{{short description|American astronomer and physicist (1916–1997)}} {{primary sources|date=June 2010}} {{Use mdy dates|date=December 2018}} {{Infobox scientist | image = | birth_name = Robert Henry Dicke | birth_date = {{birth date|1916|05|06}} | birth_place = [[St. Louis, Missouri]], U.S. | death_date = {{death date and age|1997|03|04|1916|05|06}} | death_place = [[Princeton, New Jersey]], U.S. | field = [[Physics]] | work_institutions = Princeton University | education = [[Princeton University]] (B.S.)<br/>[[University of Rochester]] (Ph.D) | known_for = Inventing the [[lock-in amplifier]]<br/>[[Dicke model]]<br/>[[Brans–Dicke theory]]<br/>[[Dicke effect]]<br/>[[Dicke radiometer]]<br />[[Lamb Dicke regime]]<br />Coining the term "[[black hole]]" | spouse = {{marriage|Annie Currie|1942}} | children = 3 | doctoral_advisor = [[Lee Alvin DuBridge]] | prizes = {{no wrap|[[National Medal of Science]] (1970)<br/>[[Comstock Prize in Physics]] (1973)<br/>[[Elliott Cresson Medal]] (1974)<br/>[[Beatrice M. Tinsley Prize]] (1992)}} | religion = | signature = Robert_Henry_Dicke_autograph.jpg }} {{Cosmology|scientists}}
'''Robert Henry Dicke''' ({{IPAc-en|ˈ|d|ɪ|k|i}}; May 6, 1916 – March 4, 1997) was an American astronomer and [[physicist]] who made important contributions to the fields of [[astrophysics]], [[atomic physics]], [[physical cosmology|cosmology]] and [[gravity]].<ref>{{cite journal|author=Happer, William|author-link=William Happer|author2=Peebles, James|author2-link=Jim Peebles|author3=Wilkinson, David|author3-link=David Todd Wilkinson|title=Obituary: Robert Henry Dicke|journal=Physics Today|date=September 1997|volume=50|issue=9|pages=92–94|doi=10.1063/1.881921|bibcode=1997PhT....50i..92H|df=dmy-all|doi-access=free}}</ref> He was the [[Albert Einstein Professor in Science]] at [[Princeton University]] (1975–1984).<ref>{{Cite web |title=A Cosmic Journey: A History of Scientific Cosmology |url=https://history.aip.org/exhibits/cosmology/index.htm |access-date=2022-12-24 |website=history.aip.org}}</ref><ref>{{cite book |chapter=Robert Dicke and atomic physics |date=2016-05-06 |url=https://www.worldscientific.com/doi/10.1142/9789813142527_0007 |title=Physics Matters |pages=73–84 |publisher=WORLD SCIENTIFIC |doi=10.1142/9789813142527_0007 |isbn=978-981-314-250-3 |access-date=2022-12-24|url-access=subscription }}</ref><ref>{{Cite web |last=Archives |first=L. A. Times |date=1997-03-06 |title=Robert Dicke; Theorized That Big Bang 'Echo' Still Resonates |url=https://www.latimes.com/archives/la-xpm-1997-03-06-mn-35420-story.html |access-date=2022-12-24 |website=Los Angeles Times |language=en-US}}</ref>
==Biography== Born in [[St. Louis, Missouri]], Dicke completed his [[bachelor's degree]] at [[Princeton University]] and his doctorate, in 1939, from the [[University of Rochester]] in [[nuclear physics]]. During the Second World War he worked in the [[RadLab|Radiation Laboratory]] at the [[Massachusetts Institute of Technology]] where he worked on the development of [[radar]] and designed the [[Dicke radiometer]], a microwave receiver. He used this to set a limit on the temperature of the [[microwave background radiation]], from the roof of the Radiation Laboratory, of less than 20 [[kelvin]]s.
In 1946, he returned to Princeton University, where he remained for the remainder of his career. He did some work in atomic physics, particularly on the [[laser]] and measuring the [[gyromagnetic ratio]] of the electron. An important contribution to the field of [[spectroscopy]] and radiative transfer was his prediction of the phenomenon called Dicke narrowing: When the mean free path of an atom is much smaller than the wavelength of one of its radiation transitions, the atom changes velocity and direction many times during the emission or absorption of a photon. This causes an averaging over different Doppler states and results in an atomic linewidth that is much narrower than the Doppler width.<ref>{{cite journal | author = R. H. Dicke | title = The Effect of Collisions upon the Doppler Width of Spectral Lines | journal = Physical Review | volume = 89 | issue = 2 | page = 472 | date = 1953 | doi = 10.1103/PhysRev.89.472|bibcode = 1953PhRv...89..472D }}</ref> Dicke narrowing occurs at relatively low pressures in the millimeter wave and microwave regions (where it is used in atomic clocks to improve precision). Dicke narrowing is analogous to the [[Mössbauer effect]] for gamma rays.
In 1956, approximately two years before [[Charles Hard Townes]] and [[Arthur Leonard Schawlow]] filed their patent application, Dicke filed a patent titled "Molecular Amplification Generation Systems and Methods" with claims of how to build an infrared [[laser]] and the use of an open [[resonator]] and the patent was awarded on September 9, 1958.
He spent the remainder of his career developing a program of precision tests of [[general relativity]] using the framework of the [[equivalence principle]]. In 1957, he first proposed an alternative theory of gravitation inspired by [[Mach's principle]] and [[Paul Dirac]]'s [[Dirac large numbers hypothesis|large numbers hypothesis]].<ref>{{cite journal | author = R. H. Dicke | title = Gravitation without a Principle of Equivalence | journal = Reviews of Modern Physics | volume = 29 | issue = 3 | pages = 363–376| date = 1957 | doi = 10.1103/RevModPhys.29.363|bibcode = 1957RvMP...29..363D }}</ref> In 1961, this led to the [[Brans–Dicke theory]] of gravitation,<ref>{{cite journal | author = C. Brans |author2=R. H. Dicke | title = Mach's Principle And A Relativistic Theory Of Gravitation | journal = Physical Review | volume = 124 | issue = 3 | page = 925 | date = 1961 | doi = 10.1103/PhysRev.124.925|bibcode = 1961PhRv..124..925B }}</ref> developed with [[Carl H. Brans]], an equivalence-principle violating modification of general relativity. A highlight experiment was the test of the equivalence principle by Roll, Krotkov and Dicke, which was a factor of 100 more accurate than previous work.<ref>{{cite journal | title = The equivalence of inertial and passive gravitational mass | author = Roll, P. G. | author2 = Krotkov, R. | author3 = Dicke, R. H. | date = 1964 | journal = Annals of Physics | volume = 26| issue =3|pages=442–517 | doi = 10.1016/0003-4916(64)90259-3|bibcode = 1964AnPhy..26..442R }}</ref> He also made measurements of [[sun|solar]] oblateness which were useful in understanding the [[apsis|perihelion]] [[Precession of perihelion|precession]] of [[Mercury (planet)|Mercury's]] [[orbit]], one of the classical tests of general relativity.<ref>{{cite journal | author = R. H. Dicke | author2 = H. M. Goldenberg | name-list-style = amp | title = Solar Oblateness and General Relativity | journal = Physical Review Letters | volume = 18 | issue = 9 | page = 313 | date= 1967 | doi = 10.1103/PhysRevLett.18.313 | bibcode=1967PhRvL..18..313D}}</ref>
[[Dirac large numbers hypothesis|Dirac had hypothesized]] that because the [[gravitational constant]] ''G'' is very roughly equal to the inverse [[age of the universe]] in certain units, then ''G'' must vary to maintain this equality. Dicke realized that Dirac's relation could be a [[selection effect]]: fundamental physical laws connect ''G'' to the lifetime of what are called [[main sequence]] stars, such as the Sun, and these stars, according to Dicke, are necessary for the existence of life.<ref>{{cite journal | author = Dicke, R. H. | journal = Nature | title = Dirac's Cosmology and Mach's Principle | volume = 192 | issue = 4801 | pages = 440–441| date = 1961 | doi = 10.1038/192440a0|bibcode = 1961Natur.192..440D | s2cid = 4196678 }}</ref> At any other epoch, when the equality did not hold, there would be no intelligent life around to notice the discrepancy. This was the first modern application of what is now called the [[weak anthropic principle]].
In the early 1960s, work on Brans–Dicke theory led Dicke to think about the early Universe, and with [[Jim Peebles]] he re-derived the prediction of a [[cosmic microwave background]] (having allegedly forgotten the earlier prediction of [[George Gamow]] and co-workers). Dicke, with [[David Todd Wilkinson]] and Peter G. Roll, immediately began building a Dicke radiometer to search for the radiation. They were preceded by the [[Discovery of cosmic microwave background radiation|accidental detection]] made by [[Arno Penzias]] and [[Robert Woodrow Wilson]] (also using a Dicke radiometer), who were working at [[Bell Labs]] near Princeton.<ref>{{cite book | author = R. B. Partridge | title = 3 K: The Cosmic Microwave Background Radiation | date = 1995 |publisher = Cambridge University Press | isbn = 0-521-35808-6}}</ref><ref>{{cite journal|last1=Penzias|first1 = A.A.|last2 = Wilson|first2=R.W.|title=A Measurement of Excess Antenna Temperature at 4080 Mc/s|journal=[[Astrophysical Journal]]|volume=142|pages=419–421|date=1965|doi=10.1086/148307|bibcode=1965ApJ...142..419P|doi-access=free}}</ref> Nevertheless, Dicke's group made the second clean detection, and their theoretical interpretation of Penzias and Wilson's results showed that theories of the early universe had moved from pure speculation into well-tested physics.<ref>{{cite journal | author = Dicke, R. H. | author2 = Peebles, P. J. E. | author3 = Roll, P. G. | author4 = Wilkinson, D. T. | date = 1965 | title = Cosmic Black-Body Radiation | journal = Astrophysical Journal | volume = 142 | pages = 414–419 | doi = 10.1086/148306 | bibcode=1965ApJ...142..414D}}</ref><ref>{{Cite web |last=Levesque |first=Emily |date=2022-05-08 |title=The Race to Prove the Existence of Cosmic Microwave Background |url=https://www.wondriumdaily.com/the-race-to-prove-the-existence-of-cosmic-microwave-background/ |access-date=2022-12-24 |website=Wondrium Daily |language=en-US |archive-date=December 8, 2022 |archive-url=https://web.archive.org/web/20221208062553/https://www.wondriumdaily.com/the-race-to-prove-the-existence-of-cosmic-microwave-background/ |url-status=dead }}</ref>
In 1970, Dicke argued that the universe must have very nearly the [[Critical density (cosmology)|critical density]] of matter needed to stop it expanding forever.<ref>{{cite book | author = Dicke, R. H. | title = Gravitation and the Universe| url = https://archive.org/details/gravitationunive0000dick | url-access = registration | date = 1970 | publisher =American Philosophical Society| bibcode = 1970grun.conf.....D}}</ref> [[Friedmann equations|Standard models]] of the universe pass through stages dominated by radiation, matter, curvature etc. Transitions between stages are very special cosmic times which ''a priori'' could differ by many orders of magnitude. Since there is a non-negligible amount of matter, either we are coincidentally living close to the transition to or from the matter-dominated stage, or we are in the middle of it; the latter is preferred since the coincidences are highly unlikely (an application of the [[Copernican principle]]). This implies a negligible curvature, so the universe must have almost critical density. This has been called the "Dicke coincidence" argument.<ref>{{cite book | author = Peebles, P. J. E. | title = Principles of Physical Cosmology | url = https://archive.org/details/principlesofphys00pjep | url-access = registration | publisher = Princeton University Press | date = 1993 | isbn = 0-691-07428-3}}</ref> In fact it gives the wrong answer, since we seem to be living at the time of transition between the matter and [[dark energy]] stages. An anthropic explanation of the failure of Dicke's argument was given by [[Steven Weinberg|Weinberg]].<ref>{{cite journal | author = Weinberg, S. | title = Anthropic bound on the cosmological constant | journal = Physical Review Letters| volume = 59| pages = 2607–2610| date = 1987 | doi = 10.1103/PhysRevLett.59.2607 | pmid = 10035596 | issue = 22 | bibcode=1987PhRvL..59.2607W}}</ref>
Dicke was also responsible for developing the [[lock-in amplifier]], which is an indispensable tool in the area of applied science and engineering.<ref>{{Cite web|last=Hageman|first=Steve|date=2017-12-27|title=Design a DSP lock-in amplifier, Part 1: Background|url=https://www.edn.com/design-a-dsp-lock-in-amplifier-part-1-background/|url-status=live|archive-url=https://web.archive.org/web/20210603101122/https://www.eetimes.com/digital-lock-in-amplifiers-theory-and-design/|archive-date=2021-06-03|access-date=2021-06-03|website=EDN|language=en-US}}</ref> Many of Dicke's experiments capitalize on lock-in in some way or another.{{Citation needed|date=September 2008}} However, in an interview with [[Martin Harwit]] he claims that even though he is often credited with the invention of the device; he believes he read about it in a review of scientific equipment written by Walter C. Michels, a professor at Bryn Mawr.<ref>{{cite web|url=http://www.aip.org/history/ohilist/4572.html |title=Oral History Transcript — Dr. Robert Dicke |publisher=Aip.org |date=June 18, 1985 |access-date=January 2, 2014}}</ref><ref name=Michels1941>{{Cite journal | last1 = Michels | first1 = W. C. | last2 = Curtis | first2 = N. L. | doi = 10.1063/1.1769919 | title = A Pentode Lock-In Amplifier of High Frequency Selectivity | journal = Review of Scientific Instruments | volume = 12 | issue = 9 | page = 444 | year = 1941 |bibcode = 1941RScI...12..444M | doi-access = free }}</ref>
Dicke is also credited with the invention of a kind of radio receiver, called a "Dicke Radiometric Receiver" or simply "Dicke Radiometer", developed by Dicke during WWII.<ref>{{Cite web | url=https://www.microwaves101.com/microwave-encyclopedia/radiometric-receivers |title = Radiometric Receivers}}</ref> His radiometer was characterized by a noise temperature calibration technique using a switchable resistor, known as "Dicke Resistor".
Dicke was awarded the 1970 [[National Medal of Science]].<ref>{{cite web|url=https://new.nsf.gov/honorary-awards/national-medal-science/recipients?query=Dicke |title=National Science Foundation - The President's National Medal of Science |publisher=Nsf.gov |access-date=January 8, 2024}}</ref> In 1973, he was awarded the [[Comstock Prize in Physics]] from the [[United States National Academy of Sciences|National Academy of Sciences]], of which he was a member.<ref name="Comstock">{{cite web|title=Comstock Prize in Physics|url=http://www.nasonline.org/site/PageServer?pagename=AWARDS_comstock|publisher=National Academy of Sciences|access-date=February 13, 2011|archive-url=https://web.archive.org/web/20101229195326/http://www.nasonline.org/site/PageServer?pagename=AWARDS_comstock|archive-date=December 29, 2010|df=dmy-all}}</ref><ref>{{Cite web |title=Robert H. Dicke |url=http://www.nasonline.org/member-directory/deceased-members/56318.html |access-date=2022-07-13 |website=www.nasonline.org}}</ref> He was also a member of the [[American Academy of Arts and Sciences]] and the [[American Philosophical Society]].<ref>{{Cite web |title=Robert Henry Dicke |url=https://www.amacad.org/person/robert-henry-dicke |access-date=2022-07-13 |website=American Academy of Arts & Sciences |language=en}}</ref><ref>{{Cite web |title=APS Member History |url=https://search.amphilsoc.org/memhist/search?creator=Robert+H.+Dicke&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced |access-date=2022-07-13 |website=search.amphilsoc.org}}</ref> Dicke was nominated for the [[Nobel Prize in Physics]] multiple times.<ref>{{Cite web |date=2020-04-01 |title=Robert Henry Dicke |url=https://www.nobelprize.org/nomination/archive/show_people.php?id=10761 |access-date=2022-04-05 |website=NobelPrize.org |language=en-US}}</ref> Peebles ended his own 2019 Nobel Lecture with a statement of disappointment that Dicke had never been awarded the prize, then said, "But I am satisfied now because my Nobel Prize is closure of what Bob set in motion, his great goal of establishing an empirically based gravity physics, by the establishment of the empirically-based relativistic cosmology."<ref>{{cite journal | last1 = Peebles | first1 = P. J. E. | title = Nobel Lecture: How Physical Cosmology Grew |url=https://www.nobelprize.org/uploads/2019/10/peebles-lecture.pdf | journal = Reviews of Modern Physics | date = 2020 | volume = 92 | issue = 3 | article-number = 030501 | doi = 10.1103/RevModPhys.92.030501| bibcode = 2020RvMP...92c0501P | s2cid = 224985139 }}</ref>
== Marriage and family life == Dicke married Annie Currie in 1942. Currie, of [[Scottish people|Scottish]] descent, was born in [[Barrow-in-Furness]] in England in 1920 and as a young girl immigrated to Rochester, New York, via Australia and New Zealand, of which Annie had very fond memories.
At the beginning of World War II, Dicke was asked to assist the war effort by applying his skills to the development of radar with the Massachusetts Institute of Technology.
At the end of the war, Dicke and Currie moved to Princeton, New Jersey, where Robert was on the faculty at Princeton University. Dicke died there March 4, 1997. Currie continued to live in Princeton until 2002. For the last years of her life she lived in Hightstown, New Jersey at Meadow Lakes Retirement Community until her death in 2005.
They had one daughter, Nancy born in 1945, and two sons, John born in 1946 and James born in 1953. At the time of Dicke's death they had six grandchildren and a great grandchild.<ref>{{cite web|last1=Savani|first1=Jacquelyn|title=Princeton Physicist Robert Dicke Dies|url=https://www.princeton.edu/pr/news/97/q1/0304dick.html|website=Princeton University}}</ref>
==Bibliography== *{{Cite journal |pmid = 16592998 |last1=Dicke |date=April 1981 |title=Seismology and geodesy of the sun: Low-frequency oscillations |volume=78 |issue=4 |journal=[[PNAS|Proc. Natl. Acad. Sci. U.S.A.]] |pages=1989–1993 |doi = 10.1073/pnas.78.4.1989 |first1 = RH |pmc = 319267 |bibcode = 1981PNAS...78.1989D |doi-access=free }} *{{Cite journal |pmid= 16592985 |last1=Dicke |date=March 1981 |title=Seismology and geodesy of the sun: Solar geodesy |volume=78 |issue=3 |journal=[[PNAS|Proc. Natl. Acad. Sci. U.S.A.]] |pages=1309–1312 |doi = 10.1073/pnas.78.3.1309 |first1 = RH |pmc = 319117 |bibcode = 1981PNAS...78.1309D |doi-access=free }} *{{Cite journal |pmid = 17736508 |last1=Dicke |date=April 26, 1974 |title=The Oblateness of the Sun and Relativity |volume=184 |issue=4135 |journal=Science |pages=419–429 |doi = 10.1126/science.184.4135.419 |first1 = RH |bibcode = 1974Sci...184..419D }} *{{Cite journal |pmid = 17792834 |last1=Dicke |date=August 25, 1967 |title=Solar Models |volume=157 |issue=3791 |page=960 |doi = 10.1126/science.157.3791.960 |journal=Science |first1 = RH |bibcode = 1967Sci...157..960D |doi-access=free }} *{{Cite journal |pmid = 17829699 |last1=Dicke |date=November 9, 1962 |title=The Earth and Cosmology: The earth may be affected by the distant matter of the universe through a long-range interaction |volume=138 |issue=3541 |pages=653–664 |doi = 10.1126/science.138.3541.653 |journal=Science |first1 = RH |bibcode = 1962Sci...138..653D }} *{{Cite journal |pmid = 17735811 |last1=Dicke |date=March 6, 1959 |title=New Research on Old Gravitation: Are the observed physical constants independent of the position, epoch, and velocity of the laboratory? |volume=129 |issue=3349 |periodical=[[Science (journal)|Science]] |pages=621–624 |doi = 10.1126/science.129.3349.621 |first1 = RH |bibcode = 1959Sci...129..621D }} *{{Cite journal |last = Dicke |first = RH |date = 1946 |title = The measurement of thermal radiation at microwave frequencies |volume = 17 |issue = 7 |periodical = [[Review of Scientific Instruments]] |pages = 268–275 |doi = 10.1063/1.1770483 |bibcode = 1946RScI...17..268D |pmid=20991753|s2cid = 26658623 |doi-access = free }}
==References== {{Reflist|30em}}
==Sources== *{{cite journal | author = Kuhn J. R. | author2 = Libbrecht K. G. | author3 = Dicke R. H. | date = 1988 | title = The surface temperature of the sun and changes in the solar constant | journal = Science | volume = 242 | issue = 4880| page = 908 |bibcode=1988Sci...242..908K|doi = 10.1126/science.242.4880.908 | s2cid = 128820028 }} *{{cite journal | author = Williams J. G. | author2 = Dicke R. H. | author3 = Bender P. L.| author4 = Alley C. O. | author5 = Currie D. G.| author6 = Carter W. E. | author7 = Eckhardt D. H.| author8 = Faller J. E. | author9 = Kaula W. M. | display-authors = etal | date = 1976 | title = New test of the equivalence principle from lunar laser ranging | journal = Phys. Rev. Lett. | volume = 36 | issue = 11| page = 551 |bibcode=1976PhRvL..36..551W|doi = 10.1103/PhysRevLett.36.551 }} *{{cite journal | author = Peebles P. J. E. | author2 = Dicke R. H. | date = 1968 | title = Origin of the Globular Star Clusters | journal = Astrophys. J. | volume = 154 | page = 891 | bibcode=1968ApJ...154..891P|doi = 10.1086/149811 }} *{{cite journal | author = Dicke R. H. | date = 1962 | title = Mach's Principle And Invariance Under Transformation Of Units | journal = Phys. Rev. | volume = 125 | issue = 6| page = 2163 |bibcode=1962PhRv..125.2163D|doi = 10.1103/PhysRev.125.2163 }}
==External links== {{Wikiquote}} *[http://www.nasonline.org/member-directory/deceased-members/56318.html National Academy of Sciences biography] *{{cite journal |last1=Partridge |first1=Bruce |title=Obituary: Robert Henry Dicke, 1916-1997 |journal=Bulletin of the American Astronomical Society |date=1997 |volume=29 |issue=4 |page=1469 |bibcode=1997BAAS...29.1469P}} *{{cite journal |last1=Unzicker |first1=A. |title=Information in asset pricing: A wave function approach |journal=Annalen der Physik |date=2009 |volume=18 |pages=57–70 |doi=10.1002/andp.200810335 |arxiv=0708.3518}} *[https://www.aip.org/history-programs/niels-bohr-library/oral-histories/31508 Oral history interview transcript with Robert Dicke on 18 November 1975, American Institute of Physics, Niels Bohr Library & Archives] * [https://www.aip.org/history-programs/niels-bohr-library/oral-histories/4571 Oral history interview transcript with Robert Dicke on 2 May 1983, American Institute of Physics, Niels Bohr Library & Archives] * [https://www.aip.org/history-programs/niels-bohr-library/oral-histories/4572 Oral history interview transcript with Robert Dicke on 18 June 1985, American Institute of Physics, Niels Bohr Library & Archives] * [https://www.aip.org/history-programs/niels-bohr-library/oral-histories/33931 Oral history interview transcript with Robert Dicke on 19 January 1988, American Institute of Physics, Niels Bohr Library & Archives] * {{INSPIRE-HEP author}}
{{Authority control}}
{{DEFAULTSORT:Dicke, Robert H.}} [[Category:1916 births]] [[Category:1997 deaths]] [[Category:20th-century American physicists]] [[Category:20th-century American astronomers]] [[Category:American cosmologists]] [[Category:Members of the United States National Academy of Sciences]] [[Category:National Medal of Science laureates]] [[Category:People from Hightstown, New Jersey]] [[Category:Princeton University alumni]] [[Category:Scientists from Mercer County, New Jersey]] [[Category:Scientists from St. Louis]] [[Category:Physicists from Missouri]] [[Category:University of Rochester alumni]] [[Category:Winners of the Beatrice M. Tinsley Prize]] [[Category:Fellows of the American Physical Society]] [[Category:Members of the American Philosophical Society]] [[Category:MIT Radiation Laboratory people]]