Every milestone since Einstein published his theory of general relativity has been leading up to this
On Wednesday, the world got to see what a black hole looks like in the flesh. The image-reveal of the black hole at the centre of the galaxy, Messier 87, will go down as a seminal moment in the annals of the history of man’s understanding of the universe. It corroborates Albert Einstein’s theory of general relativity, which helped predict black holes some eight decades before, and thereby should inform scientific discourse in unprecedented ways. It is also living proof, much like the Large Hadron Collider, of the gains of pooling minds and resources from across the globe—200 scientists, part of the Event Horizon Telescope (EHT) collaboration, produced the image, working on signals from eight radio observatories located in remote, high-altitude sites in Hawaii, Spain’s Sierra Nevada mountains, the Chilean desert and the Antarctic ice-sheet. These radio telescopes are sensitive to wavelengths of about a millimetre—at that level of radio frequency, the radiation from a black hole can penetrate interstellar dust and gases. While the existence of black holes was theoretically proven, actually seeing one (or more correctly, its shadow) was a gargantuan challenge, since they have gravitational fields so strong that even light can’t escape its pull, and thus all that can be visualised is a singularity—a concentrated point of infinite density where the laws of space-time can’t exist—enveloped by a shell of darkness called the event horizon, the absolute outer bound from where nothing can escape the singularity’s pull. Beyond this is the photon orbit, a region from where light could theoretically escape but is unlikely to.
The M87 black hole is 55 million light years away from Earth, and packs a mass roughly equivalent to over 6.5 billion Suns, but its event horizon doesn’t extend beyond 40 billion km, which Science helpfully notes, is about four times the diametre of Neptune’s orbit—not impressive in the intergalactic context. The EHT team harnessed most of the mm-wavelength telescopes worldwide and refashioned it into a virtual, Earth-sized telescope through what is known as very-long-baseline interferometry. Having obtained all the data that they needed to generate the image by April 2017, the scientists at EHT got down to processing that—imagine the volume of data that needed to be processed if the image could be generated only by 2019. It was so large—4 petabytes in all—that it could not be transmitted to large computers at MIT, the US, and Max Planck Institute for Radio Astronomy, Germany. This is where Katie Bouman, who is the now the toast of the scientific community worldwide and her team come in—they wrote the programming that eventually converted the mammoth data into the image. Bouman has become the poster-girl for women in STEM overnight. Given how structural the gender bias in STEM is—evident from the fact that women whose work has been later recognised as seminal to path-breaking scientific developments have seldom received their due even within the scientific community—an idol who shot to stellar fame is manna from heaven for righting STEM’s gender gap.
Every milestone since Einstein published his theory of general relativity has been leading up to this. Basing on Einstein’s works, German scientist Karl Schwarzschild proposed that an infinitely dense object would exert gravitational pull so strong within a certain distance from itself that not even light can escape it. In 1939, this went from being a mathematical observation to the prediction of massive stars collapsing to form such an object, by American scientist Robert Oppenheimer and his team. In 1967, Jocelyn Bell Burnell discovered pulsars—super dense, spinning dying stars—confirming that Oppenheimer’s prediction may be true; Burnell never received the Nobel, though the discovery was recognised by the Nobel committee in 1974. There has been much indirect evidence since then, the most compelling of which came in 2015 when LIGO detected ripples in space-time emitted by the cataclysmic merger of two black holes.