What material and visual means have astrophysicists and cosmologists developed to explain the composition and history of our universe? The emergence of high-precision, big-data, born-digital cosmology in the late-20th century depended upon detecting, interrogating, and making visible the universe’s very first light—the cosmic microwave background (CMB) radiation. This article analyses how, between 1974 and 2013, physicists and space scientists grappled with building interlinked instruments that could engage with the material effects of light to visualize, map, and interpret these invisible primordial messages. Astrophysicists, instrument-builders, and engineers used data collected from instruments on NASA’s COBE and WMAP and ESA’s Planck space probes to produce iconic images mapping the universe’s embryonic structure, theoretically-anchored precision visualizations modeling the evolution of cosmic structure from the big bang to today. This paper argues that creative aesthetic concerns appeared at all stages in these missions, from instrument design to image production to public outreach.
This article explains how teams of cosmologists, astrophysicists, engineers, and instrument-builders, utilized, created, and transformed-at-need sophisticated technologies to detect and make visible with high precision the messages embedded in “the very first light” in the universe, the cosmic microwave background radiation (the CMB). CMB radiation is afterglow energy of the big bang, a relic radiation field permeating the universe—in fact, it “still remains the universe’s dominant form of radiant energy [99 %],” in terms of both energy content and the number of photons (the smallest unit of light energy).1 This essay will explore how these scientists came to visualize the cosmos based on the CMB data, and to produce from that data iconic images modeling cosmic evolution from the big bang to today, images mapping the embryonic structures imprinted on space at the big bang. In a very real sense, the history of the universe is contained in the wavelengths of the CMB across the full sky. Scientists who created these images and maps are fond of saying that this very first light of the universe serves as a time machine to take us back as far as we can observationally reach, all the way back to the hot and dense infant universe postulated by the big bang theory.2
The existence of CMB radiation infusing space was not known (although predicted by some theorists) until 1964 when accidently discovered as a steady excess radio signal from every direction that could neither be eliminated nor come from our galaxy. Omnipresent as part of the static (“white noise”) on pre-digital television sets and across a wide FM radio-frequency band, it would have preserved the properties of a perfect “blackbody”—a body “in equilibrium with itself” so that “no part is warmer or colder than another” and hence reradiates in “a highly characteristic pattern [depicting intensity versus frequency]” that today would have expanded to microwaves of wavelength between 0.4 and 700 millimeters with a temperature estimated from 2.5 to 5 K above absolute 0. Instrumentalists rushed to the tops of high mountains and to Antarctica’s cold, dry, clear summer skies to design, experiment, and measure.3
Beginning in 1974, three space missions—the NASA missions COBE and its successor WMAP and the later European Space Agency (ESA) Planck space probe—grappled with the “material effects” (introduced below) of this very first light of the universe as an essential key for addressing fundamental questions of cosmology. The challenge was to design and develop methods (interlinked instruments) for accurate measurement of CMB properties, and to develop associated methods (instruments) for accessing and analyzing the data. Would the data provide an empirical test of the big bang theory? Would full-sky coverage provide sufficient trustworthy data to determine the properties of the universe and its development? This article analyzes how COBE and WMAP secured that understanding, establishing (in conjunction with much else) numbers estimating the age of the universe at release of its first light and the age of the universe today.
In particular, this paper details how the mission scientists sought to depict the thinking built into each instrument they engineered to yield reliable (meaningful) numbers and, in turn, the thinking within the images they produced to transmit these meanings and findings. It develops the actor-based category of an “iconic image” or “icon” that encapsulates the essence (meanings) within a scientific result—such as the CMB data’s “highly characteristic pattern” of blackbody radiation—with an immediacy and clarity that other scientific images do not. It discusses how their iconic images embed traces of the theoretical and instrumental designs that materialize these meanings, and how the images model and map the embryonic structure and evolution of the universe. My assessments of COBE and of WMAP thus spotlight how their instruments of scientific visualization (in process of being created) and their images (created concurrently as “scientific visualizations” rather than “merely accompanying illustrations”) constitute an evolving “materialization of arguments” in the sense of “materialized epistemology” defined by historian of science M. Norton Wise.4
2 Argument and Structure of the Paper
Amidst contending, often misleading, and evolving theoretical clues and empirical lines of evidence in both fundamental physics and astronomy, and with no “materialized” arguments to guide their research, the pioneering COBE scientists had to envision, evaluate, and perfect a concatenation of new and subtle arguments yet to be materialized. My study shows how they came to visualize and materialize their goals and arguments in a suite of utterly new instruments, and how COBE thereby became “much more than the sum of its parts.”5 COBE’s first goal—to reliably measure the current CMB temperature across the full sky—was a huge theoretical and engineering challenge that was paramount for success. Its second goal—to compare the CMB temperature spectrum to the theorized “blackbody spectrum” predicted by the big bang theory—required precision to a degree previously undreamed of in astrophysics. COBE’s third goal was to discern the presence of tiny fluctuations (anisotropies) in the CMB temperature across the sky due to random density perturbations in the early universe that seeded the growth of cosmic structure (galaxies, galaxy clusters, and superclusters).
In the bold follow-up mission, WMAP’s specially-designed instruments, and its unobstructed view to deep space from a fixed location in the sky, enabled data of greatly enhanced reliability and precision from a thousand-fold more points throughout the full sky. Operating continuously from September 2001 into August 2010 (each year completing two full-sky scans), the WMAP satellite provided a continuing flow of data that the team processed, assessed, and published for public use. The 1-year, 3-year, 5-year, 7-year, and 9-year data and findings were eagerly awaited by the astronomy and physics communities. With the release on 11 February 2003 of the 1-year data and findings based solely on the temperature data (the iconic WMAP map featured in this paper), NASA archived and distributed the data online—made ready for scientists to analyze—via NASA’s new “Legacy Archive for Microwave Background Data Analysis” (LAMBDA), including the data processing, calibration, systematic error analysis, and other critical aspects of the experiment.6
WMAP’s science impact was immediate, extending beyond space science. The findings of the 1-year data, reported in 13 scientific papers in 2003, were declared “Breakthrough of the Year” by Science magazine, noting WMAP’s finding (pie chart) that dark energy makes up 71.4 % of the matter-energy density of the universe today, with 24 % dark matter, 4.6 % ordinary (baryonic) matter, and 0.4 % photons. The release of 3-year data and findings in March 2006 incorporated the much weaker polarization signals, calibrated and analyzed for systematic error in archived data files. Findings included evaluations of specific inflation scenarios, analysis of the “angular spectrum” showing relative brightness-versus-size of the fluctuations in the WMAP map, and a visualization narrating “The Evolution of the Universe” (also featured below).
The 2008 and 2010 reports, with unprecedented precision, updated values for the present universe (more dark energy and less dark matter and baryonic matter) and produced a pie-chart “census” of the universe at 380,000 years old, showing dark energy as an imperceptible line, 5 % photons, 12 % baryonic matter, 63 % dark matter, and a 10 % slice of neutrinos that permeate today’s dark-energy-expanded space, awaiting detection. “WMAP results were among the most-cited scientific papers in the world across all scientific disciplines, not just in physics and astronomy,” in 2003, 2007, 2009, and again in 2011 when “WMAP captured first, second, and third spots in the rankings in a single year—a science trifecta.”7
With their ever-advancing multi-textured flow of observational data, analysis, and “scientific visualizations”—thoroughly cross-checked and secured as trustworthy and compelling by intensive scientific scrutiny—COBE and WMAP had provided definitive “breakthroughs” in fundamental physics that anchored a “concordance” vision of cosmic structure and evolution impacting all of physics.
Today’s standard inflationary model of big-bang cosmology posits that in the trillionth-of-a-trillionth of a second after the big bang, the trillion-trillion-fold expansion of space during inflation drew any initial random quantum fluctuations making up the infant universe into gravitational potential wells in the extremely hot dense plasma.8 Radiation (light photons) and matter were so tightly coupled in this ionized plasma that light could not travel. But as the primordial universe cooled and stretched, radiation and matter gradually decoupled, ultimately leading to a condition such that, for the very first time, when the universe was about 380,000 years old, photons were able to travel freely through space, “preserving a ‘snapshot’ of the Universe at the time of decoupling” materialized in the WMAP map (as we will see below).9 Over the next approximately 13.77 billion years, continued cosmic cooling and expansion has stretched these light waves to the microwave part of the electromagnetic spectrum, which is the CMB radiation we detect today.
My case study concurs fully with the conclusion of a broad-based analytical assessment of “the technical image” in history that “visualization is in itself a technology … an interpretive intervention … [having] productive power,” and also with its methodological framework that “compels the observer [of any visualization to go] beyond its phenomenological appearance in order to comprehend its modes of operation and specific functions.”10 Work in the sociology of science can likewise expose the generative power of visualizations in opening up new visions and setting in motion further scientific quests. Throughout, one cannot ignore the technology of instrumentation that establishes the subtleties of the messages and their materialized visualization. As Sebastian Grevsmühl argues, “visual analysis necessitates paying close attention to the instrumentation and the tools involved in the elaboration of scientific phenomena and knowledge.”11
As used here, an “instrument” is an investigative tool (existing or newly created) with a built-in ability to serve a particular function such that the “purpose” for its use is inherent in the nature of the instrument. Study of the CMB evolved amidst huge technological advances and the “digitization” of the sky whereby the telescope “merged with the computer, the software program, and the database into a hybrid instrument.”12 COBE and WMAP thrived as “purpose” drove innovation of ever-new “instruments” to serve specific needs—utilizing at will select regions of the spectrum of light as filter, engaging nuances of mathematics, creating algorithms, fueling and mining data pipelines, and so much more. In my interpretive historical study of these missions to visualize and comprehend the cosmic first light, instrumentation and visualization are entangled. Moreover, I argue, they cannot be separated from the “aesthetic sense” that nurtures this entanglement, propels scientific advance, and secures relevance and impact.
My paper first explains (in two brief sections) what I mean by visualization, instrumentation, and the aesthetics of understanding, and how these meanings enter into my analysis. Then, drawing upon my interviews with the project leaders, two sections analyze the goals, challenges, innovations, findings, and visualizations of the COBE and WMAP missions that successfully measured and mapped the CMB, opening new windows on the universe. The Planck mission likewise engaged myriad new data and tensions arising from studies of the near universe of energetic galaxies. Concluding comments emphasize how my paper generalizes aesthetic materialization from these CMB studies to the history of science more broadly.
3 Visualization and Instrumentation: Working through the “Material Effects of Light”
In telling the story of how teams of scientists were able to “visualize” the cosmos with its first light, this article builds upon interpretative perspectives on visualization and aesthetics that accompanied the advance of science.13 By visualization (which attaches to the meaning of aesthetics used here) I mean not merely metaphorically visualizing with the mind’s eye, nor merely obtaining the iconic images of the cosmic first light. Visualizing also means active ways of making the mind’s hard-won clarity of understanding become visible to the eye within images, and how the making of both involves light in a complex concatenation of cognitive and material processes.
According to historian Raz Chen-Morris, this process was recognized by Johannes Kepler in his optical investigations which served to anchor his broader efforts to “rethink the relationship between mathematical procedures, instruments of observation, and the human mind.”14 Kepler repeatedly emphasized that knowledge about the “invisible” must come from working through the “material effects of light,” proclaiming that “the study of the refraction of light [is] the kernel of [the] new optics.”15 Kepler’s insight here was profound: the physical realities of the cosmos can only be described, measured, and understood via scientifically-conceived instruments of observation based on the material effects of light. X-rays are so energetic that X-ray telescopes require mirrors “made of material that will reflect an X-ray photon and … oriented such that the X-rays hit the mirror at the [mathematically determined] grazing incidence.”16 Millimeter wave receivers likewise are necessarily part of complex instrument systems. Kepler’s insight is crucial to all of observational astrophysics, in particular to CMB research and aesthetics, from instrumentation to interpretation and visualization.
4 Aesthetics and Visualization of the Cosmos
My study provides historical evidence of how each of these CMB missions—driven by aesthetic purpose and need—devised various ways to use properties of light as “instruments” for isolating, detecting, assessing, and/or mapping the messages in the CMB. Intertwined concerns engaging aesthetics, geometry, mathematical reasoning, and the physical world at its most distant and sublime undergird such technological efforts to interrogate and envision the universe’s first light, driving the quest for cosmic understanding.17
For millennia, our only source of knowledge about the cosmos came from visible light from the stars, while philosophy, theology, and ever-advancing mathematical and physical sciences filled in conceptual, theoretical, or mechanical details. Novel nineteenth-century instrumentation opened up the spectrum of visible light to astronomers, propelling construction of ever-bigger optical telescopes, while twentieth-century innovations gave access to non-visible regions of the full spectrum of light. Whether using optical or non-optical telescopes, spectroscopy or interferometry, light is intrinsically involved in both the message (the data observed) and the various instruments used to detect, explore, and interpret that message. Regarding each of these functions, mathematics necessarily enters as an “instrument” without which the aesthetic purpose embedded within the “technological instruments” cannot be realized, nor the observations attain precision of meaning.
The twofold characterization of mathematics itself as an instrument, and mathematics serving an aesthetic purpose, was made by the French mathematician Henri Poincaré, who was widely esteemed for the aesthetic sensitivities of his thinking in his mathematics and public essays. Addressing the first International Congress of Mathematicians in 1897, Poincaré claimed that mathematics has a “triple aim.” It is not enough that mathematics “furnish an instrument for the study of nature,” an instrument (such as his new methods of celestial mechanics) that serves to illuminate both what lies ahead to be discerned and the way to proceed. Mathematics, he insisted, “must also have a philosophical aim, and I dare maintain, an aesthetic purpose,” for it “must aid the philosopher [and physicist] to fathom the notions of number, of space, of time.” Only mathematics can “express relations so delicate, so rich, and so precise.”18 From Ptolemy’s Almagest (Mathematical Treatise) to Newton’s Principia Mathematica and beyond, the notions of number, size, place, time, and motion were considered an “order of being” situated between “theoretical philosophy” and physics, namely, within “mathematics … [where] they can be conceived of both with and without the aid of the senses.”19 The very effort to probe these foundational notions of experience, Poincaré argued, is intrinsically aesthetic, a personal and communal intellectual fathoming, and it is open to all.20
In essays addressing a wide public, Poincaré spoke of intelligent beings in a fictive universe whose physiological experiences undergird the mathematics and physics of their world, showing how our intuited notions of space, time, and distance could mislead us. By developing intuitions of a “topological” (spatial-relational) nature “exempt from all idea of measurement” (so that its theorems “would remain true if the figures were copied by an inexpert draftsman who should grossly change all the proportions and replace the straights by lines more or less sinuous”), new vistas and entire universes of understanding are opened to us.21 Might the shape of our universe be hyperbolic or closed (possibilities confronting the “laser-slinging slug” we meet below) rather than flat? The new topological thinking and such mathematically possible worlds dazzled literary and artistic communities and continued to drive intellectual fathoming within physics and cosmology.
As a broad cultural trope, “aesthetics” appeals to the sense of beauty, symmetry, or simplicity, but in the ideational realm the term attaches to the experience of enlightenment, of finally coming to grasp something hidden, subtle, highly valued, and long pursued. Here I consider aesthetics emergent within the practice of science as the scientist seeks understanding at boundaries of the unknown. In the late nineteenth century—amidst great scientific interest in optical illusions and how the mind is misled by what it sees—Ernst Mach attributed “the soothing, enlightening, and aesthetic moment” that accompanies scientific resolution of a conundrum to the “economy of communication and conception” within that resolution, linking the aesthetics of physical laws to the physiological basis for visual aesthetics.22 By the twentieth century, new forms of radiation and evolving theories of light questioned a narrow understanding of the “aesthetic moment,” even as general relativity and quantum mechanics established as the epitome of a “good” physical theory the simplicity of physical principle and symmetry unchanged under transformation. Einstein’s general-relativistic cosmological considerations revealed, in its essence and impacts, that aesthetics encompasses much more than that.
I argue that aesthetics attaches to a searching aimed to illuminate clearly and reliably, a seeking of analogical or iconic means to enable oneself and others to grasp the essence of a difficult concept—suddenly to fully understand its meaning, secret, inevitability, and power, namely, “how it sheds light around itself, like Lichtung—a clearing in the wood.”23 Be it visual, textual, analogical, mechanical, or very specific (such as the integral sign in calculus, or demonstrating the “right-hand rule” in electro-magnetism), an aesthetic icon must be precise and tangible, and yet have a certain generality of application.24 An aesthetic icon (materialization of argument as instrument or image) is something long-sought that is finally found, enthusiastically shared, treasured for its striking successes, and repeatedly mined for its envisioned promises.
5 COBE: Thinking in the Instruments
The CMB was discovered in 1964 as excess signal received by the great horn radio antennae at Bell Labs in Holmdel, New Jersey, which the radio astronomers Arno Penzias and Robert Wilson could neither eliminate nor explain.25 Their detection “scooped” a team at nearby Princeton University led by astrophysicist Robert Dicke, his “theoretical right-hand man” Jim Peebles, his chief experimentalist David Wilkinson, and other colleagues including Peter G. Roll and Bruce Partridge.26 Explaining the persistent excess signal as a record of the current temperature of the hypothesized CMB, the Princeton team corroborated the detection of the CMB and further refined the temperature measurements using ground- and balloon-based (high-atmosphere) instruments. Throughout the 1960s, Dicke’s team conducted experiments to detect the CMB and measure its possible anisotropies.27
Wilkinson recalled that “those few of us who were working in the early days (of string and sealing wax cosmology) have more appreciation of how hard it was.”28 While working at the MIT Radiation Lab during World War II, Dicke invented two vital pieces of CMB detection technology—the Dicke switch and the Dicke radiometer (discussed below)—which still serve as the main instrumental means for detecting the CMB on the ground, on balloons, and on spacecraft. In the 1970s, NASA funded high-altitude experiments using the Dicke radiometer, including the Princeton team’s balloon-load CMB experiments.29
Work on radio astronomy at Queen Mary’s College (London) and Cavendish Laboratory (Cambridge), and independent balloon studies by John Mather, Paul Richards, and David Woody at the University of Berkeley, accelerated engineering advances in interferometry in search of anisotropies, with Woody finally obtaining “good data” that found an anisotropy due to the motion of the galaxy with respect to the universe.30 Observational cosmologists at Lawrence Berkeley Laboratory (Richard Muller, George Smoot, and Marc Gorenstein) carried out U-2 plane experiments and also found that anisotropy.31 Each study confirmed that the CMB is nearly uniform in temperature in all directions of the sky, and each enabled estimations of the range of precision required in future efforts to detect the tiny fluctuations in temperature.
A turning point in CMB research occurred in 1974 when NASA invited proposals for science missions on Delta rockets. John Mather, at NASA’s Goddard Institute in New York after completing his PhD at Berkeley, suggested that his thesis experiment designed to examine the CMB would have worked much better in space. Only a space-based mission could fully avoid the interference of electromagnetic emissions from earth’s atmosphere.
Three independent proposals for a space-based CMB mission were accepted by NASA and combined into a single new mission, a satellite named COBE (cosmic Background Explorer), headed by Mather. Fifteen years later, on 18 November 1989, the COBE spacecraft was launched into low earth orbit (the sole launch of the Delta 5000 series) from Vandenberg Air Force Base, remaining in orbit until 23 December 1993.
Mather recognized the huge challenges ahead: “COBE would be exploring uncharted scientific territory. Its instruments were unlike any ever built before.”32 The overriding demand was to ensure that the data were reliable, that the radiation collected and studied would be fossil CMB, not foreground or instrument emissions. Keeping reliability at the forefront of the team’s agenda, Rainer (Rai) Weiss, MIT professor and Chair of the COBE Science Working Group, insisted on continuing interactions between the science team and instrument builders, and on continuing testing and retesting. Each instrument, and the positioning and functioning of the satellite, had to correctly materialize the theorists’ arguments and do only what their arguments demand: together they ensure that the data assessed comes only from the fossil CMB.
COBE consisted of three instruments with complementary goals—FIRAS (Far-InfraRed Absolute Spectrophotometer), DMR (Differential Microwave Radiometer), and DIRBE (Diffuse InfraRed Background Experiment)—to enable removal of all non-primary data. Each instrument was carefully tuned to detect particular wavelengths known to be produced from closer sources: radiation emitted by the accelerating charged particles in electric and magnetic fields around earth, within the solar system, and from the Milky Way, and even the electromagnetic signatures of the instruments themselves. Since sparks from any source could instantly destroy any of the sensitive instruments, engineers used “electrically conductive paint” and “ground[ed] the superinsulation to the spacecraft’s metal structure to eliminate internal sparking.”33 To discern their requisite wavelengths with utmost precision, the FIRAS and DIRBE instruments had to be cooled to an extremely low temperature throughout the first months of data collection, making COBE one of the first NASA missions requiring cryogenic cooling technology.
The FIRAS instrument used interferometry (interference of the incoming infrared waves) to measure the difference between the spectrum of the CMB radiation itself, and the spectrum of an internal blackbody at the temperature of 2.7 K, the current temperature of the CMB. Mather and his team designed FIRAS to be an ideal null differential instrument, to detect any deviations of the CMB from the “ideal blackbody.” Even small deviations from the ideal blackbody in the CMB spectrum would require revision of the hot big bang theory. FIRAS determined that the CMB temperature is 2.725 +/- 0.001 K and “limited any deviation from a blackbody to fifty parts-per-million of the peak brightness.”
When Mather presented the perfect blackbody graph of the first FIRAS results (Fig. 1) at the January 1990 American Astronomical Society meeting, the whole audience was stunned, spontaneously giving a standing ovation with persistent applause.34 Wilkinson explained this aesthetic moment as their suddenly seeing experimental proof of a long-held belief. “There was expectation.” The audience of scientists knew what COBE had attempted, they didn’t know how the apparatus could succeed, and “then all of a sudden there it was—clear as a bell. The universe’s big bang. No doubt about it.”35 Mather assessed the audience’s response as reflecting the aesthetics of the instrument’s Dicke differential design that enabled success: “They thought it was a beautiful experiment, and it was.”36 This image, the graph recording the FIRAS data, demonstrated that the CMB had the distinctly blackbody spectrum characteristic of relaxation to thermal equilibrium as predicted by theory—that is, that the universe had to have expanded and cooled from a hot dense state—and was seen as the ultimate confirmation of the big bang theory. Moreover, the perfection of the FIRAS blackbody spectrum graph marked cosmology as a precision science.37 Encapsulating the clarity of aesthetic purpose carried through the instrument’s design to its output, this icon at a glance reveals the underlying physics.
The COBE DMR instrument, designed to measure the anisotropy, consisted of multiple differential microwave radiometers. In the heart of each radiometer was a “Dicke switch” that repeatedly compared the incoming radiation between the two antennas, enabling a precision comparison of one direction with another. In receiving the Shaw Prize in Astronomy in 2010, Charles Bennett, the Deputy Principle Investigator of DMR on site at NASA’s Goddard Space Flight Center (GSFC), said that the effort “to improve the sensitivity of the DMR radiometers by re-working its mixers … made a crucial difference in the discovery of the CMB temperature variations across the sky (the ‘anisotropy’).”38 Of the four planned DMR wavelength channels, the lowest frequency band was tested by balloon studies carried out by Princeton, aided by MIT and NASA’s Jet Propulsion Lab (JPL). Bennett realized that the two highest frequency bands could be made greatly more sensitive if the receivers were kept at a very low temperature (140 K). Precision instrument builders at the National Radio Astronomy Observatory (NRAO) were commissioned to modify the receivers according to exacting specifications, producing also an experienced group of practitioners whose skills would be called upon again in the follow-up mission, WMAP.
Aided by global information derived mainly from the COBE instruments, the various troublesome foreground emissions were fully removed during data analysis, yielding the primary DMR data. Bennett led the DMR data analysis effort at Goddard, wrote one of the four discovery papers of the anisotropy, and headed the continued analysis of the COBE DMR data that gave major results in 1994 and 1996. Ned Wright developed the scheme for making the map, created the mathematical algorithm for producing it, and led analysis of the output that made the data visualizable. The images produced from DMR data gave the first glimpses of the anisotropies of the early universe—the reality that the embryonic universe had slight differences in density causing slight changes in temperature in the CMB, seeds of structure in the universe.
Wilkinson explained that “it was exceedingly important to finally measure the level of the anisotropies because the theorists have all kinds of reasons for believing it had to be there,” the main reasons being that “you can’t start out with a perfectly smooth matter distribution way back there and end up 14 billion years later with what we see in the sky. These were hard [firm] calculations [by the theorists].”39 But no one had detected anisotropies before and no one knew what they would look like, what kind of output to expect that could make the scientists believe that the output truly represented the CMB anisotropies. The first “detection” of the anisotropy was made by Ned Wright from early data inputs into his program that he reported to his project colleagues. Wright followed the Science Working Group’s contract and caution, first processing more data to confirm the DMR findings as truly anisotropy, then postponing publication until their rigorous checks were completed.40
As Bennett recalled, “it was a huge issue to see that the experiment is right,” to assess whether the output is truly from the CMB or whether it could be from anything else—from the sun, the earth’s orbit, a hot signal getting into the instrument, or a temperature change on the satellite. Trying to track things down was difficult: “We worked a long time to convince ourselves on the believability of it.” Everyone had to be on board for each kind of analysis. Given the importance of the question and the stakes if they were wrong, they would not accept the results as believable until they had dug in, looked at the maps and analyzed the maps—until they were fully convinced that “the signal had to be true [CMB anisotropy]” because “it could not be from any of those systematic effects.” They would not make the announcement until they had looked everywhere: “We took the time to get it right.”41 Just when the analysis was set for team publication, George Smoot, the DMR Principal Investigator, made a surprise public announcement of the DMR findings, also publishing an account of his life-long efforts to amass and interpret the various clues that light offers to the scientist about the origins and structure of the universe.42
As Principle Investigators of COBE’s FIRAS and DMR instruments, John Mather and George Smoot won the 2006 Nobel Prize in Physics for the team’s “discovery of the black body form and anisotropy” of the CMB. The COBE team—experimentalists, instrumentalists, engineers, data analysts—pressed for a new mission to detect and map these temperature fluctuations with far greater precision.
6 WMAP: Opening New Windows on the Universe
The new mission, MAP (Microwave Anisotropy Probe), was later renamed WMAP in honor of the late David Wilkinson who was vital to the project’s development from inception through launch (receiving the first results showing anisotropy before his death in September 2002). The WMAP instrument was a product of NASA’s GSFC in partnership with Princeton University, continuing along some of the same lines as COBE. As Principle Investigator “with full budget and authority to direct all aspects of the mission,” Charles Bennett “involved the [small personally-selected] Science Team heavily in the hands-on design and development process.” From Princeton, Norm Jarosik, Lyman Page, and Dave Wilkinson and others “provided instrument design input,” and one of Wilkinson’s recent PhD students, Edward Wollack, worked with colleagues at NRAO to design and build the highly sensitive amplifiers required for the mission.43 From proposal in the mid-1990s, to satellite launch on a Delta II rocket from Cape Canaveral on 30 June 2001, to release of the first-year data and images in 2003, the WMAP project was recognized as a landmark managerial as well as scientific success.
Well before launch, the science team developed itemized goals focused on carefully designing the instruments and spacecraft, with continual monitoring of all aspects of the evolving design to attain the degree of reliability needed for the data to give trusted information. Polarization data was not a requirement of the mission but was included even though they were not ready to analyze it—among their first stretch goals for the extended mission approved by NASA after release of the first year’s data results. Meanwhile, in April 2000, an international team of scientists, using 40-times more sensitive balloon-borne detectors than ever used, reported very clear images of the ripples in the sky. With its unique design, instruments and images, WMAP would take theoretical understanding and visualization of the universe to an entirely new level, opening new questions and paths.
Awaiting results, the WMAP Science Team sought visual means to explain the mission design and expected findings to the public and media, creating a set of “Fun Fact” postcards in 2002 with graphic designer Britt Griswold.44 During the first month after launch, the spacecraft carried out phasing loops around earth; then, using a lunar gravity-assisted boost, it traveled for two months to a special location 1.5 million kilometers away called the Sun-Earth Lagrange Point L2 (a point in space where the gravitational forces of the Sun and Earth equal the opposing force required for the spacecraft to maintain its position)—the first spacecraft to remain orbiting at L2 (not just pass L2 on a flyby).45 As NASA postcard “Greetings from L2” (Fig. 2) depicts, because L2 remains in Earth’s “shadow” as it revolves around the Sun, the WMAP spacecraft would continuously be in an “exceptionally stable environment” at nearly constant temperature and “unobstructed view,” enabling far greater precision in CMB temperature measurements over the full sky.46
Another WMAP postcard (“Microwaves in Space?”), humorously picturing a winged microwave oven in space, explains how this “left-over light from the big bang” became “stretched out by the incredible expansion of the universe,” and how measurements of “this ‘fossil’ light from the distant past” will enable scientists to learn about the age and contents of the universe.47 A third postcard (“Does the universe have a fingerprint?”) analogizes the infant universe with a uniquely identifiable fingerprint, examined through a magnifying glass by a detective in a deerstalker hat. Supercomputer simulations would compare the statistical patterns in the CMB collected by the WMAP mission with patterns for “cosmic suspects” of differing cosmic ages, content, geometry, and futures. The parameter values giving the best statistical fit to the observed data (that matches the “fingerprint”) will give the proportions (census) of dark energy, dark matter, and baryonic matter in the universe.48
One of those parameters (geometry) is featured in a fourth WMAP postcard asking, “Should this laser slinging slug have fired his weapon?” (Fig. 3), and answering, “it depends.” A laser-slinging slug living in a tiny universe would have no reason not to fire his laser if his universe is flat, or if his universe is open (a saddle-shaped “hyperbolic universe”); but the laser-slinging slug would eventually have an unpleasant surprise if his universe is closed (a so-called “spherical universe”), having shot itself in the back.49 The Team used the classic convention of picturing the possible curvatures (“geometries”) of our three-dimensional space as the curvatures of two-dimensional surfaces (where the two-dimensional slug lives).
The postcards were effective outreach highly valued by the cosmological community because they expressed to the public the particular challenges and critical importance of the information cosmologists were seeking. Their supply was quickly depleted by requests from educators. Such images captured crucial aspects of the aesthetics infusing this long, intense endeavor—the need to know with exactness all that is essential, the need for the instruments to yield precise accurate data with which to establish reliable findings. They “materialized” the aesthetics that fueled and secured this quest in the ever-present face of possible design failures, instrument damage, or various contingencies that could threaten success.
All who participated in designing and engineering the instruments and satellite had ensured the reliability of these tiny temperature fluctuations, and all members of the Science Team—including Bennett, Ned Wright, Gary Hinshaw, and David Spergel—contributed to the mission’s ability to identify from these anisotropies the composition of the present universe. Wright explained the scheme for making the map from sky-scanning data and shared his algorithm for getting “pointing data” indicating where the instrument was pointing in the sky; Goddard software engineers and contractors sped up the process. COBE and WMAP software were coded in the Interactive Data Language (IDL) and in FORTRAN.50 Most of the COBE files and the WMAP data releases were in the Flexible Image Transport System (FITS). NASA’s GSFC was on the forefront of this transformation into an open-access, international, institution-independent, big-data digital era of astronomical research.51
The iconic WMAP image of the all-sky map of CMB temperature anisotropies (Fig. 4)—the 2003 “Breakthrough of the Year”—was the “scientific visualization” of the mission’s multi-textured “materialization of arguments,” 70 times more sensitive than the DMR data. The WMAP map is, Bennett explained, “largely a map of the sound wave pattern at the time of decoupling of photons and matter.” The sound wave oscillation occurs from a “tug-of-war between gravitational attraction of dark matter into potential wells and the restoring force of radiation pressure [which] sets up an oscillation in the photon-baryon fluid” that continues until precipitously released at “decoupling” when the first light “free-streams” across the Universe.52 These slight fluctuations in CMB temperature across the full sky are represented by “hot” (red) and “cold” (blue) spots on the map. By graphing the relative brightness of the spots versus the size of the spots (the CMB angular spectrum), WMAP data established a characteristic “co-moving length” to serve as a “cosmological yardstick” (that stretched with cosmic expansion) for calculating the universe’s current expansion rate (Hubble’s constant) based on quantum and particle physics and assumptions about dark matter and dark energy in the early universe.
The two NASA CMB space missions entered popular culture with their widest audience yet when one of the promotional materials—an inflatable beach ball with the WMAP all-sky map projected on the surface—ended up as a permanent fixture on the set of “The Big Bang Theory” television show (even signed by COBE’s John Mather).53 MIT physicist Max Tegmark (who was not on the WMAP Team) “adorns” his office with the “cosmic beach ball”: “I call it my ‘universe,’ because it’s the iconic image of what bounds everything we can in principle observe.”54
The WMAP poster, postcards, and Figure 5 were designed and made by the WMAP Science Team with Goddard graphics specialist and website designer Britt Griswold. On a 2018 panel (“Visualizing Science: The Art of Communicating Science”), Griswold said that “[scientists] don’t communicate in the way you need so you have to go hunting for it. You go back and forth and back and forth, and sometimes you have to ‘coach’ them on how to say what they want to say.”55 Griswold worked with the team to formulate thoughts about graphic imaging, corrected some of their sketched-out versions, and helped the team explain in an image what they wanted to communicate. Bennett and the team located aesthetics in the move from an idea pictured in a scientist’s head to a shared understanding that becomes engrained in the image, that makes it iconic.56
Encompassing the cosmological message of the WMAP mission, the image visualizing the “Evolution of the Universe” (Fig. 5) conceptualizes WMAP’s challenges and analytical findings as materialized messages intrinsic to the image. We see the WMAP satellite at work in the vastness of space (note the galaxies) looking into the cosmic story its observations are recording. The universe (space itself) is imaged as a vertical slice, expanding as it ages, widening more as it approaches the “time slice” of our present-day, galaxy-filled, space teeming with “foreground” emissions that had to be avoided for the satellite instruments to record only the earliest light. The instruments thereby paint the iconic “WMAP map” (Fig. 4) which appears at a “time slice” many billions of years back—the “time of last scattering” when the universe was about 380,000 years old and light was finally able to travel freely in space as the CMB radiation the satellite is recording. The “WMAP map” makes visible this cosmic light: anisotropies in the patterns (difference in colors) reflect areas of greater and lesser density that are seeds of structure “measurable” in the “first light” photons that 13.7 billion years later comprise WMAP’s observations from its position at L2.
This “history of the universe” visualization, which tracks expanding space through slices of time, places a linear narrative of the evolution of structure onto the static “WMAP map” infused with meaning. It does epistemic work for the viewer that marks its particular utility for both experts and learners. This visualization was the most emailed image on the internet the day it was released and remains among the most reproduced cosmological images. It is an iconic image of the cosmic evolution that the WMAP instruments recorded in the iconic WMAP map of fluctuations in temperature in the CMB.57
7 Planck and WMAP in Dialogue: New Data and New Tensions
Bennett emphasized the differential nature of the detections by COBE DMR and WMAP: absolute measurements could have given greater precision but far less reliability.58 In 1998, during construction of the satellite, the Science Team designed a MAP Poster for the media (with Griswold’s artistic renderings) explaining how the instrument design anchored the WMAP mission goal of “measuring cosmic history … charting cosmic destiny.” WMAP’s back-to-back telescope design measures “the difference between the brightness seen in one telescope with that seen in the other, so the contaminating emission from the two telescopes approximately cancels in such a measurement.”59 Also WMAP would use five different frequencies within the microwave band (rather than COBE’s three) to help distinguish the foreground Galactic microwave emission from the “cosmic emission” (CMB signal).
In contrast, the Planck mission, launched in 2009 by the ESA and NASA JPL, used absolute microwave radiometers with the explicit goal of attaining greater precision, and nine different frequency channels. Some initial apparent discrepancies between the WMAP data and the Planck data were due to the Planck team’s choice to use non-differential instruments.60 The Planck team also used a different, more muted, color scheme to distinguish their all-sky maps (Fig. 6) from WMAP maps. As “analytical graphics,” might Planck’s greater precision (more dots) suggest that its results are more reliable than the WMAP?61 Might viewers of these images experience disparately the “great physiological difference between the bodily response to blue-green (which induces a feeling of coldness) and the response to red-orange (which produces the sensation of warmth)” identified by Lorraine Daston and Peter Galison in assessing historical norms of objectivity in scientific representation?62 Issues of subjectivity arise here.
WMAP’s map of the hot and cold spots has an aesthetic and sensory immediacy, perhaps a psychological reaction to the boldness of the colors by which one reads the map’s meaning. Both WMAP’s and Planck’s use of red-orange for warmer temperatures and blue-green for cooler temperatures match the bodily intuition of the “temperature” sensation these colors produce. This color/warmth bodily intuition is opposite to the astronomical phenomena of red-shifting (longer wavelengths, cooler light) versus blue-shifting (shorter wavelengths, warmer light). Bennett noted that early physics involved intense gravitational and energetic processes with shifting temperature effects that dominated expansion effects, so color/temperature choice was a non-issue. He chose blue and red for their vivid contrast.63
Regarding the scientific messages encoded in the CMB maps, most scientists think that “some form of ‘new physics’ will be needed to solve the mystery” of a 9 % discrepancy between the “predicted” value for the Hubble constant (today’s expansion rate) “calculated” from the “cosmological yardstick” obtained in the WMAP and Planck studies of the “ancient” universe, versus the much higher value of the Hubble constant obtained in the calculations based on “distance-ladder and supernovae observations” of the “modern” universe (and supported by increasingly precise observations from the Hubble Space Telescope).64 This is a testament to how far cosmology has come in precision measuring. While earlier debates about expansion rate and various cosmological parameters stressed potentially problematic data, today the discrepancy is seen more likely an issue of interpretation.
8 Concluding Thoughts
Throughout the COBE, WMAP, and Planck missions, the overriding issue confronting instrument builders, engineers, and data analysts, was negotiating the subtle ways that matter and light interact and impact the reliability of their data. They had to materialize their thinking into ultrasensitive instruments propelled into space. In these evolving missions, cosmology was becoming an experimental science able to provide precision observations of the ancient universe and its history for theoretical interpretation and advance. This article has detailed the prodigious efforts to discern and command the material relations of light to ensure that their data was only CMB measures; they engineered the instruments to this end. We see in each stage of these missions—designing the experiments, constructing the instruments, visualizing science for public consumption—the role of aesthetics as a coming-into-understanding, as building new knowledge incrementally, as ground-work opening paths to new facets of knowledge.
This paper developed the notion of “aesthetics” very differently than as used in the study of art.65 The word “aesthetics” derives from the ancient Greek words “sense perception” and “to perceive,” and “perceive” itself comes from the Latin “to seize or understand.” This iteration of “sensation” and “perception” reflects the human experience of questioning and pursuing until coming to understand. The words of the historical actors in this paper—from Poincaré to the WMAP team—convey insight into the creative practice of the exact sciences.66 Drawing upon their language and imagery, I have sought to convey the lived experience of practitioners as they fuel the aesthetic process of recognizing a scientific conundrum, of realizing the material effects of light within their instruments of observation, and finally of producing iconic images that portray the long-sought and highly-valued result (a fuller understanding) that is shared with others. This process is not unique to CMB research. By tracing the sources and contours of such creative aesthetic experiences in other scientific endeavors, the historian may glean deeper insight into the intentions, goals, and practices of the scientists they are studying.
In the case of CMB research, we have seen that the scientists built the sensitivity of their instrument into its design, from its differential nature to the amplifiers tuned to access specific regions of the electromagnetic spectrum, from the types of materials used, to the instrument’s temperature. For experimentalists, aesthetics involves experiencing how the instrument or experiment becomes the simplest to do the job. The creative aesthetic move is to ensure that the instrumental design enables the experiment to yield a result that the mission team can agree upon as consistent, credible, and intelligible.
All high-precision experiments aspire to this last stage: all are challenged, during instrument design and data collection or processing, to materialize their thinking into meaningful output. Particularly challenging is achieving credibility beyond the experimental team. This study suggests ways in which historians of science can engage the aesthetics of these quests. Aesthetics is not an end result, but a process of creation from thought materialized within an instrument’s design, through the mediated production of a meaningful image, to a shared understanding engrained in the image.
John C. Mather and John Boslough, The Very First Light: The True Inside Story of the Scientific Journey Back to the Dawn of the Universe, rev. ed. (1st ed. 1996; New York: Basic Books, 2008), 138, 106.
See the video interviews of five leaders (identified below) of the 27-member WMAP Science Team upon the Team’s receipt of the 2018 Breakthrough Prize in Fundamental Physics,
Mather and Boslough, The Very First Light, 40–41, 106.
M. Norton Wise, “Making Visible,” Isis 97 (2006): 75. Sebastian Vincent Grevsmühl, “Images, Imagination and the Global Environment,” Geo: Geography and the Environment 3 (2016): 9.
Charles Bennett, one-day Oral History Interview with the author, Johns Hopkins University, May 23, 2018.
Mather and Boslough, The Very First Light, 141. Alan Guth, The Inflationary Universe: The Quest for a New Theory of Cosmic Origins (Boston: Addison-Wesley/Perseus Books, 1997).
Mauro D’Onofrio and Carlo Burigana, eds., Questions of Modern Cosmology: Galileo’s Legacy (New York: Springer, 2009), 73.
Peter N. Miller, “Forward,” in The Technical Image: A History of Styles in Scientific Inquiry, ed. Hors Bredekamp, Vera Dunkel, and Birgit Schneider (Chicago and London: University of Chicago Press, 2015), ix; and the book’s Introduction by the editors, “The Image—A Cultural Technology: A Research Program for a Critical Analysis of Images,” 2.
Grevsmühl, “Images, Imagination and the Global Environment,” 9.
W. Patrick McCray, “How Astronomers Digitized the Sky,” Technology and Culture 55 (2014): 937.
See, for example, Samuel Y. Edgerton, The Mirror, the Window, and the Telescope: How Renaissance Linear Perspective Changed Our Vision of the Universe (Ithaca: Cornell University Press, 2009).
Raz Chen-Morris, Measuring Shadows: Kepler’s Optics of Invisibility (University Park: Penn State University Press, 2016), 7.
Elizabeth A. Kessler, Picturing the Cosmos: Hubble Space Telescope Images and the Astronomical Sublime (Minneapolis: University of Minnesota Press, 2012), 5.
Henri Poincaré, “Sur les rapports de l’ analyse pure et de la physique mathématique,” Acta Mathematica 21 (1897): 331–341; repr. as “Analysis and Physics,” in The Value of Science, trans. George Bruce Halsted (New York: The Science Press, 1907), 75–76.
Ptolemy, Ptolemy’s Almagest, translated and annotated by G.J. Toomer, with a Foreword by Owen Gingerich (Princeton: Princeton University Press, 1998), 36.
Connemara Doran, “Poincaré’s Mathematical Creations in Search of the ‘true relations of things,’ ” in Ether and Modernity: The Recalcitrance of an Epistemic Object in the Early Twentieth Century, ed. Jaume Navarro (Oxford: Oxford University Press, 2018), 45–66.
Henri Poincaré, “L’ espace et ses trois dimensions,” Revue de métaphysique et de morale 2 (1903): 281–301; repr. as “The Notion of Space,” in Poincaré, The Value of Science, 40–41.
Ernst Mach, Die Mechanik in ihrer Entwickelung historisch-kritisch dargestellt (Leipzig: F.A. Brockhaus, 1883), 5. Quoted in Richard Staley, “Ether and Aesthetics in the Dialogue between Relativists and Their Critics in the Late Nineteenth and Early Twentieth Centuries,” in Navarro, Ether and Modernity, 181.
Gian-Carlo Rota, “The Phenomenology of Mathematical Beauty,” in The Visual Mind II, ed. Michele Emmer (Cambridge: The MIT Press, 2005), 12.
On symmetry in physics and representational icons, see Simon L. Altmann, Icons and Symmetries (Oxford: Oxford University Press, 1992). I thank Dr. Edward J. Wollack for this reference.
Penzias and Wilson were awarded the 1978 Nobel Prize in Physics for their discovery of CMB radiation.
Letter from Dicke to Prof. Frank R. Tangherlini (Department of Physics, George Washington University) on 2 November 1964. Robert H. Dicke, Robert H. Dicke Papers, 1939–1996, Princeton University Library, Department of Rare Books and Special Collections, Manuscripts Division (Princeton, New Jersey), Box 3, Folder 3.
Although Dicke himself was absorbed in an attempt to measure the visual oblateness of the sun from 1964–1966. Dicke Papers, Box 4, Folders 4 and 5.
Letter from Wilkinson to Alessandro Melchiorri. David T. Wilkinson, David Wilkinson Papers, 1957–2002, Princeton University Library, Department of Rare Books and Special Collections, Manuscripts Division (Princeton, New Jersey), Box 4, Folder 9: Correspondence 1992–1993.
P.J.E. Peebles, Physical Cosmology (Princeton: Princeton University Press, 1971).
John Mather, one-day Oral History Interview with the author, Goddard Space Flight Center, Greenbelt, Maryland, 2 May 2018.
Richard A. Muller, “The Cosmic Background Radiation and the New Aether Drift,” Scientific American 238 (1978): 64–74. Peebles’ 1971 book included a section titled “The Aether Drift Experiment.”
Mather and Boslough, The Very First Light, 176.
James E. Peebles, Lyman A. Page, Jr., and R. Bruce Partridge, Finding the Big Bang (Cambridge: Cambridge University Press, 2009), 209.
Mather, Oral History Interview.
The Shaw Prize, Autobiography of Charles L. Bennett, 2010,
Peebles, Page, and Partridge, Finding the Big Bang, 210–211.
Mather and Boslough, The Very First Light, 231–245.
Bennett, Oral History Interview.
George Smoot and Keay Davidson, Wrinkles in Time: Witness to the Birth of the Universe (New York: William Morrow & Co., Inc., 1993).
The Shaw Prize, Autobiography of Charles L. Bennett.
I thank Dr. Edward Wollack for providing outreach material prepared by the Team. See all four postcards (NP-2002-6-467-GSFC, NASA-WMAP Science Team, 2002) here:
L2 also became home for the Planck spacecraft and the future James Webb Space Telescope.
“Greetings from L2.” Postcard 1 of 4.
“Microwaves in Space.” Postcard 2 of 4.
“Fingerprint of the Universe.” Postcard 3 of 4.
“Shape of the Universe.” Postcard 4 of 4.
McCray, “How Astronomers Digitized the Sky,” 931–933. See
D’Onofrio and Burigana, Questions of Modern Cosmology, 73.
Max Tegmark, Our Mathematical Universe: My Quest for the Ultimate Nature of Reality (New York: Vintage Books, 2014), 58–59.
Bennett, Oral History Interview.
Bennett, Oral History Interview.
Bennett, Oral History Interview.
“MAP Poster” (MAP Science Team, NASA Goddard Space Flight Center, 1998),
Birgit Schneider, “Climate Model Simulation Visualization from a Visual Studies Perspective,” WIRE s Climate Change 3 (2012): 188.
Lorraine J. Daston and Peter Galison, Objectivity (New York: Zone Books, 2007), 405.
Bennett, Oral History Interview.
“Constant Controversy,” Sky and Telescope 137, no. 6 (June 2019): 22–29. NASA’s future Roman Space Telescope will address these discrepancies,
For a more traditional interpretation of aesthetics in relation to astronomy, see Michael Lynch and Samuel Edgerton, “Abstract Painting and Astronomical Image Processing,” in The Elusive Synthesis: Aesthetics and Science, ed. Alfred Tauber (Dordrecht: Kluwer Academic Publishers, 1996), 103–124.
Barry Mazur, “The Nature of Explanation,” University of Utah Symposium on “Mathematics, Language, and Imagination” (November 2009),