Physical Universe Unit 2 – Flashcards
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Age of The Universe
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14 billion years
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Age of The Galaxy
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10 billion years
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Age of The Earth
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4.7 billion years
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Age of The Solar System
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4.7 billion years
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Lunar Calendar
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months are created to match cycles of Moon, all cultures start with this, not connected to seasons
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Solar Calendar
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consistently ties to equinoxes, solstices, and seasons
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Lunisolar Calendar
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months tied to the moon, aligned with seasons
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A.U.
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average distance between sun and earth. measures distances within our solar system
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Lightyear
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distance that light travels in one year. use it to measure distances outside our own solar system
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Winter Solstice
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sun is at southernmost point in sky. our hemisphere is tilted directly away from sun
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Summer Solstice
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sun is at northernmost point in sky. our hemisphere is tilted directly toward the sun
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Spring/Fall Equinox
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sun shines directly down the equator
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Solar Day
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the time it takes for the sun to return to the same position above you in the sky
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Sidereal Day
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time it takes for the Earth to do a 360 degree spin
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Synodic Month
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time it takes for Moon to complete its cycle of phases
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Sidereal Month
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time it takes for Moon to complete one orbit around Earth
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what causes cycles?
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moon reflects light from sun, half of moon is always lit but the angle from the earth shows only part of lit and dark sides.
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if a full moon occurs when the moon is on one side of Earth and the Sun is on the other side, then how come we don't always see a lunar eclipse when there's a full moon?
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Because the moon and the earth travel around the earth in different orbital patterns.
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what are two reasons that the Earth's tilt leads to seasonal temperature changes?
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because when the earth tilts, more of one half of the earth is getting more direct sunlight leading to a warmer climate. Also this creates more hours of daylight.
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copernicus proposes that the universe is heliocentric. how does he explain retrograde motion with this model?
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He says that Mars appears to go backwards when Earth laps mars on it's revolution around the sun.
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why didn't copernicus run into trouble with the catholic church?
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wrote "On the Revolutions" in latin, but didn't publish until he was on his deathbed, and added a dedication to the pope in his prologue
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what is significant about Brahe?
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Collected data on Mars' retrograde motion, and believed the universe was geocentric
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what are kepler's three laws of planetary motion?
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1. Planets orbit the sun in elliptical orbits 2. Planets sweep out equal area at equal time 3. Inner planets travel faster than outer planets
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compare and contrast the models of ptolemy, copernicus, and kepler (we have a w/s about this)
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Copernicus and Kepler had heliocentric models while Ptolemy had a geocentric model. Copernicus said that things revolved around the sun in perfect circles while Kepler discovered that planets revolve around the sun in ellipses.
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what are galileo's three major contributions to science (use specific examples of each)
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i. The study of motion: found that heavy things and light things fall at the same rate (tower of pizza?. ii. Used lots of experiments to do science. (Changed the way science is done) iii. Cosmology- (moon, sun, jupiter moons, venus's phases) (SEE NOTES!)
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what are the four new discoveries galileo made when studying the night sky?
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i. Moon- discovered "mountains, valleys, and seas" on the moon. IMPORTANCE: heavens are not perfect. Is there a pope on the moon??? Aristotle was not right that the heavens were perfect and orderly. ii. Saw sunspots on the sun. IMPORTANCE: the sun is not a perfect sphere like Aristotle thought. It is actually chaotic. iii. Discovered four moons around Jupiter. IMPORTANCE: Goes against religion (Catholicism) because they said the heavens can't have two centers. Also if Jupiter has moons is it just like Earth??? Is Earth not special??? :( iiii. He saw the phases of Venus. IMPORTANCE: Saw some big crescents and even some gibbosus. This does not match up with Ptolemy's geocentric model of the universe.
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why did galileo run into trouble with the catholic church?
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He ran into trouble because he went against the geocentric model. (The belief of the Catholic church.)
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how was galileo's work different from copernicus so that galileo got in trouble but copernicus did not? (give 5 reasons)
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i. Copernicus published his book on his deathbed ii. Copernicus did not say the heliocentrism was for sure true. Just said that it worked out mathematically. iii. The inquisition told Galileo to abandon his ideas of heliocentrism but he did not and published a book where two characters argue about each model of the universe. The geocentric character is named Simplicus to emphasize that the heliocentric model is correct. iiii. The Catholic church was worried that Galileo would gain supporters because of his ideas but they were not worried about Copernicus iiii. Copernicus wrote his book in latin while Galileo wrote it for everyone to read
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how did galileo combine his faith in the bible with his views about science?
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Says that not all interpretations of the bible are inspired by God. The bible is vague and does not really describe nature. Just because of his findings does not mean that the Bible is wrong.
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what are newton's 3 laws of motion?
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i. An object in motion stays in motion and an object at rest stays at rest unless acted upon by an outside force ii. a= f/m iii. For every force there is an equal and opposite return force.
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which of newton's three laws explained why heavy things do not fall faster than light things?
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The second law (a= f/m)
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what is the law of universal gravitation?
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F=G(m1xm2/d^2)
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what did newton unify?
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Apples and the moon. Both fall by gravity. However, moon falls with sideways velocity.
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what new ideas or new insights did we get as a result of this important unification?
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i. Why planets obey Keplers laws ii. why/how the moon orbits iii. Satellites (Why they stay in orbit) iiii. We can know the heavens (rules are the same) v. We now know why the oceans have tides
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how do satellites orbit?
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They get sent out at a very high sideways speed to let them break the barrier between earth and space. Once they are in space, they just keep "falling" around the earth in an orbital pattern.
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why do satellites speed up as they approach the planet and slow down as they go farther away? (in other words, why is kepler's 2nd law true)
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Like in projectile motion, when an object gets closer to the center of the gravity is speeds up, but when it is farther away it is like the top of a projectile where it appears to not be moving
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what is the difference between weight and mass?
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weight: amount of gravity acting upon an object mass: how much space something takes up
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what is the difference between true weightlessness and apparent weightlessness?
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apparent: when an astronaut appears to be weightless in a shuttle, because they are orbiting the earth at the same speed as the shuttle; both falling at same rate true: this is only found in deep space
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how does the moon cause the earth's tides?
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because its gravitational pull on the earth pulls on the water harder on one side than the other
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why is it impossible for the moon to cause tidal stretching on the fluid in your body?
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because the fluid is your body isn't massive enough to be able to be stretched. Only things like oceans and rivers could be tidally stretched.
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what are all of the six themes individually about?
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Humanity's place in the cosmos: all about where different people think the earth is in relation to the universe. Is the universe knowable?: are we capable of understanding our universe? or are we somehow prohibited from seeing the true nature of the world around us. Discrete vs Continuous: are different things able to be broken down into a smallest thing or not. How to do science: shows how different scientists and philosophers did science in a way. Unification: when two things that are thought to be separate are in fact shown to be connected and this connection leads to insights. Clockwork Universe/Determinism: talks about the universe being a clock filled with gears and once we figure out all the gears in the clock we will understand the universe. If we understand all of this, is our future already predetermined?
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give an example of how isaac newton is relevant to each theme
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Humanity's place in the cosmos: believed that gravity existed in earth and space. Is the universe knowable?: believed that gravity existed in earth and space. He believed the universe was knowable. Discrete vs Continuous: proposed light was discrete being made up of corpuscles How to do science: he used thought experiments to conceptualize gravity Unification: apple and the moon concept. Gravity being present on both moon and earth. Clockwork universe/Determinism: came from his ideas dealing with a knowable universe with gravity
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Ptolemy vs. Kepler
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Compare: Worked off of other scientists findings. Ptolemy based his work off of Aristotle's findings, while Kepler based his work off of Brahe's data he collected about Mars. Contrast: Ptolemy believed we were in a geocentric model, while Kepler believed we were a heliocentric model. Ptolemy used epicycles to explain retrograde motion while Kepler used his third law of planetary motion (inner planets move faster than outer planets).
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Kepler vs. Galileo (both favored heliocentrism, but approached it with different evidence)
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Kepler: used Mars data and observing where things were, then tried many different models until he found the most accurate Galileo: used observations like the phases of Venus and moons orbiting around Jupiter to explain why Earth can orbit Sun
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Advantages of Copernicus' cosmology over Aristotle's and vice versa
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Aristotle's model was very easy to understand and was widely accepted by the common folk because of this. Everything suddenly made sense to the public, although it is completely wrong. Copernicus' model was actually mathematically calculated to discover the facts and was correct, but everything was written in Latin so only other scholars could truly understand the evidence.
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Differences between Kepler and Copernicus' model of the universe
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They are both similar in that they believed in the heliocentric model, although Copernicus believed everything orbited in perfect circles (which ended up being incorrect). Kepler explained the solar system through elliptical orbits, which challenged the thoughts of Copernicus' model. Kepler had his 3 laws of planetary motion to back up his model also.
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How does Ptolemy's geocentric model explain retrograde motion and how does the heliocentric model explain retrograde motion?
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Ptolemy explained retrograde motion with epicycles. The heliocentric model explains retrograde motion with Kepler's laws of planetary motion, which shows that some planets orbit at different speeds and speed up when closer to the sun.
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If there were 2 kinds of scientists, Pythagoreans and non-Pythagoreans, in which side do each belong? (aristotle, copernicus, galileo, kepler, newton, ptolemy)
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All are "Pythagoreans" besides Aristotle, who didn't find his work mathematically
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Why is Ptolemy's work deterministic?
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Ptolemy's work was deterministic because he used math formulas to describe the rules of planetary motion. It showed that the universe is predictable.
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Explain the Allegory of The Cave and explain the metaphor for clockwork universe. What would Plato say about the clockwork universe metaphor?
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Allegory of the cave: prisoners in a cave only understand the shadows of things that pass by. Someone escapes, sees world, no one follows or believes. Only clear rational thinking can lead you to truth. Clockwork universe: Universe is a perfect mechanical clock that runs with the laws of physics. Everything is predictable. Plato wouldn't believe in the clockwork universe because he believes you can truly never trust what you see or what is happening.
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Which ancient scientist is most like or unlike Newton and why?
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Aristotle is most like Newton because they both had ideas that they never really tested out. Like Newtons "thought experiment" with gravity and Aristotle's idea of aether. Plato is most unlike him because he said you can't trust your senses but Newton always trusted his senses because of his lack of experimentation.
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Occams Razor
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States that the simpler argument is most likely the right one
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Thales
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Got science started by saying "the universe is knowable."
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Democritus
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Matter is discrete. Or matter is made up of tiny building blocks called atoms.
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Aristarchus
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heliocentricity
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Eratosthenes
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measured the size of the earth
