Debate Over Optics in Early Art Is Focus at OSA Gathering pletely undercuts their evidence.” The controversy over the use of optical aids by early Renaissance Walter Liedtke, a curator at the Met- painters is cross-disciplinary and emotionally charged. ropolitan Museum of Art in New York City, says the distortions in the carpet id Martha Stewart need to engage justed the lens to bring different parts could come from the painting’s canvas Din insider trading? Did she engage of the design into focus, he says. “My having been stretched. And, he in insider trading? University of Ari- calculations agree with the measured stresses, there’s no reason to assume zona physicist Charles Falco asks changes in magnification to within the artist was painting everything these questions as a way of empha- 0.2%.” Where the carpet looks fuzzy, from life. “Many of the rooms are ob- sizing that whether early Renais- he adds, it’s outside the lens’s depth viously made up, artistic conventions. sance artists needed to use optical of field. It’s such calculations on geo- The idea that a painting represented aids in their paintings is a separate metrical distortions that convince an existing room wouldn’t have oc- question from whether they actually him: “We’re not saying that lenses are curred to [art historians].” Stork notes did use them. the only way to get the perspective that pinpricks show that Jan van The hypothesis that painters used right,” Falco said in his talk in Eyck’s 1432 portrait of Cardinal Al- optical aids as early as the 1420s was Rochester. “We’re saying that lenses bergati was magnified mechanically, put forward a few years ago by artist are the only way to get the perspective with a proportional compass. “All the David Hockney in his book Secret wrong in precisely the way I am show- evidence is against [optical aids],” he Knowledge: Rediscovering the Lost ing you they got it wrong.” Most of any says. Artists in the early Renaissance Techniques of the Old Masters (Studio given painting would have been done “didn’t have the knowledge, and they Books, 2001). Hockney said the use of by eyeball, he says. “But certain fea- didn’t have the materials.” optical aids would explain a sudden tures, perhaps 5% of a painting’s sur- The dispute turns on the state of increase in realism in art; if he’s right, face, was done with the aid of optics; the art of glass and mirrors. Were the the date artists are recognized as hav- 95% was not.” necessary optics knowledge and ma- ing used optical aids will be pushed Stork counters that other explana- terials available in the early Renais- back some 200 years. tions for the same distortions are sance? No, says Harvard University’s This fall, an Optical Society of more plausible. For example, studies Sara Schechner, a science historian America meeting in Rochester, New show all surviving Lotto-like carpets and curator specializing in early sci- York, brought together Falco, the are asymmetric, he says. “Hockney entific instruments. “I don’t think leading scientific voice supporting and Falco are fitting noise. It com- they had any knowledge of image Hockney; David Stork, the chief sci- entist at Ricoh Innovations in Palo Do deviations from symmetry in the geometrical carpet Alto, California, and the most vocal design in Lorenzo Lotto’s Husband and Wife indicate scientific opponent; and historians of that the artist used optical aids? The scientists most both art and science. “The last time I closely associated with the debate are proponent Charles saw something as animated as this Falco (standing) and opponent David Stork (inset). was [at the American Physical Society meeting in 1987] after the discovery of high-temperature superconductors,” says OSA president Peter Knight. “One side wants to believe that artists worked by trickery. The other side thinks it’s blasphemy. We spent the rest of the week arguing about it.” Knowledge and materials “I find the optical evidence over- whelming,” says Falco. He points to his calculations using Lorenzo Lotto’s 1523–24 painting Husband and Wife. From the painting’s 56% magnifica- tion—deduced by assuming that the woman’s shoulders are of average width—Falco calculates that the artist used a lens or concave mirror GROVER A. SWARTZLANDER JR/UNIVERSITY OF ARIZONA with a focal length of 54 cm. Given that, distortions in the perspective of the carpet design can be explained only by the artist’s having twice ad-

© 2004 American Institute of Physics, S-0031-9228-0412-340-5 December 2004 Physics Today 31 PT_issues1204.qxd 11/8/2004 2:17 PM Page 32

projection from mirrors onto a screen Art appreciation vast majority of art history, it’s a foot- in the 15th century.” Even if evidence Among physicists, the jury is still out. note. These questions are irrelevant, is found that they did have the knowl- “There was no smoking gun for Falco,” trivial, for art historians.” Moreover, edge, she adds, “it’s not going to says Knight, who left the meeting he adds, the optics claims “depend on change my argument that they didn’t leaning toward the con arguments. very narrow measurements. It all have the materials.” But others, such as John Wood, chief seems so unnecessary. By the time an But for many meeting attendees, artist had it all set up, he could have the door was left open by the thriving optical engineer for the Hubble Space Telescope, are swayed by the evidence knocked it off freehand. [The optics spectacles-manufacturing business in claims] underestimate the skill of the 15th-century Florence described by suggesting that early Renaissance artists.” Referring to a 1420s painting University of Massachusetts historian painters could have used optical aids. Vincent Ilardi. “The optical knowledge “Falco used basic optics calculations by Robert Campin, for which Hockney was certainly available. If the manu- to show focal lengths. It’s proceeded and Falco claim optical aids were used facturing capability was available, I like a scientific inquiry,” he says. “I in painting latticework on the back of see no reason why artists would not think appreciation of art is being ad- a bench, he adds, “Why don’t they step have been able to project images,” says vanced with everyone being inter- back and think, Why is the bench David Lindberg, a University of Wis- ested in this.” there anyway? An artist would say it consin historian of early optics. At the Liedtke, for his part, allows that makes a framing device for an impor- meeting, he adds, “the acrimony was Renaissance artists may have used tant head. Can’t people just appreciate electric. It was in the air.” some optical aids, but he says, “for the the painting?” Toni Feder Van Allen, at 90, Sifting Data, Writing Papers, and Enjoying Icon Status of us all of these years. Growing up on a small Iowa farm, James Van Allen enjoyed a “closely knit PT: That must have significantly family which had a strong resemblance to that of earlier pioneer families.” changed your thinking about the It was that solid beginning that spurred him on to a life of scholarship. Sun’s influence in the solar system. VAN ALLEN: It’s changed my accept- NVRIYO IOWA OF UNIVERSITY f physicist James Van decision to abandon the ance of theoretical expectations. They IAllen wanted to look back spacecraft].” [theoretical physicists] are a lot of fun, over his career, all the way Best known for his 1958 but you can’t take them too seriously. back to his first experimen- discovery of the Van Allen PT: You’ve been involved in the US tal research as an under- radiation belts surrounding space program since the beginning, graduate at Iowa Wesleyan Earth, Van Allen has spent yet you’ve written that you don’t favor College in 1931, the task much of his life in his native the manned space program. Why? would be daunting. Al- Iowa, including 53 years on VAN ALLEN: I recently wrote an arti- though his papers are con- the faculty at the University cle for Issues in Science and Technol- veniently gathered at the of Iowa. The Van Allen cele- ogy called, “Is Human Space Flight main library of the Univer- bration, which included Obsolete?” I compare the history of sity of Iowa, the school talks by some of his 80 grad- Van Allen human space flight with the history of where Van Allen earned his uate students, several of physics PhD in 1939, the whom have already retired, manned ballooning. I have personal collection stretches across more than was, in Van Allen’s words, “a delicious knowledge of that going back into the 210 feet of shelf space. occasion.” With his birthday festivities 1930s, when it was being advocated as And Van Allen, who was honored by over and the celebration of his 59th a revolutionary new technique for the university in early October on the wedding anniversary with his wife, doing scientific work with human occasion of his 90th birthday, continues Abigail, just past, Van Allen took a crews carried aloft by balloons. That to add to the collection. Five days a deep breath and talked with PHYSICS soon was recognized as a very poor way week, he goes to his office on the top TODAY about his research and the to do it, and that expectation faded floor of a building that bears his name changes he’s seen in physics. away. But unmanned balloons remain and delves into the massive amount of valuable for scientific work. Manned data his Geiger Tube Telescopes gath- PT: For several years you hoped one ballooning has survived only as an ad- ered on their decades-long journeys of the two Pioneer spacecraft would be venturous sport. through the solar system aboard the the first to reach the heliopause, the From the perspective of 2004, I con- Pioneer 10 and 11 spacecraft. The last edge of the Sun’s influence. When the sider that human space flight has had bit of the data came from Pioneer 10 in craft were launched in the early a parallel history and is now best re- February 2003, when NASA finally 1970s, how far away did scientists be- garded as an adventurous sport, ap- shut down communications with the lieve the heliopause was? propriate perhaps to the private sector small spacecraft. “It was about 80 as- VAN ALLEN: There were some pre- but not to governmental support. Cur- tronomical units away,” Van Allen said, liminary indications that the helio- rent human space flight makes minor and detecting its 8-watt signal across pause would be at 5 or 6 astronomi- contributions to scientific knowledge more than 11 billion kilometers of cal units, just beyond the orbit of and virtually no contribution to the space was “terribly demanding. I had Jupiter. That was the prevailing ex- pervasive role of space technology in the only instrument on board still op- pectation at the time we launched Pi- modern life. All of [the] great advances erating so I had a hard time justifying oneer 10. And it’s sort of been like a in science of the Earth and all of the keeping going. So I didn’t kick on [the rabbit on a racetrack. It’s kept ahead planetary exploration have been done

32 December 2004 Physics Today http://www.physicstoday.org