Exam 1 Study Guide Flashcards
A scientific hypothesis must be…
testable and falsifiable (never provable)
Stars circle the same location every…
23 hours, 56 minutes, 04 seconds
The Sun returns to the same approximate location every…
24 hours
Motion of the Sun and Moon is ______ with respect to the stars
East
Mars, Jupiter and Saturn also move __________ with respect to the stars, but _____________ when opposite the sun.
Eastward (most of the time), Westward
Mercury and Venus move _________, but _________ after maximum Eastward elongation (ie. as far East as they are going to go)
Eastward (most of the time), Westward
The whole sky is marked out in a grid like longitude and latitude, but called…
Right Ascension and Declination
The angle between a line drawn from an observer to an object and a second line drawn from the observer to a different object is the _________ of those objects
angular separation
The angle between a line drawn from an observer to one end of an object and a second line drawn from the observer to the other end of the object is the _________ of the object
angular size
Trivium
The beginning studies of medieval universities: grammar, local, and rhetoric
Quadrivium
Medieval preparatory work for philosophy and theology: arithmetic, astronomy, geometry, and music
The stars appear to circle the star _______ in one _____________
Polaris, sidereal day
An incorrect model used to understand motions is the _________, which is a transparent sphere with Earth spinning inside
Celestial Sphere
The Ecliptic
The pathway that the sun takes (1 year); tilt of 23/5%
The moon follows a different path near the ecliptic which takes about __________ to make an entire trip, with respect to the stars
27 days
Solar Eclipses occur when….
The Sun and Moon align and the Moon is on the ecliptic
Lunar Eclipses occur when…
The Sun and Moon are opposite and the Moon is near the Ecliptic
Retrograde Motion
An APPARENT change in the movement of the planet through the sky. It is not REAL in that the planet does not physically start moving backwards in its orbit. It just appears to do so because of the relative positions of the planet and Earth and how they are moving around the Sun.
The sun ___________ its own light, but the moon only ________, allowing us to understand lunar phases from the relative positions of the sun and moon
emits its own light, reflects
Order of Moon Phases
New Moon First Quarter Full Moon Third Quarter New Moon
Because the ecliptic and celestial equator are not the same, the sun is sometimes _______ in the sky at noon, sometimes _______
higher, lower
zenith
point directly above in the sky
Solstices
The points farthest North and South in the Sun’s travels along the ecliptic
Equinoxes
The Sun’s crossings of the celestial equator
Seasons occur because…
of the changing angle with which the sunlight hits the Earth
Stars appear to circle a fixed point each sidebar day from ____ to ____
East, West
The ____ and ____circle more or less with the _____, but take longer to complete the circle
Sun, Moon, stars
The _____ and _____ appear further ____ each day with respect the stars
Sun, Moon, east
The Sun and Moon also move ____ and ____ as they migrate Eastward
North, South
The planets usually appear further ___ each day, but occasionally appear further _____
East, West
Occasional retrograde motion always occur at opposition for ___, _____, and _____
Mars, Jupiter, and Saturn
Occasional retrograde motion always occur after maximum eastward elongation for _____ and _______
Mercury and Venus
The planets do not move the same _________ each day
Angular distance
The phases of the moon are due to…
Differing illumination
The seasons are due to the changing _______ position of the sun
North-South
Evidence for “Fixed Earth”
- We throw something up, it comes back down in the same place
- The stars do not show visible parallax (changing apparent position due to our changing point of view)
The Influence of Aristotle
- All motion in the heavens is uniform circular motion.
(otherwise a void is opened, which is impossible). - The objects in the heavens are made from perfect spheres and cannot change their intrinsic properties (e.g., their brightness).
- The Earth is at the center of the Universe.
Predictions of the Geocentric Model
- Mars, Jupiter and Saturn should be brighter during retrograde, since they are closer at that time
- Mercury and Venus, if illuminated by the sun, should always appear in crescent/new phase.
- Stars should show no parallax
Difference between Geocentric Model and Heliocentric Model:
Geo = Earth is center of universe Helio = Sun is center of universe
Difficulties with Copernican Model
The moon still went around the earth, requiring 2 centers of motion, Did NOT work as well as the geocentric model, because it used perfect circles, Whether it was “pleasing to the mind” was a matter of opinion. It still had multiple circles to get positions right
Kepler’s Laws
Law 1: (1609) The orbit of each planet is an ellipse, with the sun at one focus.
Law 2: (1609) A line drawn from a planet to the sun sweeps out equal areas in equal times.
Law 3: (1618) The square of the orbital period of a planet is directly proportional to the cube of its average distance from the sun.
Kepler’s Law Equation
p squared/a cubed = k
Kepler’s Law Explained
P = period of time A = distance Au = astronomical unit
Stellar Motion Photos
90 degrees = horizontal
0 degrees = vertical
45 degrees = slanted
Velocity
the change in position of an object with respect to time
Acceleration
the change in velocity of an object with respect to time
Law 1: Inertial Law
A body at rest or moving with constant velocity reminds in that state until upon by a force
Law 2: Force Law
A body acted upon by a force will change its velocity. The acceleration will be in the direction of the force applied and directly proportional to the force applied, but inversely proportional to the body’s mass
Law 3: Reaction Law
For every applied force, a force of equal size but opposite direction arises
Parallax
the effect whereby the position or direction of an object appears to differ when viewed from different positions, e.g. through the viewfinder and the lens of a camera
