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Around the horizon of a black hole, an edge of the universe, light is captured, spun into orbit by the black hole’s powerful gravitational pull. Lying within the orange donut in the famous first image of a black hole, this “photon ring” would be a prize to measure—it would reveal the nature of spacetime itself, directly, near the horizon. Indeed, the shape of this pure ring of light tells everything about the black hole. With the stakes this high, a new collaboration—physicists, astronomers, engineers from around the world—has formed to loft a spacecraft that capture the photon ring. We are at the beginning of what is probably a ten-year effort—this is a film about the start of that adventure.

A film by Peter Galison, Michael Johnson, and Chyld King

My world was jolted by two shadow images: one, thrilling, the other terrifying.  After a years-long effort—with 200 other scientists—we made the first image of a black hole, its shadow of no return.  Then I fell into debilitating pain. A deadly shadow blot appeared on an MRI of my spine.  Faced with emergency surgery and no assurance of success, I sought comfort in memory images from the past and, from collaborative work that engrossed me: images of the whole visible universe could be stored in light circling a black hole.  It was a universal memory. An experimental back and forth between the innermost-personal and the astronomical, where shadows and consolation cross.

This white paper outlines the plans of the History Philosophy Culture Working Group of the Next Generation Event Horizon Telescope Collaboration.

Recent developments in very long baseline interferometry (VLBI) have made it possible for the Event Horizon Telescope (EHT) to resolve the innermost accretion flows of the largest supermassive black holes on the sky. The sparse nature of the EHT’s (u, v)-coverage presents a challenge when attempting to resolve highly time-variable sources. We demonstrate that the changing (u, v)-coverage of the EHT can contain regions of time over the course of a single observation that facilitate dynamical imaging. These optimal time regions typically have projected baseline distributions that are approximately angularly isotropic and radially homogeneous. We derive a metric of coverage quality based on baseline isotropy and density that is capable of ranking array configurations by their ability to produce accurate dynamical reconstructions. We compare this metric to existing metrics in the literature and investigate their utility by performing dynamical reconstructions on synthetic data from simulated EHT observations of sources with simple orbital variability. We then use these results to make recommendations for imaging the 2017 EHT Sgr A* data set.

General relativity predicts that images of optically thin accretion flows around black holes should generically have a “photon ring”, composed of a series of increasingly sharp subrings that correspond to increasingly strongly lensed emission near the black hole. Because the effects of lensing are determined by the spacetime curvature, the photon ring provides a pathway to precise measurements of the black hole properties and tests of the Kerr metric. We explore the prospects for detecting and measuring the photon ring using very long baseline interferometry (VLBI) with the Event Horizon Telescope (EHT) and the next-generation EHT (ngEHT). We present a series of tests using idealized self-fits to simple geometrical models and show that the EHT observations in 2017 and 2022 lack the angular resolution and sensitivity to detect the photon ring, while the improved coverage and angular resolution of ngEHT at 230 GHz and 345 GHz is sufficient for these models. We then analyze detection prospects using more realistic images from general relativistic magnetohydrodynamic simulations by applying “hybrid imaging”, which simultaneously models two components: a flexible raster image (to capture the direct emission) and a ring component. Using the Bayesian VLBI modeling package Comrade.jl, we show that the results of hybrid imaging must be interpreted with extreme caution for both photon ring detection and measurement—hybrid imaging readily produces false positives for a photon ring, and its ring measurements do not directly correspond to the properties of the photon ring.

We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of λ = 1.3 mm. The EHT data resolve a compact emission region with intrahour variability. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of 51.8 ± 2.3 μas (68% credible interval). The ring has modest azimuthal brightness asymmetry and a comparatively dim interior. Using a large suite of numerical simulations, we demonstrate that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ∼4 × 10⁶ M_⊙, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. Our model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50°), as well as nonspinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way, and for the first time we connect the predictions from dynamical measurements of stellar orbits on scales of 10³–10⁵ gravitational radii to event-horizon-scale images and variability. Furthermore, a comparison with the EHT results for the supermassive black hole M87* shows consistency with the predictions of general relativity spanning over three orders of magnitude in central mass.

1930, Madras, India. On a steamship to England, 19-year-old Indian physics prodigy, Subrahmanyan Chandrasekhar makes a paradigm-shattering discovery about the life cycle of stars: a discipline pioneered by Sir Arthur Eddington, the world’s most famous astronomer and Chandra’s new advisor. After years of work under his mentor's watchful eye, Chandra presents at a public forum, only for Eddington to denounce his protégé and his work. A half-century later, after a more conservative career, Chandra is awarded the Nobel Prize for the work begun on board that ship to England. Grounded in his recorded memories, “Shattering Stars” alternates between realistic and imaginary animation.

Black holes stand at the limit of what we can know. The Event Horizon Telescope links observatories across the world to simulate an earth-sized telescope. With this tool the team pursues the first-ever picture of a black hole, resulting in an image seen by billions of people in April 2019. Meanwhile, Hawking and his team attack the black hole paradox at the heart of theoretical physics—Do predictive laws still function, even in these massive distortions of space and time? Weaving them together is a third strand, philosophical and exploratory using expressive animation. “Edge” is about practicing science at the highest level, a film where observation, theory, and philosophy combine to grasp these most mysterious objects.

Objectivity has a history, and it is full of surprises. In Objectivity, Lorraine Daston and Peter Galison chart the emergence of objectivity in the mid-nineteenth-century sciences — and show how the concept differs from alternatives, truth-to-nature and trained judgment. This is a story of lofty epistemic ideals fused with workaday practices in the making of scientific images.

From the eighteenth through the early twenty-first centuries, the images that reveal the deepest commitments of the empirical sciences — from anatomy to crystallography — are those featured in scientific atlases: the compendia that teach practitioners of a discipline what is worth looking at and how to look at it. Atlas images define the working objects of the sciences of the eye: snowflakes, galaxies, skeletons, even elementary particles. Galison and Daston use atlas images to uncover a hidden history of scientific objectivity and its rivals. Whether an atlas maker idealizes an image to capture the essentials in the name of truth-to-nature or refuses to erase even the most incidental detail in the name of objectivity or highlights patterns in the name of trained judgment is a decision enforced by an ethos as well as by an epistemology.

As Daston and Galison argue, atlases shape the subjects as well as the objects of science. To pursue objectivity — or truth-to-nature or trained judgment — is simultaneously to cultivate a distinctive scientific self wherein knowing and knower converge. Moreover, the very point at which they visibly converge is in the very act of seeing not as a separate individual but as a member of a particular scientific community. Embedded in the atlas image, therefore, are the traces of consequential choices about knowledge, persona, and collective sight. Objectivity is a book addressed to any one interested in the elusive and crucial notion of objectivity — and in what it means to peer into the world scientifically.

Available at: Amazon

A dramatic new account of the parallel quests to harness time that culminated in the revolutionary science of relativity, Einstein's Clocks, Poincaré's Maps is "part history, part science, part adventure, part biography, part meditation on the meaning of modernity....In Galison's telling of science, the meters and wires and epoxy and solder come alive as characters, along with physicists, engineers, technicians and others....Galison has unearthed fascinating material" (New York Times).

Clocks and trains, telegraphs and colonial conquest: the challenges of the late nineteenth century were an indispensable real-world background to the enormous theoretical breakthrough of relativity. And two giants at the foundations of modern science were converging, step-by-step, on the answer: Albert Einstein, an young, obscure German physicist experimenting with measuring time using telegraph networks and with the coordination of clocks at train stations; and the renowned mathematician Henri Poincaré, president of the French Bureau of Longitude, mapping time coordinates across continents. Each found that to understand the newly global world, he had to determine whether there existed a pure time in which simultaneity was absolute or whether time was relative.

Esteemed historian of science Peter Galison has culled new information from rarely seen photographs, forgotten patents, and unexplored archives to tell the fascinating story of two scientists whose concrete, professional preoccupations engaged them in a silent race toward a theory that would conquer the empire of time. 

Available at: Amazon

Between the disciplines of art history and the history of science lies a growing field of inquiry into what science and art share as both image-making and knowledge-producing activities. The contributors of Picturing Science, Producing Art occupy this intermediate zone to analyze both scientific and aesthetic representations, utilizing disciplinary perspectives that range from art history to sociology, history and philosophy of science to gender studies, cultural history to the philosophy of mind. Organized in five sites--Styles, The Body, Seeing Wonders, Objectivity/Subjectivity, and Cultures of Vision--their topics extend from Cinquecento theories of female reproduction to the technologies of cloning, from medieval depictions of the stigmata to electrical metaphors for sex, from astronomical drawings to radioencephalography, from Phoenician griffons carved in ivory to factories cast in concrete. The internationally renowned contributors go beyond both science wars and culture wars by exploring substantive links between systems of visual representation and knowledge in science and art.

Image and Logic is the most detailed engagement to date with the impact of modern technology on what it means to "do" physics and to be a physicist. At the beginning of this century, physics was usually done by a lone researcher who put together experimental apparatus on a benchtop. Now experiments frequently are larger than a city block, and experimental physicists live very different lives: programming computers, working with industry, coordinating vast teams of scientists and engineers, and playing politics.

Peter L. Galison probes the material culture of experimental microphysics to reveal how the ever-increasing scale and complexity of apparatus have distanced physicists from the very science that drew them into experimenting, and have fragmented microphysics into different technical traditions much as apparatus have fragmented atoms to get at the fundamental building blocks of matter. At the same time, the necessity for teamwork in operating multimillion-dollar machines has created dynamic "trading zones," where instrument makers, theorists, and experimentalists meet, share knowledge, and coordinate the extraordinarily diverse pieces of the culture of modern microphysics: work, machines, evidence, and argument.

Available at: Amazon