Test 1 Flashcards
The start of the Universe’s expansion is commonly called ___ ___ ____.
The Big Bang
What is our cosmic address?
Earth, solar system, Milky Way Galaxy, local group, local supercluster, Universe
The farther away we look in the ____, the farther back we look in ____.
distance; time
Lightyears
The distance light can travel in one year
According to the Voyage Model, if the Sun was a grapefruit, the Earth would be a ____ ______. Jupiter would be a _____.
pen’s ballpoint; marble
The nearest star to the Sun is __ light years away.
4
If a light year is 1 mm, the Milky Way is the length of a _____ _____.
football field
If the time span between the Big Bang and now were a calendar, when would humans be?
Last 30 seconds of December 31
Earth’s daily rotation is…
how it spins on its axis
Earth’s orbit around the Sun is a _____.
revolution
Earth’s average orbital distance is equal to
1 au (astronomical unit)
1 au =
150 million km
Earth’s orbital path defines a flat plane called an ____ ____.
ecliptic plane
Does the solar system move in relation to other stars?
Yes
How fast does the solar system move in relation to other stars?
70,000 km per hour
40,000 mph
Virtually, every galaxy outside the Local Group is moving ____ us.
away from
Who developed the first scientific model for astronomy?
Ancient Greeks
All scientific models are subject to being _____.
disproved
Always change the ____ rather than the ____.
model; data
A scientific model requires what 3 things?
Geometry, Physics, Aesthetics
What are the 5 steps of a scientific model?
“Real World” -> observe nature -> Model (geometry, physics, aesthetics) -> comparative observations -> revise model to match observations
Does a scientific model require accuracy to qualify as a model?
No
What type of universe did Ptolemy believe in?
Ptolemaic System: geocentric
Did the Ptolemaic System qualify as a scientific model? Was it accurate?
Yes; No
uniform circular motion
Move in a circle at a non-varying speed
Aristotelian Physics
The natural motion of all earthy materials is to fall towards the center of the universe (Earth)
What are the four earthy materials in Aristotelian Physics?
Earth, air, fire, water
According to Aristotelian Physics, what are the planets/heavenly bodies made of?
The 5th material, quintessence
Greeks were obsessed with perfect _____ and _____.
circles; spheres
What three things supported the Ptolemaic System?
uniform circular motion, Aristotelian Physics, Greek love of perfect circles and spheres
Greeks believed the heavenly bodies had no ____.
blemishes
Copernicus proposed a ____ model for the universe.
heliocentric
What did Copernicus believe orbited the earth?
Just the moon
What was the Copernican System’s primary motivation?
Aesthetics
Was the Copernican System more accurate than the Ptolemaic System? Why or why not?
No. Held flawed belief in uniform circular motion.
Did the Copernican System qualify as a scientific model?
No, there was no physics aspect.
What was the geometry aspect of the Copernican System?
uniform circular motion
Was the Copernican System a better or worse scientific model than the Ptolemaic System?
worse
What did Tycho Brahe contribute to astronomy?
astonishingly accurate naked-eye observations
How were Tycho’s observations so accurate?
he had a giant angle-measurer
How accurate were Tycho’s observations?
within an arcminute
What is an arcminute?
1/60 of a degree
Did Tycho side with Ptolemy or Copernicus?
Ptolemy
Tycho’s data allowed people to _______________.
test the Ptolemaic and Copernican models
What did Galileo contribute to astronomy?
he invented a stronger telescope
Galileo began the process of finding _____ to satisfy the Copernican System.
physics
What made Kepler a better scientist than those before him?
He tossed out ideas if they didn’t fit the model or agree with the data.
Kepler tossed out ideas if they didn’t fit the ____ or agree with the ____.
model; data
Kepler was _____’s apprentice.
Tycho
Did Kepler like the Ptolemaic or Copernican System?
Copernican
What did Kepler discover?
elliptical orbits
Kepler changed the ____ to fit the ____.
model; data
What is an example of Kepler changing the model to fit the data?
He substituted an ellipse for a circle in regards to orbits.
What is Kepler’s first Law of Planetary Motion?
Planets orbit the Sun in elliptical orbits with the sun at one focus.
What is Kepler’s second Law of Planetary Motion?
As a planet orbits the Sun, its distance from the Sun changes. If it’s closer to the Sun, it moves faster. If it’s farther from the Sun, it moves slower.
According to Kepler’s second law, planets mover faster when they are _____ ____ the Sun.
closer to
According to Kepler’s second law, planets mover slower when they are _____ ____ the Sun.
farther from
What is Kepler’s third Law of Planetary Motion?
There is a mathematical relation between a planet’s period (time it takes to orbit Sun) and its distance from the Sun.
p^2 = K * a^3
More distant planets orbit the Sun at slower average speeds, obeying the precise mathematical relationship
p^2 = a^3
In p^2 = K * a^3, what is p?
p = period
In p^2 = K * a^3, what is K?
K involves the mass of the Sun
with right units, K = 1, rendering it unnecessary in the equation
p^2 = a^3
In p^2 = K * a^3, what is a?
a = distance between the Sun and the planet
measured in au (astronomical units)
p^2 = K * a^3 can be used to determine the ____ of stars.
mass
Kepler’s third law is the only way we have of measuring the ____ of faraway space objects.
mass
How did Kepler’s model involve physics?
magnetic force between Sun and planets (incorrect)
How did Kepler’s model involve geometry?
ellipses
Isaac Newton built on _____’s model and _____’s data.
Kepler; Galileo
What does Newtonian Physics include?
Three Laws of Motion and Law of Gravity
Newton’s telescopes used ____ instead of lenses.
mirrors
Newton invented what mathematical discipline?
calculus
Newton’s Three Laws of Motion ____ (prove/disprove) Kepler’s Laws.
prove
Newton’s Laws explain the movement of ____.
planets or heavenly bodies
What is Newton’s first law?
Inertia. Every body continues in its state of rest or uniform motion in a straight line unless an external force acts. An object at rest tends to stay at rest, while an object in motion tends to stay in motion.
Velocity includes ____ while speed does not.
direction
acceleration
any change in velocity (speeding up, slowing down, changing direction)
A negative acceleration is _____ ____.
slowing down
A positive acceleration is ____ ____.
speeding up
G-force happens when you’re in something accelerating ____.
positively
Inertia happens when you’re in something accelerating ____.
negatively
What is the difference between G-force and inertia?
G-force: positive acceleration
Inertia: negative acceleration
In order to accelerate an object, you must apply __ _____ ____.
an external force
Applying a perpendicular external force to an object changes ____.
velocity
Applying a parallel external force to an object changes ____.
speed
To change an object’s velocity, you must apply a _____ _____ force.
perpendicular external
To change an object’s speed, you must apply a _____ _____ force.
parallel external
When applying the same force, more massive objects accelerate ____ and less massive objects accelerate ____.
less; more
What is Newton’s second law?
force = m*a force = mass * acceleration
The rate of change of momentum of a body is proportional to ____ ______ ______.
the applied force
The rate of change of momentum of a body takes place in the direction ___ _____ _____.
the forces takes
What is Newton’s third law?
To every action, there is an equal and opposite reaction.
What is the reaction of Earth’s gravity pulling you down toward its center?
you pull the Earth up with the same amount of force
What is an example of an action/reaction pair?
you/Earth
Earth/Sun
action = ?
action = change of momentum * distance over which momentum is changed
Earth pulls you down and you pull Earth up with a force equal to ____ ____.
your weight
Explain the fuel/rocket action/reaction pair.
The built up fuel pressure pushes out back of rocket, thrusting rocket up.
What is Newton’s Law of Universal Gravitation?
There is a force of gravitation between any 2 objects in the universe. More massive objects have a greater gravitational force.
Force = G * [Mass(1) * Mass(2)] / (Distance)^2
_____ is also a factor in Newton’s Law of Universal Gravitation.
Distance
radius
the distance to the center
Give an example of distance being a factor in Newton’s Law of Universal Gravitation.
You -> Earth
Earth -> Sun
Where should you measure the distance between two objects from?
their centers
ex.: Earth’s center -> your bellybutton
In Force = G * [Mass(1) * Mass(2)] / (Distance)^2, what is G?
gravitational constant
In Force = G * [Mass(1) * Mass(2)] / (Distance)^2, what is the distance?
between the two objects’ centers
Why don’t you fall toward other objects if there’s a gravitational force between you?
The gravitational force between you and the Earth is greater, because Earth has a greater mass than any object on it. Earth pulls you down.
If the distance between two objects doubles, there’s ____ the force.
1/4
If the distance between two objects triples, there’s ____ the force.
1/9
If the distance between two objects is 10 times, there’s ____ the force.
1/100
If an object weighs 100 N, and its distance from Earth doubles, what does it weigh now?
25 N (Newts)
The moon is basically ____.
falling
The more massive object has more force acting on it, thus it takes ___ force to accelerate it.
more
Two objects orbiting the same object will have ___ orbital periods/speed/etc.
equal
In general, for anything to move in a circular path, you have to have an inward force that’s constantly applied for a change in direction. What is this force?
centripetal force
centripetal force
a force that acts on a body moving in a circular path and is directed toward the center around which the body is moving
When the moon orbits Earth, ____ applies the centripetal force.
gravity
If centripetal force suddenly stops, the object will…
go in a straight line (Newton’s first law, inertia)
Do things fall on the moon?
yes
What fraction do objects weigh on the moon compared to Earth?
1/6
While falling, an object is ____.
weightless
What two modifications have been made to Newton’s laws?
Quantum Mechanics (atoms do not obey Newton's laws) Einstein's Relativity
What is the Law of Conservation of Energy?
total amount of energy in the universe always remains the same
How does the Law of Conservation of Energy work?
different types of energy (gravitational, motion, etc) convert into one another
Does mass affect orbital periods?
No
What affects orbital periods?
orbital distance
eccentricity
amount an ellipse is stretched compared to a circle; circles have zero eccentricity
Why can we use Kepler’s third law to calculate a planet’s average orbital speed?
The law relates a planet’s orbital distance to its orbital time (period).
How did Galileo answer the aesthetic objection to a heliocentric system?
Using his telescope, he proved the existence of sun spots and mountains & valleys on the moon.
stellar parallax
apparent shifting of an object against a background; parallax depends on distance, nearer objects experience greater parallax than more distant objects
What is Occam’s Razor?
the idea that scientists prefer the simpler or more aesthetically pleasing of two otherwise equal models
