Big Idea Guys
Who first believed the Earth was in the middle of the solar system?
Aristotle
What is a "geocentric" model? What is a "heliocentric" model?
A geocentric model of the solar system has Earth centered.
A heliocentric model of the solar system has the sun centered.
How did Kepler develop his second law of motion? Which planet's orbit was he studying when this was developed?
He compared data of planetary motion at different times along orbits.
He was studying Mars' orbit
What did Ptolemy add to Aristotle's model of the solar system?
Ptolemy expanded upon Aristotle's model by adding planetary motion; adding the orbit of planets around the Earth, called "epicycles".
What is Kepler's First Law of Planetary Motion?
Kepler's first law states that all planets move around the sun in elliptical orbits, where a planet’s path and speed are affected by the gravitational force of the sun. So as a planet travels in a parabolic path, it forms an elliptical orbit with the sun as one of the foci.
Who created the term "epicycles"? What are they?
Ptolemy; they are the orbiting path of planets around the Earth.
Define "elliptical". Who discovered our orbit was elliptical?
similar to an oval shape. Johannes Kepler discovered our orbit was not perfectly circular!
Why do planets change speed as they move along their orbits?
Planets speed up when moving toward the sun due to the sun's pull being generally forward.
Planets slow down when moving away from the sun because the sun's pull is generally backward while moving away
Who was LIKELY the first person to describe gravity as a universal force?
Hint: not Sir Isaac Newton
Robert Hooke
What does "G" represent? (in these formulas)
Bonus: What is it specifically?
G represents the universal gravitation constant.
Bonus: 6.673 x 10-11 N. m2/Kg2
What man discovered the orbit of planets was more elliptical, rather than circular?
Johannes Kepler
Orbital period
the time it takes to complete one orbit
Define perihelion and aphelion
Perihelion: closest point in an orbit to the sun.
Aphelion: point on the orbit that is farthest from the sun.
What part of Ptolemy's model was accurate? Which part was inaccurate?
Planetary order was accurate, besides location of Sun and Earth. Inaccuracies are in planetary motion
State Kepler's Second Law. What is its other name?
Kepler's second law states as a planet moves along its orbit, a line from the sun to the planet sweeps out equal areas over equal amounts of time. Its other name is the "law of areas"
Which scientist made the huge discovery that Earth was NOT at the center of the solar system?
Nicolaus Copernicus discovered Earth and the other planets in the solar system orbit around the sun!
What is inertia?
the tendency of an object to move along a straight path at a constant speed
Give me at least two reasons Copernicus' model was NOT immediately accepted by everyone in his time.
1. it contradicted religious doctrine ("mandates/rules") of the time
2. it demoted Earth to just another planet
3. it contradicted established scientific understanding (geocentric model)
What divides the orbit into its semi-major axes/ a.k.a. "T1" and "T2"? What divides them into the semi-minor axes?
The semi-major axes are divided by the straight line between the perihelion and the aphelion; the perpendicular line through the center of this line creates the semi-minor axes
What relationship is described in Kepler's third law?
Kepler's third law relates the semi-major axes to the orbital period. The square of orbital period is proportional to the cube of the semi-major axis. This works for two objects orbiting the SAME mass.
T2 ∝ a3
Who first realized that gravity was "universal"? What does "universal" mean in this context?
Sir Isaac Newton; "universal" means that gravity is not only a force that applies to Earth, but between ANY two objects with mass.
What is "stellar parallax"?
the appearance of movement of a star as a result of the Earth moving around the sun
True or False: Sir Isaac Newton discovered the idea of gravity and introduced it to the world.
False; Gravity was known before Newton (Robert Hooke preceded Newton), but he was able to build on those ideas by expressing its existence as a math equation to be used universally, between any two objects with mass.
DAILY DOUBLE:
BOTH -- write down the equation for gravity!!
F = Gm1m2/r2
For every action, there is an equal and opposite reaction. In conclusion, the force of gravity depends on the masses of both objects.