*"How do we know that...." ^{*}*

PHYS 444 web page

Examples of original papers (mostly experimental) which discovered, confirmed,
or established some 'Physics Phacts' which we now take for granted. The list is
very selective, focusing more on gravitational, particle, and atomic physics,
and quantum mechanics.

**Classical gravity and
relativity (special and general)**:

*"How do we know that inertial mass (m*_{I}) and gravitational mass (m_{G}) are the same thing"?- 'Torsion-balance tests of the weak
equivalence principle',
T. A. Wagner, S. Schlamminger, J. H. Gundlach, and E. G. Adelberger,
Class. Quantum Grav.
**29**, 184002 (2012). - ‘MICROSCOPE Mission: First Results of a Space Test of
the Equivalence Principle’,
P. Touboul
*et al*., Phys. Rev. Lett.**119**, 231101 (2017). *"How do we know that the force in Newton's law of gravitation is proportional to 1/r*"^{2}? -- and over what distances do we know that?- 'Tests of the gravitational inverse-square
law', E. G. Adelberger,
B. R. Heckel, and A. E. Nelson, Ann. Rev. Nucl. Sci.
**53**, 77 (2003). *"How do we know that there is a gravitational red shift?"*- 'Gravitational red-shift in nuclear
resonance', R.
V. Pound and G. A. Rebka, Jr., Phys. Rev.
Lett.
**3**, 439 (1959). - 'Test of relativistic gravitation with a
space-borne hydrogen maser',
R. F. C. Vessot
*et al.*Phys. Rev. Lett.**45**, 2081 (1980). *"How do we know that the relativistic connection between kinetic energy and speed is valid?*- Does E = γmc^{2}really work?- 'Speed and kinetic energy of relativistic
electrons', W.
Bertozzi, Am. J. Phys.
**32**, 551 (1964). *"How do we know that moving clocks run slower?"*(Using real clocks!)__Theoretical prediction__*:*'Around-the world atomic clocks: Predicted relativistic time gains', J. C. Hafele and R. E. Keating, Science, Vol.**177**, No. 4044, 166-168 (1972).__Experimental verification:__'Around-the world atomic clocks: Observed relativistic time gains', J. C. Hafele and R. E. Keating, Science, Vol.**177**, No. 4044, 168-170 (1972).*"How do we know that particles experience time dilation?"*- 'Measurement of the relativistic time
dilation using μ-mesons', D. H. Frisch and J. H. Smith, Am. J. Phys.
**31**, 342 (1963). - 'Measurements of relativistic time dilitation for positive and negative muons in a
circular orbit',
J. Bailey
*et al.*, Nature**268**, 301 (1977). *"How do we know that massive objects (like the Sun) can bend light?"*- 'Gravitational deflection of light: solar
eclipse of 30 June 1973 I. Description of procedures and final results', R. A. Brune
*et al.*(Texas Mauritanian Eclipse Team), Ap. J.**81**, 452 (1976). *“What did Einstein say about gravitational waves?”*- If you can read German, the
original paper by Albert Einstein about gravitational waves is
*"How do we know that binary stars lose energy by radiating gravity waves?"*- 'A new test of general relativity:
Gravitational radiation and the binary pulsar PSR1913+16', J. H. Taylor and J. M. Weisberg, Ap. J.
**253**, 908 (1982). - The change in period of this binary pulsar because it
is losing energy to gravitational waves being radiated away was the first
indirect test of the existence of gravitational waves.
- This discovery won the Nobel Prize in Physics in 1993.
*"How do we know that gravitational radiation is produced in merger of two black holes?"*__'__Observation of gravitational waves from a binary black hole merger'__,__B.P. Abbot*et al.*(LIGO Scientific Collaboration and Virgo Collaboration) Phys Rev. Lett.**116**, 061102 (2016).- This paper describes the first
detection of gravity waves!__direct__ *“How do we know that there is no ‘preferred’ frame of reference?” – that there is no ‘luminiferous ether’?*- ‘On
the relative motion of the Earth and the luminiferous
ether’, A. A. Michelson and E. W.
Morley, Am. Jour. Sci. XXXIV (No. 203), Nov. 1887.
- This discovery won the Nobel Prize in Physics in 1907
*“How do we know that**Lorenz invariance**holds”? – at least at the level of 10*^{-17}!- ‘Laboratory test of the isotropy of light propagation
at the 10
^{-17}level’, Ch. Eisele, A. Yu. Nevsky, and S. Schiller, Phys. Rev. Lett. 103 090401 (2009) - ‘Rotating optical cavity experiment testing Lorentz
invariance at the 10
^{-17}level’, S. Herrmann, A. Senger, K. Möhle, E. V. Kovalchuk, and A. Peters, Phys. Rev. D 80, 10511 (2009) - ‘Lorentz Symmetry Violations from Matter-Gravity
Couplings with Lunar Laser Ranging’, A. Bourgoin et al., Phys.
Rev. Lett. 119, 201102 (2017).
- ‘Superconducting-Gravimeter Tests of Local Lorentz
Invariance’,
N. A. Flowers, C. Goodge, and J. D. Tasson,
Phys. Rev. Lett. 119, 201101 (2017)

**Quantum
mechanics**:

*"How do we know the value of Planck's constant, using the photoelectric effect"?*- 'A direct
photoelectric determination of Planck's "ħ" ', R. A. Millikan, Phys.
Rev.
**7,**355 (1916). *“How do we know how Schrödinger came up with his equation?”*- ‘An undulatory
theory of the mechanics of atoms and molecules’, E. Schrödinger, Phys.
Rev.
**28**, 1049 (1926). - This paper led Schrödinger
to share the Nobel Prize in Physics in
1933
with P. M. Dirac (of Dirac equation fame).
*"How do we know that the energy levels of a 'bouncing neutron' are quantized?"*- 'Quantum states
of neutrons in the Earth's gravitational field', V. N. Nesvizhevsky
*et al*., Nature,**415**, 297 (2002). *"How do we know that the phase of a neutron's wavefunction is effected by gravity?"*- 'Observation of
gravitationally induced quantum interference', B. Colella,
A. W. Overhauser, and S. A. Werner, Phys. Rev.
Lett.
**34**, 1472 (1975). *"How do we know that particles exhibit wave-like properties, e.g. diffract?"*Examples of increasingly complex systems with larger particle mass (given in atomic mass units, a.m.u.) are shown:- Electrons (5 x 10
^{-4}):__'Diffraction of electrons by a crystal of nickel' ,__C. Davisson and L. H. Germer, Phys. Rev.**30**, 705 (1927). - Neutrons (1): 'Wave-optical
experiments with very cold neutrons'
__,__R. Gahler and A. Zeilinger, Am. J. Phys.**59**, 316 (1991). - Helium atoms (4): 'Young's
double-slit experiment with atoms: A simple atom interferometer' , O. Carnal and J. Mlynek, Phys. Rev. Lett.
**66**, 2689 (1991). - Helium molecules (2 x 4 =
8): 'Nondestructive mass selection of
small van der Waals clusters', W. Schollkopf
and J. P. Toennies, Science
**266**, 1345 (1994). - Sodium atoms (23): 'An
interferometer for atoms'
__,__D. W. Keith, C. Ekstrom, Q. A. Turchette, and D. E. Pritchard, Phys. Rev. Lett.**66**, 2693 (1991). - Sodium molecules (2 x 23 =
46): 'Optics and interferometry with Na
_{2}molecules', M. S. Chapman*et al.*, Phys. Rev. Lett.**74**, 4783 (1995). - Buckeyballs (C
_{60}) molecules (60 x 12 = 720): 'Quantum interference experiments with large molecules', O. Nairz, M. Arndt, and A. Zeilinger, Am. J. Phys.**71**, 319 (2003). - Large molecules – phthalocyanine and derivatives thereof (514 and
1298): ‘Real-time single-molecule imaging of quantum
interference’, T. Juffmann
*et al*., Nature Nanotechnology,**7**, 297 (2012). *"How do we know that |ψ(x)|*^{2}really is a probability density?”- 'On the
statistical aspect of electron interference phenomena', P. G. Merli,
G. F. Missiroli, and G. Pozzi,
Am. J. Phys.
**44**, 306 (1976). - The idea that |ψ(x)|
^{2}represents a probability density was first presented by Max Born for which he shared the Nobel Prize in Physics in 1954. *"How do we know that the Pauli principle works?"*- 'Experimental
limit on a small violation of the Pauli principle', E. Ramberg
and G. A. Snow, Phys. Lett. B
**238**, 438 (1990). - W. Pauli won the Nobel Prize in Physics in
1945
for the ‘discovery’ of the exclusion principle.
*"How do we know that the electromagnetic potential can have an effect on the quantum phase of a particle, even in a region where there are no EM fields?"*__Theoretical prediction__: 'Significance of electromagnetic potentials in the quantum theory', Y. Aharonov and D. Bohm, Phys. Rev.**115**, 485 (1959).- Note
that David Bohm was a former Penn State undergraduate! He was inducted
into the PSU ΣΠΣ chapter in 1929!
__Experimental verification__: 'Shift of an electron interference pattern by enclosed magnetic flux', R. G. Chambers, Phys. Rev. Lett.**5**, 3 (1960).*"How do we know that spinor wavefunctions (for spin ½ particles) change sign under a 2π rotation?"*__Theory prediction__: 'Observability of the sign change of spinors under 2π rotation', Y. Aharonov and L. Susskind, Phys Rev.**158**, 1237 (1967).__Theory prediction__: 'Spin precession during interferometry of fermions and the phase factor associated with rotations through 2π radians', H. Bernstein, Phys. Rev. Lett.**18**, 1102 (1967).__Experimental verification__: 'Verification of coherent spinor rotation of fermions', H. Rauch, A. Zeilinger, G. Badurek, A. Wilfing, W. Bauspiess, and U. Bonse, Phys. Lett.**54A**, 425 (1975). This experiment used slow neutrons.*"How do we know that Quantum Electro*- Allowing theory and experiment to agree to 12 decimal places, at least for a very few special physical quantities?**d**ynamics (QED) works so well?- 'Tenth-order QED
lepton anomalous magnetic moment: Eighth-order vertices containing a
second-order vacuum polarization', T. Aoyama, M. Hayakawa, T.
Kinoshita, and M. Nio, Phys. Rev. D
**85**, 033007 (2012) - This
article contains numerous references to earlier theoretical and
experimental papers. This field has a very rich history of increasing
precision of both theoretical predictions and experimental data.

**Particle
physics:**

*"How do we know that the proton is 'stable'? or at least what limits there are on its lifetime?"*- 'Search for
proton decay via p → e
^{+}π^{o}and p → μ^{+}π^{0}in a large water Cherenkov detector' H. Nishino*et al*. (Super-Kamiokande Collaboration), Phys. Rev. Lett.**102**, 141801 (2009). *"How do we know that the electron is 'stable'? or at least what limits there are on its lifetime?"*- 'Test of electric charge conservation
with Borexino' M. Agostini
*et al*. (Borexino Collaboration), Phys. Rev. Lett.**115**, 231802 (2015). *“How do we know the muon (μ) or mu-meson exists?”*- ‘Note on the nature of cosmic-ray particles’, S. H. Neddermeyer and C. D. Anderson, Phys. Rev.
**51**, 884 (1937). - ‘New evidence for the existence of a particle
of mass intermediate between the proton and the electron’, J. C. Street
and E. C. Stevenson, Phys. Rev.
**52**, 1003 (1937). *“How do we know that the tau (τ) lepton exists?”*- ‘Evidence for anomalous lepton production in
e
^{+}- e^{-}annihilation’, M. L. Perl*et al.*, Phys. Rev. Lett. 35m 1489 (1975). *"How do we know that the charm quark exists?"*- 'Experimental observation of a
heavy J' , J. J. Aubert
*et al*., Phys. Rev. Lett.**33**, 1404 (1974). - 'Discovery of a
narrow resonance in e
^{+}e^{-}annihilation', J. -E. Augustin*et al*. Phys. Rev. Lett.**33**, 1406 (1974). - B. Richter and S. Tang (the
leaders of the two experiments cited above) shared the Nobel Prize in Physics in
1976.
*"How do we know that the bottom quark exists?"*- 'Observation of a dimuon resonance
at 9.5 GeV in 400-GeV proton-nucleus collisions', S. W.
Herb
*et al*., Phys. Rev. Lett.**39**, 252 (1977). *"How do we know that the top quark exists?"*- 'Search for high mass top quark
production in p pbar collisions at Sqrt(s) = 1.8 TeV', S. Abachi
*et al*. (D0 Collaboration), Phys. Rev. Lett.**74**, 2422 (1995). - 'Observation of
top quark production in pbar p collisions with
the Collider Detector at Fermilab', F. Abe
*et al*. (CDF Collaboration), Phys Rev. Lett.**74**, 2626 (1995). *“How do we know that the gluon exists?”*Are there direct tests that produce gluons?- ‘Discovery of three-jet events and a test of
quantum chromodynamics at PETRA’, D. P. Barber
*et al*. (MARK-J Collaboration), Phys. Rev. Lett.**43**, 830 (1979). - ‘Evidence for planar events in e
^{+}e^{-}annihilation at high energies’, R. Brandelik*et al*. (TASSO Collaboration) Phys. Lett.**86B**, 243 (1979). - ‘Evidence for gluon bremsstrahlung in e
^{+}e^{-}annihilations at high energies’, Ch. Berger*et al*. (PLUTO Collaboration), Phys. Lett.**86B**, 418 (1979). - ‘Observation of planar three-jet events in e
^{+}e^{-}annihilation and evidence for gluon bremsstrahlung’, W. Bartel*et al*. (JADE Collaboration), Phys. Lett.**91B**, 142 (1980). *"How do we know that the Higgs boson exists?"*- 'Observation of a new boson at a
mass of 125 GeV with the CMS experiment at the LHC', CMS
Collaboration, Phys. Lett. B
**716**30-61 (2012). - 'Observation of
a new particle in the search for the standard model Higgs boson with the
ATLAS detector at the LHC', ATLAS Collaboration, Phys. Lett. B
**716**, 1-29 (2012). - The prediction of a Higgs
boson has been attributed to a number of people, but F. Englert and P. W. Higgs shared the Nobel Prize in Physics in
2013.
*"How did they confirm the prediction of a particle consisting of three strange (or s) quarks"?*('strangeness minus three' as it was called)- 'Observation of a hyperon with
strangeness minus three', W. E. Barnes
*et al*., Phys. Rev. Lett.**12**, 204 (1964). - There is a very
retro-looking 1964 BBC documentary about
this discovery.
*"How do we know that neutrinos exist"?*__Electron neutrino__: 'Detection of the free neutrino: A confirmation', C. L. Cowan, F. Reines, F. B. Harrison, H. W. Kruse, and A. D. McClure, Science**124**, 103 (1956).- F. Reines shared the Nobel
Prize in Physics in 1995 for this discovery.
__Muon neutrino__: 'Observation of high-energy neutrino reactions and the existence of two kinds of neutrinos', G. Danby*et al*., Phys. Rev. Lett.**9**, 36 (1962).- Three
of the co-authors of this paper shared the Nobel
Prize in Physics in 1988.
__Tau neutrino__: 'Observations of tau neutrino interactions' K. Kodama*et al*. (DONUT Collaboration), Phys. Lett. B**504**, 218 (2001).*"How do we know that there are only three (light) neutrinos?"*- 'Single- and multi-photon events
with missing energy in e
^{+}e^{-}collisions at LEP', P. Achard*et al*. (L3 Collaboration), Phys. Lett. B**587**, 16 (2004). *“How do we know that neutrinos oscillate (change their ‘flavor’)?”*- ‘Evidence for oscillation of atmospheric
neutrinos’,
Y. Fukuda
*et al.*, (Super-Kamiokande Collaboration) Phys. Rev. Lett.**81**, 1562 (1998). - ‘Direct evidence for neutrino flavor
transformations from neutral-current interactions in the Sudbury Neutrino
Observatory’,
Q. R. Ahmad
*et al*., (SNO Collaboration) Phys. Rev. Lett.**89**, 011301 (2002). - T. Kajita
(Super-Kamiokande Collaboration) and A.
McDonald (SNO Collaboration) shared the Nobel Prize in Physics in
2015
for
*‘…the discovery of neutrino oscillations which showed that neutrinos have mass*…’ *“How do we know that there are heavy bosons which mediate the weak interactions or at least how were they discovered?’*__Discovery of the W boson__:- ‘Experimental observation
of isolated large transverse electrons with associated missing energy at
√(s) = 540 GeV’, G. Arnison
*et al*. (UA1 Collaboration), Phys. Lett.**122B**, 103 (1983). - ‘Observation of single isolated electrons at
high transverse momentum in events with missing transverse energy at the
CERN pbar p collider’,
M. Banner
*et al*. (UA2 Collaboration), Phys. Lett.**122B**, 476 (1983). __Discovery of the Z boson__:- ‘Experimental observation
of lepton pairs of invariant mass around 95 Gev/c2
at the CERN SPS collider’, G. Arnison
*et al*. (UA1 Collaboration), Phys. Lett. 126B, 398 (1983). - ‘Evidence for Z
^{0}→ e^{+}e^{-}at the CERN pbar p collider’, P. Bagnaia*et al*. (UA2 Collaboration), Phys. Lett. B129, 130 (1983) - Amongst the many physicists
who contributed to the construction of the CERN accelerator complex and
the UA1/UA2 experiments which led to these discoveries, two were cited
for the Nobel Prize in Physics in
1984,
C. Rubbia and S. van der Meer.
*“How do we know what the charge of the electron is?”*- ‘On the elementary electrical charge and the
Avogadro constant’, R. A. Millikan, Phys. Rev.
**2**, 109 (1913) *"How do we know that the photon is massless? or what are the limits on its mass?"*__Laboratory limit__: 'New experimental test of Coulomb's law: A laboratory upper limit on the photon rest mass', E. R. Williams, J. E. Faller, and H. A. Hill, Phys. Rev. Lett.**26**, 721 (1971).__Using plasma physics/astrophysical observations__: 'Using plasma physics to weigh the photon'__,__D. D. Ryutov, Plasma Phys. Control. Fusion**49**, B429 (2007).__Review of many different types experimental bounds__: 'Terrestrial and extraterrestrial limits on the photon mass', A. S. Goldhaber and M. M. Nieto, Rev. Mod. Phys.**43**, 277 (1971).*"How do we know that the photon is electrically neutral? or what are the limits on its charge?*- 'Pulsar bound on the photon
electric charge reexamined', G. Raffelt,
Phys. Rev. D
**50**, 7729 (1994). *"How do we know that the charge of the electron and proton are equal and opposite? or to what extent do we know that matter is electrically neutral?"*- 'Neutrality of molecules by a new
method', H. F. Dylla and J. G. King, Phys. Rev. A
**7**, 1224 (1973). *“How do we know that there is a neutron?”*- ‘Possible evidence of a neutron’, J. Chadwick,
Nature
**129**, 312 (1932). - J. Chadwick was
awarded the Nobel Prize in Physics in
1935 for this discovery.
*"How do we know that the electron has an anti-particle?"*- 'The positive electron', C. D.
Anderson, Phys. Rev.
**43**, 491 (1933). - Anderson shared
the Nobel Prize in Physics in
1936 for this discovery.
*"How do we know that the proton has an anti-particle?"*- 'Observation of antiprotons', O.
Chamberlain, E. Segrè, C. Wiegand,
and T. Ypsilantis, Phys. Rev.
**100**, 947 (1955). - Segrè and Chamberlain shared the Nobel Prize in Physics in
1959 for this discovery.
*"How do we know that that anti-hydrogen exists?"*- 'Production of antihydrogen', G. Baur
*et al*. (PS210 Collaboration), Phys. Lett. B**368**, 251 (1996). - 'Observation of
atomic antihydrogen', G. Blandford
*et al*., Phys. Rev. Lett.**80**, 3037 (1998).

**Atomic
physics:**

*"How do we know what the momentum-space wavefunction, φ(p), of the hydrogen atom look like?"*- 'Direct
measurement of the electron momentum probability distribution in atomic
hydrogen', B. Lohmann and E.
Weigold, Phys. Lett. A
**86**, 139 (1981). *"How do we know that unstable particles can form atoms the same way electrons do?"*__Muons__: 'The energy levels of muonic atoms', E. Borie and G. A. Rinker, Rev. Mod. Phys.**64**, 67 (1982).__Pions__: 'Pionic atoms', G. Backenstoss, Ann. Rev. Nucl. Sci.**20**, 467 (1970)__Kaons__: 'Kaonic and other exotic atoms', R. Seki and C. E Wiegand, Ann. Rev. Nuc. Sci.**25**, 241 (1975).*"How do we know that electronic wavepackets in atoms can exhibit classical periodic motion?*- 'Classical periodic
motion of atomic-electron wave packets', J. A. Yeazell, M. Mallalieu, J. Parker, and C. R. Stroud, Jr., Phys.
Rev A
**40**, 5040 (1989). *"How do we know that electronic wavepackets in atoms also exhibit non-classical quantum mechanical revival behavior?*Spreading out but eventually reforming into something like their original state.- 'Observation of
the collapse and revival of a Rydberg electronic wave packet', J. A. Yeazell, M. Mallalieu, and C. R. Stroud, Jr., Phys. Rev. Lett.
**64**, 2007 (1990). *"How do we know that integral spin objects undergo Bose-Einstein condensation (so-called BEC) at low temperatures?"*- 'Observation of
a Bose-Einstein condensation in a diluate
atomic vapor', M. H. Anderson, J. R. Ensher,
M. R. Mathews, C. E. Wieman, and E. A. Cornell,
Science
**269**, 198 (1995). - E. Cornell, W. Ketterle, and C. E. Wieman
shared the Nobel Prize in Physics in 2001 for their work on BECs.
*"How do we know that Bose-Einstein condensates have a common quantum phase?" -*Hint: Do two condensates interfere with each other the way other coherent waves can?- 'Observation of
interference between two Bose condensates', M. R. Andrew
*et al*., Science**275**, 637 (1997). *"How do we know that fundamental constants of nature (for example the fine structure constant, α) don't vary with time?*- 'New limits on
the drift of fundamental constants from laboratory measurements', M. Fisher
*et al*., Phys. Rev. Lett.**92**, 230802 (2004). - They find that the ratio of
change of the fine structure constant, α, is (dα/dt)/α = (-0.9 +/- 2.9) x 10
^{-15}yr^{-1}.

**Condensed
matter physics**:

*“How do we know about the history of superconductivity?”*- I can’t find
the original paper by H. Kamerlingh Onnes in electronic form but his Nobel Prize talk
about how he first became interested in low-temperature physics, learned
how to cool gases down to very low temperatures, liquefy helium, and then
make measurements of materials properties at a few degrees K is nice
review: See ‘Investigations into the
properties of substances at low temperatures, whicih
have led, amongst other things, to the preparation of liquid helium’, H. Kameerlingh Onnes, Nobel
Lecture Dec. 11, 1913.
*“How do we know that high temperature superconductors exist?”*- ‘Possible high T
_{C}superconductivity in the Ba-La-Cu-O system’, J. G. Bednorz and K. A Müller, Z. Phys. B (Condensed Matter)**64**, 189 (1986). - Bednorz and Müller shared the Nobel Prize in Physics in
1987 for this discovery.
*"How do we know that resistance is quantized in certain materials, independent of sample size?"*- 'New method for
high-accuracy determination of the fine-structure constant based on
quantized Hall resistance', K. v. Klitzing, G. Dorda,
and M. Pepper, Phys. Rev. Lett.
**45**, 494 (1980). - Von Klitzing won the Nobel Prize in Physics in
1985
for this discovery.
*"How do we know that the circulation in superfluid helium is quantized?"*- 'Observation of
quantized circulation in superfluid helium', S. C. Whitmore and W.
Zimmerman, Jr., Phys. Rev.
**166**, 181 (1968). - 'The detection
of single quanta of circulation in liquid Helium II', W. F. Vinen,
Proc. of the Royal Society, Series A, Mathematical and Physical Sciences
**260**, 218 (1961). *"How do we know that the magnetic flux in a superconductor is quantized?"*- 'Experimental
proof for quantized flux in superconducting cylinders', B. S. Deaver,
Jr. and W. M. Fairbank, Phys. Rev. Lett.
**7**, 43 (1961). - 'Experimental
proof of magnetic flux quantization in a superconducting ring', R. Doll and M. Näbauer, Phys. Rev. Lett.
**7**, 51 (1961). *“How do we know how scanning tunneling microscopy works?”*- ‘Surface studies by
scanning tunneling microscopy’, G. Binning, H. Rohrer,
Ch. Gerber and E. Weibel, Phys. Rev. Lett. 49,
57 (1982).
- Binning and Rohrer shared
the Nobel Prize in Physics in
1986
for this discovery.
*"How do we know that some materials exhibit giant magnetoresistance?"*- also known as GMR- 'Giant
magnetoresistance of (001)Fe/(001)Cr magnetic superlattices', M. N. Baibich
*et al*., Phys. Rev. Lett.**61**, 2472 (1988) - 'Enhanced
magnetoresistance in layered magnetic structures with antiferromagnetic
interlayer exchange', G. Binasch, P. Grünberg, F. Saurenbach,
and W. Zinn, Phys. Rev. B
**39**, 4828 (1989). - Note that Albert Fert and Peter Grünberg shared the Nobel Prize Physics in 2007 for this discovery.
- Wikipedia describes GMR as
follows: "The main application of GMR is magnetic field
sensors, which are used to read data in hard disk drives, biosensors,
microelectromechanical systems (MEMS) and other devices. GMR multilayer
structures are also used in magnetoresistive
random-access memory (MRAM) as cells that store one bit of
information."
- “
*What were the first papers which described Density Functional Theory (DFT)?*” - “Electron Gas”, P. Hohenberg
and W Kohn, Phys. Rev.
**136**, B684 (1964). - “Self-consistent Equations
Including Exchange and Correlation Effects”, W. Kohn and L. J. Sham,
Phys. Rev.
**140,**A1133 (1965).

**Astronomy
and Astrophysics**:

*“How do we know that stars (including our sun) burn hydrogen into helium, generating neutrinos?”*– These papers describe the theoretical background and experimental realization of a 30 year long experiment (pioneered by Ray Davis) to detect neutrinos from the sun.- ‘Solar
neutrinos. I. Theoretical’, J. N. Bahcall, Phys. Rev.
Lett. 12, 300 (1964).
- ‘Solar
neutrinos. II. Experimental’,
R. Davis Jr., Phys. Rev. Lett.
**12**, 303 (1964). - ‘Measurement
of the solar electron neutrino flux with the Homestake
chlorine detector’, B.
Cleveland, T. Daily, R. Davis Jr., J. R. Distel,
K. Lande, C. K. Lee, and P. S Wildenhain, Ap. J.
**496**, 505 (1998). - R. Davis shared the Nobel Prize in Physics in 2002 for his long-term work on solar neutrino detection.
*“How do we know that the collapse of stars into supernovae generate neutrinos?”*- ‘Observation of a neutrino burst from the
supernova SN1987A’, K. Hirata
*et a*l. (Kamiokande II Collaboration), Phys. Rev. Lett. 58, 1490 (1987). - The observation
of these neutrinos almost immediately led to stringent bounds on the mass
of the electron neutrino. If neutrinos had too much mass, neutrinos of
different energy would have take different
lengths of time to arrive on earth, but a short (in time) pulse was
observed. Two papers which derived such bounds (including one by my Ph.D.
adviser!) are listed below.
- ‘Upper limit on the mass of the electron
neutrino’, J. N. Bahcall and S. I. Glashow,
Nature,
**326**, 476 (1987). - ‘Neutrino mass limits from SN1987A’, W. D. Arnett
and J. L. Rosner, Phys. Rev. Lett.
**58**, 1906 (1987). *"How do we know that there are extra-solar plants?"*- 'A planetary
system around the millisecond pulsar PSR1257+12', A. Wolszczan and D. A
Frail, Nature
**355**, 145-147 (1992).

**Cosmology**:

*"How do we know how the light elements were made during the evolution of the early universe?"*- 'The origin of the chemical
elements', R. A. Alpher, H. Bethe, and G. Gamow,
Phys. Rev.
**73**, 803 (1948). - Note the (very
intentional!) pun with the authors names --
first three letters of the Greek alphabet, α, β, and γ.
*"How do we know that there is a cosmic microwave background (CMB) in the universe, and what its temperature is?"*- Theory
(background): 'Cosmic
black-body radiation', R. H. Dicke,
P. J. E. Peebles, P. G. Roll, and D. T. Wilkinson, Ap. J.
**142**, 414 (1965). - Experiment 'A measurement
of excess antenna temperature at 4080 Mc/s', A. A. Penzias and R. W
Wilson, Ap. J.
**142**, 419 (1965). *"How do we know that the CMB is the best black-body spectrum ever discovered"? -*like ever!- 'A preliminary measurement of the
cosmic microwave background spectrum by the Cosmic Backgrond Explorer (COBE) satellite', J. C.
Mather
*et al*., Ap. J.**354**L37 (1990). - J. C. Mather
and G. F. Smooth shared the Nobel Prize in Physics in
2006 for this discovery.
*“Why do we think that there is a maximum energy to cosmic rays?”*– due to their interaction with the cosmic microwave background (CMB).- ‘End of the cosmic-ray spectrum’, K. Greisen,
Phys. Rev. Lett.
**16**, 748 (1966). - ‘Upper limit of the spectrum of cosmic rays’, G. T. Zatsepin and V. A. Kuz’min,
JETP Letters,
**4**, 78 (1966). - This limit has
been named the GZK cutoff (after the three authors) and the maximum
energy is of order 10
^{20 }eV.

**Classical
mechanics and electricity/magnetism**:

*“How do we know that there is deterministic chaos?”*- ‘Deterministic non-periodic flow’, E. Lorenz, J.
Atmos. Sci.
**20**, 160 (1963). - This was one of
the first papers to demonstrate that many physical and mathematical
dynamical systems can exhibit ‘
*sensitive dependence on initial conditions*’, one of the hallmarks of chaos. *"How do we now that terrestrial gravity works on things as small as neutrons?"*- 'Gravitational
acceleration of free neutrons', J. W. T. Dabbs, J. A.
Harvey, D. Paya, and H. Horstmann,
Phys. Rev.
**139B**, 756 (1965). *"How do we know that Coulomb's law behaves as 1/r*^{2}?"- 'A very accurate
test of Coulomb's law of force between charges', Phys. Rev.
**50**, 1066 (1936).

^{*} - "To understand the future, we have to go back in
time"

From *'Back in Time' **- written by Armandano
Christian Perez (a.k.a. **Pitbull**), Adrian Trejo, Urales Vargas, Sylvia
Robinson, Mickey Baker, Ellas Mcdaniel,
and March Kinchen. *

^{†}* - R. W. Robinett
rq9@psu.edu
Last updated 02/28/2018*