"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/r²? -- 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 = γmc² 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 “Uber Gravitatationalswellen” and you can find a translation here.
• "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 direct detection of gravity waves!
• “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 Na₂ molecules', M. S. Chapman et al., Phys. Rev. Lett. 74, 4783 (1995).
• Buckeyballs (C₆₀) 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 Electrodynamics (QED) works so well? - Allowing theory and experiment to agree to 12 decimal places, at least for a very few special physical quantities?
• '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. D85, 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⁺ π⁰ 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 Z⁰ → 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).
• Walter Kohn shared the Nobel prize (in Chemistry) for his work on Density Functional Theory in 1998

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 al. (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 10²⁰ 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/r²?"
• '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