Mid Term Flashcards
Celestial Sphere
an imaginary sphere of which the observer is the center and on which all celestial objects are considered to lie
-Naked-eye observations treat all stars at the same distance
Models and Science
The celestial sphere is a model and It provides a means to enhance our understanding of nature
Constellation
Fixed arrangement of stars that can resemble, animals, objects and mythological figures
-as months proceed they move positions
Daily Motion
This can be explained by the rotation of the celestial sphere
Examples
– Sun, Moon, planets, and
stars rise in the east and
set in the west
– Due to the Earth’s
rotation
Annual Motion
A given star rises 3 minutes 56 seconds earlier each night and is caused by the Earth’s motion around the Sun, the result of the projection
-Yearly Motion”
– Due to the Earth’s
revolution
The Ecliptic
The path of the Sun through the stars on the celestial sphere
The Zodiac
The belt shaped region of the sky surrounding the ecliptic passes primarily through twelve constellations
What causes seasons
Not caused by the sun’s proximity, but caused by the tilt of the earth’s axial tilt at 23.5 degrees
The Ecliptic’s Tilt
The tilt of the earth’s rotation axis causes the ecliptic not be aligned with the celestial equator
Solstices and Equinoxes
Points on horizons where the sun rises and sets change throughout the year
Solstices (about June 21 and December 21) are when the sun rises at the most extreme north and south points
Equinoxes (equal day and night about March 21 and September 23) are when the sun rises directly east
The Sun’s Changing Position
Sun moves north and south of the celestial equator during the year, causing the sun to not rise due east or west on most day
-The shift of the Sun’s position is particularly obvious near the equinoxes, when the Sun’s position on the horizon shifts by almost its own diameter
each day
Path of Sun Changes with Latitude
-The path the Sun follows each day can be quite different at different latitudes
The Moon
Rises east and sets west
Phases of the Moon
Span of 30 days
Phases: New -> Waxing Crescent
First quarter -> Waxing Gibbous
Full -> Waning Gibbous
Third Quater -> Waning Crescent
Eclipses
Occurs when the sun, earth, and moon are directly in line
Solar Eclipse
Occurs when the moon passes between the sun and earth, the moon casts it shadow on the earth
Solar Eclipse from Space
Casts a umbra and a penumbra
-Umbra the dark center
-Penumbra the outer
Lunar Eclipse
Occurs when the earth passes between the sun and moon, giving the moon a red color
What causes a red moon
The earth’s atmosphere bends some sunlight into the shadow and the interactions with particles in the air remove the blue light
Rarity of Eclipses
Twice a year the moon’s orbit will pass through the sun called eclipse seasons
Eclipse Periods
Do not occur every 30 days since the moon’s orbit is tipped relative to the earth’s orbit
The Scientific Method
A process that describes how scientist go about observing, experimenting, explaining and predicting
1: Make observations
2: Analyze Results
3: Choose simplest theory or develop new theory
4: Propose higher-precision experiment or make predictions
5: Prepare test of new theory
6: back to step one
Ptolemy and Retrograde motion
Used to explained the retrograde motion of the planets using epicycles and dererents
Nicolaus Copernicus
Published De revolutionibus orbium coelestium, which his theory of planets had circular orbits around the sun was flawed and corrected by Johannes Kepler
Tycho Brahe
Created a theory called Tychonic system, where the Earth is stationary, with the sun and moon revolving around, while other planets revolve around the sun
Johannes Kepler
Tried to mathematically predict the planetary orbits and was wrong.
-He deduced his three laws of planetary motion based on Tycho’s observations
Galileo Galilei
Formulated his law of falling bodies, which all objects fall at the same rate
-created the first telescope and made discoveries that contradicted Aristotle and the Roman Catholic Church
Isaac Newton
Created a reflecting telescope and discovered white light is a mixture of all colors
-Calc dude
Average Distance of the Planets From the Sun
Measurement au: modern
Mercury: 0.39
Venus: 0.72
Earth: 1
Mars: 1.52
Jupiter: 5.2
Saturn: 9.54
Uranus: 19.19
Neptune: 30.06
Parallax
Nearby objects are viewed at different angles, from different places and used by astronomers, surveyors and sailors to determine distance
Ellipses
-Oval shaped
The sum of the distances to the foci is a constant
Can have different eccentricities between the range 0 to 1
Kepler’s First Law - The Law of Ellipses
The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus.
Kepler’s Second Law - The Law of Equal Areas
An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time
Kepler’s Third Law - The Law of Harmonies
the ratio of the squares of the periods to the cubes of their average distances from the sun is the same for every one of the planets
Units of Astronomical Distance
(au) astronomical unit is the average distance between earth and the sun
(ly) light-year distance that light travels in a year through a vacuum
(pc) parsec is the distance at which two objects separated by 1 au make an angle of 1 arcsec
Newton’s First Law - The law of Inertia
The law of Inertia
-An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force
Newton’s Second Law - The Force law
The Force law
-the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object
Newtons Third Law - The Law of Action and Reaction
- every interaction, there is a pair of forces acting on the two interacting objects