Astronomy Test 1 Objectives Flashcards
Name the five north circumpolar constellations and tell what each represents.
Ursa Major - the Great Bear, the Big Dipper
Ursa Minor - the Little Bear, the Little Dipper
Cassiopeia - the Queen
Cepheus - the King
Draco - the Dragon
On an unlabeled star chart, draw in the connecting lines to identify the five north circumpolar constellations. On the diagram, label the positions of Polaris, Thuban, and Mizar.
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Describe the geocentric theory of the universe held by many early Greeks.
Earth is motionless at the center of the universe.
The stars are attached to a celestial sphere that rotates daily around the Earth.
There are 7 objects (Greek: “planet” = wanderer) (Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn) that moves in front of the celestial sphere.
Name the 7 objects that can be seen with the eye to move against the background stars. With which day of the week is each identified?
Sun - Sunday Moon - Monday Mars - Tuesday Mercury - Wednesday Jupiter - Thursday Venus - Friday Saturn - Saturday
List the astronomical contributions of the ancient Greek philosophers Aristotle, Eratosthenes, Hipparchus, and Ptolemy.
Aristotle - concluded that Earth was round because always cast round shadow when it eclipses the moon
geocentric Earth
motion requires a continued push or pull
Eratosthenes - determined diameter of the Earth
Hipparchus - catalogued the location of about 850 stars
divided brightness of stars into 6 groups
measured the length of the year to within minutes of today’s value
developed a method to predict lunar eclipses
Ptolemy - wrote the Almagest, a summary of astronomy
developed a geocentric model that explained retrograde motion
Describe the Ptolemaic model of the universe. What is the retrograde motion?
planets move in perfect circular orbits around a motionless Earth
planets orbit on small circles (epicycles) and revolve on large circles (deferents)
Describe the contributions to modern astronomy of Nicolaus Copernicus, Tycho Brahe, Johannes Kepler, Galileo Galilei, and Isaac Newton.
Copernicus - 1. Stars are stationary, therefor Earth rotates
2. Heliocentric model
3. Planets move in perfect circles at constant speeds
Brahe - made careful observations that were good to within 1-2 min of arc (could not detect parallax)
Kepler - Kepler’s (3) Laws of Planetary Motion
Galileo Galilei - “Father of Modern Science”; discovered inertia (no force necessary to keep Earth/planets in motion); made first astronomical telescope and with it discovered: Jupiter’s moons; planets are disks; moon has mountains, craters, darker areas; Milky Way made up of stars; Sun has dark spots that move; Venus shows a full range of phases
Isaac Newton - invented calculus; invented reflecting telescope; established celestial mechanics; Three Laws of Motion; Law of Universal Gravitation
List and describe the three main obections to the heliocentric model of the universe at the time of Copernicus.
- from theologians - Earth is not at the center (mankind is supposed to be pinnacle of creation)
- counter to “common sense”
-no effects of motion could be observed
3, no parallax effect observed
-stars should move in small closed loops
“Modern” science is often dated from Galileo. Why? List some of Galileo’s significant discoveries.
overthrew authority of Aristotle through observation and experimentation
discovered inertia
advocated the Copernican model because of its simplicity and logic
made first astronomical telescope
-Jupiter’s moons
-planets are disks,not points of light like the stars
-Moon has mountains, craters, darker areas - Maria
- Milky Way is made up of many stars
- Sun has dark spots that move around the Sun
-Venus shows a full range of phases and appears to vary in size
-expected in Copernican (heliocentric) model
Describe Kepler’s three laws of planetary motion.
What is meant by the eccentricity of a planet’s orbit?
Given the distance to a planet in AU, calculate the period of its orbit.
- The planets orbit the Sun in ellipses, with the Sun at one focus.
- A line joining the Sun and a planet sweeps out equal areas in equal times.
- The square of the period of revolution (P) is proportional to the cube of the average distance (R) of the planet from the Sun.
Eccentricity is the ratio of the distance between the foci of the orbit to the length of the major axis.
Describe/apply Newton’s three laws of motion.
- Distinguish between mass and weight.
- Describe why a light object falls at the same rate as a heavy object, neglecting the effects of air resistance.
- Every object at rest remains at rest or every object in motion remains in uniform motion in a straight line unless acted upon by some outside force.
- The acceleration given to an object is equal to the net force applied to it divided by its mass.
- For every action there is an equal and opposite reaction.
Mass is a measure of the inertia of an object and is the same everywhere. Weight is a measure of the gravitational force of attraction on an object and depends on where it is measured.
Because F/m=a, and 10F/10m=a.
Describe/apply Newton’s Law of Universal Gravitation.
Every object in the universe attracts every other object with a force that is directly proportional to their masses and inversely proportional to the square of the distance between them.
F=G((m1m2)/rsquared) double mass doubles weight
double mass, leave r the same, double weight
Describe the difference between rotation and revolution. What time periods do each of these produce for the Earth?
rotation: spinning on its axis; revolution: orbiting, i.e. Earth’s movement around the Sun
day and night; seasons
What is a solar day and a sidereal day, and describe why one is different than the other.
avg time from noon to noon; avg. ~ 24 hours
Sidereal day is the rotation of the Earth with respect to a star other than our Sun. 23 hrs 56 min 4 sec
Describe some characteristics of the Earth’s orbit around the Sun (e.g., elliptical shape, perihelion, aphelion, avg. distance from the Sun, etc.).
elliptical shape - two foci as opposed to a circle’s one
perihelion - nearest to sun, 91.5 mil miles, Jan. 3
apheliond - furthest from sun, 94.5 mil miles, July 4
avg. distance from Sun 93 mil miles
