TheTexas Symposium on Relativistic Astrophysics is an international scientific conference currently held once every two years, intended for astronomers, astrophysicists, and other researchers interested ingeneral relativity and its implications.[1] These gatherings helped end the insularity of the specialists of these diverse subjects[2][3]: 341 and marked the rise of modernastrophysics as a multidisciplinary area of research.[4][5] Today, these Symposia are among the most well-known in the domain ofgravitational physics.[6] They originally met inTexas, United States. But they proved highly successful that they were later held in many other places internationally, retaining the name.[7] A typical Texas Symposium has hundreds of attendees from around the world.[8]Ivor Robinson, one of the organizers of the first few Symposia, likely coined the term "relativistic astrophysics" in 1963.[8] Historians of science commonly mark the First Texas Symposium as the birth of the field.[4]
Judging from the quantities of scholarly activities, general relativity only entered the mainstream of research after the Second World War.[6] During the postwar decades, the growth of publications in general relativity wasenormous, faster than the overall (exponential) increase in physics as a whole.[9] The advent ofSpace Age, marked by the launch ofSputnik, the world's first artificial satellite, in 1957; the rise of radio, X-ray, andgamma-ray astronomy; and the parallels between the physics of (nuclear) explosives and supernovae—shock waves, massive energy outputs, and thesynthesis of heavy elements—fueled the growth of astronomy and astrophysics.[4] An increase in the number of researchers and funding in the postwar years also played a role.[6] Many physicists of the era recognized the need for collaboration across the domains of physics, both observational and theoretical, and for synthesizing different bodies of knowledge. This represented a pragmatic alternative to the more speculative approach towards aunified field theory on the basis offirst principles.[4] The U.S. Air Force and Navy provided funding for some the early conferences, but stopped doing so after Congress passed theMansfield Amendments, forbidding the use of the defense budget on basic research. The Texas Symposia were put in this category, despite the relevance of relativistic physics formissile guidance and the functioning of theGlobal Positioning System (GPS).[8] Up until the late 1960s the American military provided almost a fifth of the a funding for basic research, including 40 for physics.[10]: 140 Over the years, some of the recurring topics of interest at the Texas Symposia have beenastroparticle physics; thecosmic microwave background; extra-galacticgamma-ray bursts; gravitational waves;black holes, theirthermodynamics, andHawking radiation; pulsars; andX-ray astronomy.[8]
The First Symposium, chiefly organized by Robinson,Alfred Schild,Engelbert Schücking, andPeter Bergmann, convened inDallas, Texas, in December 16–18, 1963, shortly after theassassination of John F. Kennedy.[8] Some of the scientists invited thought that it would be disrespectful to hold a meeting so soon after the tragedy while others feared for their safety. But the mayor of Dallas sent themtelegrams asking them to come regardless.[11]
One of the major topic of discussion of the time was the optical andradio observations of quasi-stellar objects.[1]J. Robert Oppenheimer opened the first session on what would later be named "black holes" byJohn Archibald Wheeler.[1] Wheeler gave an extensive lecture on thegravitational collapse of stars, and expressed his enthusiasm for theOppenheimer–Snyder model.[3]: 240 Another notable speaker wasRoy Kerr, who gave a brief talk on his newfound exact solution to theEinstein field equations. With the notable exception ofAchilles Papapetrou, most physicists did not grasp its significance. But they later realized that theKerr metric described rotating black holes.[3]: 341–2 It was in fact the key to understanding quasars.[12]Hong-Yee Chiu used the wordquasar for quasi-stellar radio sources (QSRS) in the proceedings of this conference, published in 1965, though it took some time to become standard.[8] The First Symposium attracted approximately 300 people from many different countries worldwide. However, against the backdrop of theCold War, a number of physicists from the Soviet Union, such asVitaly Ginzburg andYakov Zeldovich, were not able to attend due to a ban from their own government or their inability to obtain a visa to visit the United States.[1][8] The gathering was sponsored byTexas Instruments, theRAND Corporation,Lockheed,Boeing, among others.[8] In his after-dinner speech,Thomas Gold commented on the significance of this conference: "...the relativists with their sophisticated works are not onlymagnificent cultural ornaments but might actually be useful to science! Everyone is pleased: the relativists who feel they are being appreciated and are experts in a field they hardly knew existed, the astrophysicists for having enlarged their domain, their empire, by the annexation of another subject—general relativity."[3]: 341
The Second Symposium convened at theUniversity of Texas at Austin in December 15–19, 1964. Discussions of quasars continued, now with astronomical observations at various portions of the electromagnetic spectrum, includingX-rays andgamma-rays. Astronomers exhibited their discoveries on highly energeticcosmic rays, such asneutrinos.Robert Dicke presented his improvedEötvös experiment, verifying theprinciple of equivalence to one part in 1011. The Symposium concluded with a seminar on gravitational collapse, the energy released from such an event, and the relevance of relativistic hydrodynamics in the strong-field regime.[2]
At the Fifth Symposium inAustin, Texas, in 1970, the biggest topics were black holes,theorems concerninggravitational singularities, specific results byStephen Hawking,Werner Israel, andBrandon Carter that could begeneralized for a rotating electrically charged black hole, andenergy extraction from rotating black holes. Participants also discussed active galactic nuclei; pulsars; alternatives to general relativity (especially theBrans–Dicke and otherscalar–tensor theories) andnull results in their experimental tests; thepost-Newtonian expansion; and white holes.[13] Hawking attended in hiswheelchair.[8]
By the time of the Sixth Symposium inNew York City, 1972, black holes had become a major topic of study.[14] Researchers presented their work onX-ray binaries,accretion disks, andCygnus X-1, the first black-hole candidate.[8] As of 2011, this Symposium was one of the most popular of all time, attended by around 1,000 people.[8]
The Seventh Symposium, organized in Dallas, 1974, saw the first scheduled parallel sessions.[8] Some major topics of interest were theabundance of the chemical elements, gamma-ray bursts,supernovae, galaxies,compact objects, and gravitational waves.[15]
Jocelyn Bell Burnell, co-discoverer ofpulsars, gave an after-dinner speech on her work at the Eighth Symposium inBoston, Massachusetts, in 1976,[16][8] at the invitation of Thomas Gold.[17] Other highlights of this conference were discussions of supernovae and stellar collapse; thermodynamics andquantum field theory in curved spacetime; X-ray astronomy; theHubble expansion; neutron stars;supergravity; and the use of computers innumerical relativity.[17]
At the Ninth Symposium inMunich, Germany, in 1978, the newly discoveredHulse–Taylor pulsar, named afterRussell Alan Hulse andJoseph Hooton Taylor Jr., attracted considerable attention as atest of general relativity outside of the solar system in the post-Newtonian limit. The observed orbital decay due to gravitational radiation andprecession of theperiastron were accurately predicted by general relativity.[18] This was the first Texas Symposium held in Europe.[8] More than 800 people were in attendance.[19]
Gravitational waves were a major topic at the Fourteen Symposium inChicago, Illinois, in 1986.[20]Kip Thorne shared his plans for what later became the Laser Interferometer Gravitational-Wave Observatory (LIGO).[3]: 498 Bernard Schultz examined how gravitational collapses, such as supernovae, as potential sources of gravitational waves and the prospects of detecting them byWeber bars (invented byJoseph Weber).[20] Other notable topics wereactive galactic nuclei;gravitational lenses and how they could be used to map the distribution ofdark matter and to determine theHubble constant;anisotropy in the cosmic microwave background and the upcomingCosmic Background Explorer (COBE) satellite; and NASA'sGreat Observatories program.[20]
By the 1990s, a largepublic lecture in the evening has become a standard feature. Stephen Hawking gave this talk at the Fifteenth Symposium inBrighton, United Kingdom, 1990.[8]
The Twenty-Sixth Symposium took place inSão Paulo, Brazil, in 2012. It was the first to be held in Latin America.[21]
The Twenty-Seventh Symposium returned to Dallas for the 50th anniversary of the First.[11] This event featured around table of the "veterans" of the original conference, co-chaired byWolfgang Rindler. Other sessions discussed theevolution of galaxies,neutron stars,supermassive black holes, the implications of theHiggs boson for cosmology, plus updates from thePlanck satellite and the Nuclear Spectroscopic Telescope Array (NuSTAR).[22]
The Twenty-Eighth Symposium met inGeneva, Switzerland, in 2015, commemorating the 100th anniversary of the completion of general relativity byAlbert Einstein. Among theplenary speakers,Thanu Padmanabhan spoke of thefirst century of general relativity,Mustapha Ishak of theexact solutions to the Einstein field equations having applications in astrophysics,Alessandra Buonanno of gravitational waves emitted bybinary systems, andAnna Watts of theequation of state for neutron stars.[23]
The Thirty-Second Symposium was held inShanghai, China, at theTsung-Dao Lee Institute ofShanghai Jiao Tong University in 2023. Shanghai is the first East Asian city to host the conference. It took place on the 60th anniversary of the First Symposium. Kip Thorne gave the opening speech online.[24] (See linkbelow.)
At the Thirty-Third Symposium, organized byArizona State University inTempe, Arizona, in 2025, plenary talks focused on the imaging of black holes using theEvent Horizon Telescope,gravitational-wave astronomy, observations by theJames Webb Space Telescope,little red dots, and theHubble tension.[25]
