbit around the sun.
Where/what are the following?
(a) Oppositon
(b) Inferior Conjunction
(c) Superior Conjunction
(d) Conjunction.
(a) A superior planet is highest in the sky at midnight, Earth is between planet and star.
(b) An inferior planet here cannot be seen at night. Planet is between Earth and sun.
(c) An inferior planet here cannot be seen. Sun is between Earth and planet.
(d) A superior planet cannot be seen, Sun is between Earth and planet.
T or F. The synodic period is longer than the sidereal period.
True.
What is greatest western and greatest eastern elongation?
An inferior planet at these points is at its maximum angular distance from the sun.
Kepler’s first law of planetary motion.
Each planet’s path around the Sun is an ellipse with the Sun at one focus of the ellipse.
Explain parallax.
The apparent shift in the position of a nearby object against the background of stars when observed from different vantage points.
Formula for eccentricity.
e = c / a
where c = distance between foci, divided by length of semi major axis.
Kepler’s 2nd Law of Planetary Motion.
A planet moves along its elliptical path with a speed that changes in such a way that a line from the planet to the Sun sweeps out equal areas in equal intervals of time.
What is perihelion and apherlion? Give general names.
Perihelion = closest distance to Sun (Periapsis)
Aphelion = farthest distance from Sun (Apoapsis)
Kepler’s Third Law of Planetary Motion.
The Square of a planet’s (or minor body) orbital period is proportional to the cube of its semi-major axis.
P^2 [year] = C x a^3 [au]
C approx 1
year^2 = au^3
T or F. In the heliocentric model, the retrograde motion is explained as the different orbital speed between two planets.
True.
When will Venus be visible at midnight?
Never.
T or F. If we know the orbital period of a comet we can calculate its size.
No
By Kepler’s third law we can get the size of its orbit.
What changes about Kepler’s third law when the body isn’t orbiting the Sun?
C is not 1 when we are not orbiting the sun.
Explain how the faces of Venus proves the heliocentric model.
In Geocentric model:
Dark Venus between Earth and Sun
Light Venus on far side of Earth from Sun.
Would expect these to appear the same angular size.
However full Venus is very small angular size and new (dark) Venus is very big angular size in the sky because full Venus is actually on far side of sun and new Venus is on near side. (Heliocentric model)
Law of universal gravitation.
Two objects attract each other with a force that is directly proportional to the mass of each object and inversely proportional to the square of the distance between them.
Formula for universal gravitation.
F = G (m1 * m2 / r^2)
Formula for escape velocity.
root((2 * G * M) / R)
Define refraction.
Bending of a wave when it enters a medium where its speed is different.
List electromagnetic spectrum from longest wavelength to shortest wavelength.
radio
microwave
infrared
visible
ultraviolet
x-ray
gamma ray
T or F. The heliocentric model is observably proven by both the phases of Mercury and Venus.
True.
Give the values of gravitational constant and plank’s constant.
6.67 * 10^-11
6.625 * 10^-34
Which model predicted that Venus would exhibit nearly all phases (like the Moon)?
The heliocentric model
T or F. Copernicus’s model of the Solar System is the best model because it provided the most accurate positions of the planets than any other heliocentric or geocentric model.
False.
T or F. Mercury must move faster in its orbit than any other planet.
True.
Give approx ranges for main types of electromagnetic radiation in terms of wavelength.
Radio: cm+
Microwaves mm+
Infrared: 700nm+
Visible: 400nm to 700nm
Ultraviolet: 10nm+
X-Rays: 0.01nm+
Gamma Rays: <0.01nm
Order colours in visible spectrum.
ROYGBIV
Electromagnetic radiation with a wavelength of 600nm would be?
visible red light.
What does the wavelength where the peak of the spectrum of a star is located tell us?
The temperature of the star because of Wien’s Law.
Lambda (peak) = Wien’s Constant / Temperature in Kelvin
Which of these was NOT a part of the original Copernican model?
Question options:
Mercury speeds up at perihelion, and slows down at aphelion.
The Earth rotates on its axis once a day.
Mercury must move faster in its orbit than any other planet.
Venus can go all the way around the Sun.
The Sun lies at the center of the solar system.
Mercury speeds up at perihelion, and slows down at aphelion.
