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68 Cards in this Set

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Epicycle
a small circle the center of which moves around a point on the circumference of a
larger one
Eccentric
circle around a point that is off center where epicycles revolve.
The center of the epicycle moves around on a larger circle which is called an eccentric
Equant
circle around a point that is off center where epicycles revolve.
Homocentric Spheres
Think of this as 2 crystal spheres where the smaller one is inside the larger one but is on the same axis. If we counter rotate the outer sphere relative to the inner one then it makes a dot on the inner sphere’s equator looked fixed. However if the axis is offset when counter rotation occurs then the dot will exhibit a figure 8 motion. If this figure 8 is superimposed on the two sphere model then it could explain retrograde motion.
Eudoxus
was first to propose the homocentric spheres concept.
Heliocentric
Sun-centered. Heliocentric theories placed the sun at the center of the universe.
Retrograde Motion
is motion in the direction opposite to the movement of something else. This was observed when wandering planets seemed to slow down then go backwards in the night sky and then resume normal motion with regards to the sphere of the stars.
Diurnal Motion
An astronomical term referring to the apparent daily motion of stars around the Earth, or more precisely around the two celestial poles.
Geocentric
Earth-centered. Geocentric theories placed the Earth at the center of the universe.
Two-Sphere Model
is a geocentric model that divides the cosmos into two regions. A spherical Earth, central and motionless (sublunar realm) and a spherical heavenly realm centered on the Earth, which may contain multiple rotating spheres made of aether. This was used to explain the suns movement/ location in so that it rotates around the outside sphere.
Aristarchus
Greek astronomer that presented the first known heliocentric model of the universe.
Anaximander
a presocratic philosopher; said that the basic “stuff” of the universe is something indefinite/unlimited called “apeiron”.
Summer Solstice
When the axis of the earth tilts toward the sun we have summer in the northern hemisphere around June 20th. At this point the sun is at its highest point in the sky at noon.
Vernal/Autumnal Equinoxes
occurs twice a year, when the tilt of the Earth’s's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the
Earth's equator. vernal=spring autumnal=fall
Antiperistasis
An attempt to explain why an object when thrown continues to travel straight and not immediately fall down to the ground as earth was thought to behave. Air moves from the front of the object to the back of it and as a result pushes the object.
Principle of Sufficient Reason
States that anything that happens does so for a reason: no state of affairs can obtain, and no statement can be true unless there is sufficient reason why it should not be otherwise. Used by Leibniz when arguing with Newton.
Natural Motions
the falling of objects and substances have a natural place or level such as air above, water below and they proceed in the most direct way, along straight vertical paths to their natural places. Air and fire go straight up to the heavens away from the center of the cosmos. Water and Earth fall straight down to the center of the Earth. Aether moves in circles.
Violent Motions
any motion other than the natural motions explained above. For example picking up a rock involves violent motion.
Impetus
“Power to move.” Thought to gradually dissipate over time, idea was used in Aristotelian physics to explain the continued motion of an object after contact is lost with the original projector.
Heraclides of Pontus
best known for proposing the theory that the earth revolves on an axis from west to east once every 24 hours, which explains the motion of the stars.
Plenum
A space completely filled with matter
Horror Vacui
theory first proposed Aristotle that stated that nature abhors a vacuum and therefore would be trying to suck in gas or liquid to fill an empty space if there is one.
Giordano Bruno
His cosmological theories went beyond the Copernican model in proposing the sun was essentially a star, and moreover that the universe contained an infinite number of
inhabited worlds populated by other beings. He was burned at the stake for heresy. And helped Copernican model be more acceptable to religious people because a very large, possible infinite, universe would reflect an infinite god.
Neoplatonism
“Christianized” version of Plato’s philosophy concerning a wide variety of objectively existing, nonphysical, eternal “forms”; he focused on truth and beauty, but above all
Good (symbolized as the sun-- the source of life) and Good is truth and knowledge. Neoplatonists replace Good with the Christian God, so that He was the highest form.
Stellar Parallax
a parallax is the apparent shift in position of stellar objects due to your motion
Tycho Brahe
(1546-1601) blends copernican and ptolemaic astronomical systems; was a respected astronomer known for accurately collecting empirical data.
Tychonic model
blend ptolemaic and copernican models-- the earth is the center of the universe, and the moon and sun revolve around the earth; the planets revolve around the sun.
Kepler
1571-1630 finally developed a system that was simpler, but accurate in explanation and prediction; he worked for Tycho Brahe and was highly influenced by him, especially in collecting data; broke perfect circle and uniform motion laws; designed elliptical orbits with varying speeds.
Kepler’s Laws: 1st law of planetary motion
planets orbit the sun in elliptical orbits, with the sun
occupying 1 of the foci in the ellipse
2nd Law of Planetary Motion:
For any equal time period, the movement of the planet covers an equal area-- in an ellipse, that kind of movement results in varying speeds
Kepler's Laws: 3rd Law of Planetary Motion
The ratio of a planet’s period (T) squared to its semi major axis (a) cubed is constant. i.e (T1/T2)^2 = (a1/a2)^3 where T is the planet’s period and a is its semi major axis
Galileo
(1564-1642) Italian physicist, mathematician, astronomer and philosopher who was known for his championing of heliocentrism. Galileo stood correct on many of his observations but was wrong in denying the moon’s cause of the tides and Kepler’s belief in the elliptical nature of planetary orbits.
Law of Inertia
An object in motion remains in motion in a straight line, and an object at rest remains at rest unless acted upon by an outside force.
Isaac Newton
(1642-1727) English physicist, mathematician, astronomer, etc. who is arguably the most prominent scientist who ever lived. Newton lays the foundation for classical mechanics, the law of universal gravitation, the three laws of motion and most notably his development of calculus. Newton is responsible for removing the final doubts of heliocentrism.
Relationism
The idea that space exists only as a relation between objects, and has no resistance apart from the existence of these objects. Motion exists only as a relation between these objects.
Substantivalism (about space)
Opposing relationism, substantivalism states that space is, in fact, a real entity and the nature of our reality can not solely be described using talk regarding relations between objects. One is forced to define reference frames in space to understand the dynamics of our universe.
Identity of Indistinguishables
The prospect of a particle being indistinguishable arises from the uncertainty of its position as well as its lack of uniqueness in relation to identical particles surrounding it.

In this sense, you can not paint two electrons in close proximity as red and blue and call the Electron A and Electron B because you can’t say which electron is which; after all, even God doesn’t know which electron is which. In this sense, the two particles are indistinguishable.
Cosmology
The study of the nature of the universe as a whole. Cosmologists seek to understand the origin, evolution, structure and fate of the Universe as we as its governing physical laws.
Interference Pattern
the pattern created by different waves interacting--waves can combine
to form larger waves or cancel each other out to form a ‘valley’; the pattern would be alternating
bands of light and dark (on photographic paper). Bright fringes occur in areas of constructive interference [waves in phase with one another] and dark fringes occur in areas of destructive interference [waves 180 degrees out of phase]).
Ptolemy
(90-168AD) Ptolemy was a Greek-Roman citizen of Egypt whose noteworthy contribution to astronomy is the Ptolemaic Model in which planets travel in epicycles, the centers of which orbit in uniform motion around the Earth.
Twin Paradox
If one of a set of twins travels near the speed of light to some star 15 light-years away and the other twin remains on Earth, when the astronaut twin returns, she will be nearly as young as when she left, whereas her twin will have aged 30 years.
Two-slit experiment
When a monochromatic source of light travels through two slits separated a given distance from one another, the two emerging light beams will converge upon the wall behind the grating. Depending on whether the rays are in phase or out of phase, they will either constructively interfere to form bright fringes or destructively interfere to form dark fringes. This is known as an interference pattern and extends to beams of particles (electron beams) as well as traditional light (photons).
EPR ‘paradox’
(This is my best attempt at explaining the paradox -- I don’t completely understand it myself) Paradox against QM posited by Albert Einstein, Boris Podolsky and
Nathan Rosen. If a particle is coupled to another particle (entaglement) and both particles arrive at detectors located in two opposite directions from the particle-source, their positions and momentum can be thought of as correlated. Based on Heisenberg’s Uncertainty principle, if the position of one particle is well known, the momentum is uncertain, but since the two particles are entangled, the second particle’s momentum must also retain an equal sense of uncertainty. The EPR paper states that the particles need to have hidden parameters (hidden variables) to explain why the second particle knows that it should have uncertainty in momentum. Since there is no room for hidden parameters in the formalism of QM, the whole theory must be incomplete.
Bell’s Theorem
No physical theory of local hidden variables can reproduce all of the predictions of quantum mechanics. (A local hidden variable theory is one in which distant events are assumed to have no instantaneous (or at least faster-than-light) effect on local ones.)
Hidden-Variable Theory
Historically, in physics, hidden variable theories were espoused by some physicists who argued that quantum mechanics is incomplete. These theories argue against the orthodox interpretation of quantum mechanics, which is the Copenhagen Interpretation. Albert Einstein, the most famous proponent of hidden variables, famously insisted that, "I am convinced God does not play dice", but whether he objected to the statistical nature of quantum mechanics is disputed.
Copenhagen Interpretation
the standard interpretation of quantum theory, that it reflects reality, and the fact that we can’t know what the outcome of a quantum event will be before measurement takes place (before the ‘wave collapse’) is not because we can’t know, but because quantum entities lack definite attributes before the measurement takes place.
Black-Body Problem
The black-body is an idealized physical entity that absorbs all
electromagnetic radiation incident upon it.
Instrumentalism
an adequate theory is one that predicts and explains; however, whether that theory reflects or models reality is not important.
Polarizer ‘Paradox’
polarization measurements are actually changing the state of photons.
Photoelectric Effect
When light is shone on metal, the surface may become positively charged. This is because electrons gain energy from the light waves, and are able to leave the metal's surface.
Determinism/ Indeterminism
classical physics is deterministic; the physical state of the world is determined by a description of all objects’ mass/speed/location...so in principle, if you know state
at time1, you can figure out what the state will be at time-n.
Atomic Spectra
When gases are heated in particular ways they emit light at selected frequencies, each has its own set of frequencies. The frequency at which a photon is emitted/absorbed corresponds to the energy between atomic levels/orbitals.
Wave Superposition
In QM, the existence of a variable (let’s say position) is determined by a probability density function which results from a superposition of all possible wave functions in the system. In a coin flip example, the resulting wave function can be thought of the wave function for heads and the wave function for tails -- in this case, the two wave functions are added together to define the underlying system.
Uncertainty Principle
It turns out that any measurement of the position of a quantum system ‘blurs’ the momentum. Any measurement of the momentum blurs the position.
Complementarity
According to Neils Bohr, we can describe the quantum world in terms of the position of things or in terms of the momenta of things. We can not meaningfully describe the quantum world in both respects at the same time. Bohr calls the two descriptions ‘complementary’ in that each captures an aspect of quantum reality, but neither captures all of quantum reality
Delayed-Choice Experiment:
If we think of a stream of photons travelling around a celestial body, the photons can go either to the left of it or to the right of it (in two dimensions). However, if we decide to detect the photon at either the right or the left of the planet, the photon’s wave function would have to collapse as either left or right at that moment in time, but this is a delayed choice since the photon should’ve had to decide left or right when it exited its initial source. (I think this is what he was going for)
Schrodinger’s Cat Experiment
A thought experiment that shows how bizarre quantum mechanics can be in reality. Place a cat in a box containing a radioactive atom and a vial of cyanide that decomposes along with the radioactive atom. Once the cyanide is released from the vial and kills the cat, the cat is neither considered dead or alive until it is observed to be dead or alive. It is essentially stuck in a state of superposition.
Measurement Problem
An electron acts like a wave if we don’t check which hole it went through; however, it acts like a particle if we do check it.
Thought Experiment
considers some hypothesis, theory or principle for the purpose of thinking through its consequences. Given the structure of the experiment, it may or may not be possible to actually perform it, and, in the case that it is possible for it to be performed, there need be no intention of any kind to actually perform the experiment in question. The common goal of a thought experiment is to explore the potential consequences of the principle in question.
Induction
even if all premises are true, it is still possible for a conclusion to be wrong; goes from specific reasoning to general.
Worldview
a system of interconnected beliefs; an intertwined, interrelated, interconnected system of beliefs.
Deduction
goes with discomfirmation reasoning; general to specific; the facts add up to a guaranteed conclusion -- true premises guarantee true conclusion
Mechanism
teleological explanation that isn’t given in terms of goals, purposes, or functions-- Why did the rock fall? gravity --it’s the opposite of teleological explanation.
Determinism
a philosophy stating that for everything that happens there are conditions such that, given them, nothing else could happen.
Quine-Duhem Thesis
beliefs are not built separately but together-- they are a body of beliefs; our beliefs then face the “tribunal of experience” together. When you test a main belief or hypothesis, there are auxiliary hypotheses being tested as well.
Popper
(1900’s) falsificationist approach; a theory is better if it withstands attempts to falsify
it rather rather than trying to confirm it; he also said the riskier the theory the more scientific it is
Falsificationism
Popper developed this theory - good scientific theories should be designed so that they can withstand verification processes-- Newton’s theory of gravitation and Einstein’s theory pass the test
Indeterminism
The concept that events are not caused by prior events. It is the opposite of determinism and related to chance.