Final Flashcards
(11 cards)
Principles of General Relativity (2)
1) Principle of General Covariance - Laws of physics are the same in all reference frames regardless of how those reference frames are moving in relative to each other.
reference frames = point of view
2) Principle of Equivalence - the effects due to acceleration & the effects due to gravity are the same (see elevator examples)
Confirming Evidence of General Relativity
1) Mercury’s Orbit - Mercury’s perihelion (the point of mercury’s orbit closest to sun) drifting/migrating. Newtonian equations works ok to make predictions, but using General Relativity equations works perfectly
2) Light from stars should be red-shifted -> light should appear more red than blue
- observations match well w/ predictions
3) Gravitational forces impact space time -> in the presence of a strong gravitational field, time slows -> time dilation, how much length should be contracted, how much time should be dilated
4) General Relativity predicts a curvatire of space time.
- similar to magnetic field lines, you can’t interact with spacetime like you would with a ball or something more tangible
- conceive of spacetime as a linear dimension continuum, with 1D=time, 3D=space
- Geodesic -> an object moves because it’s progressing along a geodesic
5) GR predicts presence of gravitational waves when large objects are accelerated - > success of LIGO experiment confirms presence of waves
6) Starlight bending as it passes close to sun, Einstein’s 1916 paper predicted this, did not have evidence until observations from 1919 solar eclipse, which agreed with Einstein’s predictions
General Relativity and Gravity
in GR, bodies not under the influence of any forces->they move along geodesic
- bodies arent moving directly because of attractive forces on them
- mars doesn’t move in an elliptical orbit because of anything having to do with an attractive force ->moves in a straight line along curved space time aka a geodesic
Quantum Facts, theories, interpretation
Facts - outcomes of experiments involving quantum entities like protons and electrons; surprising but not controversial
Theory - mathematics of the theory itself, used to predict & explain facts. Very successful in terms of predictions
Interpretation - this is where debate is
Experiments with Quantum entities
a) basic 2 slit experiment - shoot electrons at a barrier with 2 slits, record results of experiment on photographic paper = clear wave effect aka interference pattern
b) repeat a with 1 slit open at a time = clear particle effect
c) experiment 3: same as #1, but include passive detectors to monitor the slits so we can “see” what’s going on at each slit = particle effect
d) experiment 4: enormously slow down the rate of electron-firing -> get particle hits but over time seem to generate an interference pattern
e) experiment 5: beam splitter with detectors off = wave effect
f) like experiment 5 with detectors on = particle effect
Copenhagen/Standard Interpretation of Schrodinger’s Cat/
-QT is complete except for 1 thing, the ‘projection postulate’ and the math behind it
1) Mild measurement Dependent Reality:
- narrow view of quantum entity
- -broad view of measuring devices
2) Moderate Measurement Dependent Reality
- broad view of quantum entity ->anything can exhibit the behavior of a quantum entity, not just photons & electrons
-broad view of measuring devices
3) Radical Measurement Dependent Reality
- broad view of quantum entity
- narrow view of measuring device -> only human consciousness counts
Hidden Variable Interpretation
Quantum Theory is incomplete, needs to be amended significantly, not just addition of projection postulate is necessary
Einstein’s Realism - QT leaving something out -> “elements of reality”
-mathematics are incomplete as is
Many Worlds/Multiverse Theory
-Solves the problem of the collapse of the wave function in that there is no collapse
–we inhabit all infinite # of states that all exist in superposition with respect to each other & all states are real
EPR thought experiment
-by Einstein, Podolsky, Rosen
EPR SUGGESTS LOCALITY
- Polarization = attribute of photons
- generate photons in twin state and measure polarization as “up” or “down”
- nothing implied about what is the polarization prior to measurement
Claim #1: Photons have definite polarization prior to being detected (if EPR can convince us of #1 being correct, they have a powerful argument against QT)
Claim #2: QT (the math) doesn’t represent the photons as having any definite polarization prior to being detected, therefore QT is an incomplete theory
Argument in favor of claim #1:
- need to understand ‘locality assumption’
- Locality assumption says that what happens at one location can’t influence what happens at another location unless there’s some sort of connection between the two locations
-Either locality is false or QT is incomplete. Locality is very reasonable & no one will give it up so QT is incomplete
Bell’s Theorem (coke machine)
2 machines, A & B, with dials LMR which produces diet soda (D) or 7-Up (U)
Scenario 1:
A: M
B: M
both produce identical sodas but 50% is U, 50% is M, but identical meaning when A produces U, B produces U.
Scenario: 2
A:L
B:M
25% difference in out put of machines when dials set this way
Scenario #3
A: M
B: R
-25% difference
Scenario #4
A: L
B: R
what we predict is 50% difference in outcome
QT doesn’t agree with #4, QT predicts 75% difference in outcome
Aspect’s Theory
Suggests locality is not correct
