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Comment: What does it actually mean to see a black hole?



"We saw what we thought was invisible," the astronomer said, as if someone knew that the ear of history was being pushed to the door. He stood in the silent attention of the room in Washington, when he called the picture on the screen behind him. You know it now: a smoke ring, an orange donut, a blurred circle of light around a deep darkness. At the end of the day, it would be known to millions of people as the first photo of a black hole.

The Event Horizon Telescope (EHT), a collaboration of eight radio telescopes around the world, made this picture together from observations from the Antarctic and Arizona. Since no single telescope is strong enough to distinguish as small a detail as a black hole 55 million light-years away, the scientists used these eight observatories to simulate a much larger instrument, one as large as the earth itself. It took two Years, and more than 200 people searched and refined the data collected in April 201

7 over four days to focus on the final famous image.

As I repeat the story on Wednesday in the news, the profound simplicity of the picture that was obtained through such complex means struck me. Confused by algorithms and vectors, the photo is not the rendering of an artist or a model – our earlier attempt to depict a black hole – but it's still a construction. The radio waves collected by the telescopes and assembled into a picture are translated into color to our advantage. They can not pick up a telescope, even the size of the earth, and convince themselves of it. And yet, during the course of the day, I heard a line again and again: we see a black hole. They "do not" "recognize" by their radio signature, do not dig up any further evidence of their existence – they actually see it.

Far above its scientific value – the experiment is perhaps most notable in addition to its pure technological achievement, because it does not disturb the established rules of the theory of relativity – the picture seems to be important to us, because it is an image. Our certainty in unquestionable orange and black has a new weight.

We have not lacked proof of the existence of black holes. Since Albert Einstein reluctantly predicted them in 1916 with his Theory of Relativity, we have gathered evidence. In 1935, physicist Subrahmanyan Chandrasekhar suggested that a star could become so massive that it would collapse under its own gravity. Then, in 1969, Donald Lynden-Bell suggested that supermassive black holes in the center of galaxies could account for the enormous energy signatures discovered there, far beyond what stars alone could produce. 2015 came with the cosmic "Zing" almost definitive proof! That was the sound of two black holes a billion light-years away. For most scientists, gravity-wave detection was the cause: black holes were out there that upset space-time even if we had never seen them.

But images of the universe have an eerie power over us: these are so miraculous aspects they never fit our understanding. Naked, our eyes perceive the night sky as a cosmic vortex of dust and diamonds, an indication of greater complexity. In the early 1600s, Galileo and others directed the first telescopes into the sky to describe the mountainous face of the moon. The dark speckled sun was spinning slowly around its axis, and the three shining Jupiter moons were wiggling in their distant orbits. Seeing gave us irrefutable proof of the vastness of the universe, its chaotic, ballistic physics. When we saw this for the first time, we believed in it.

I grew up with these cosmic visions. I remember sleeping under placards from the Pillars of Creation and the Cats Eye Galaxy at the Space Telescope Science Institute in Baltimore, while my mother read data and made suggestions for proofreading at her desk. When I was a little older, I talked to a toy propeller in the hallway and watched him move over the currents above my head. My mother told me that looking into space with a telescope would be like looking back in time. Nothing has disappeared from the universe, she said, it's just farther away. I understood that everything could be known if we could only see far enough.

Our telescopes are bigger and more powerful than ever before. They are mirrors that tilt from mountain peaks and deserts to the sky or like huge insects orbiting on their stiff solar cell wings. They swallow light, not just the visible spectrum of blues and reds, but also the x-rays and radio waves we're blind to, revealing the intricate structures of distant galaxies and misty technicolor nebulae. These are landscapes we could never see for ourselves, but when they see their pictures, they become real to us.

Black holes had escaped. They are the definition of the invisible: mass and volume that turn outward, cosmic sinkholes from whose irresistible gravity nothing can escape – not a single lousy photon.

But light has always helped us to understand what we could not see: T.S. Eliot wrote of the "visible remembrance of invisible light" by tracing the seen and the invisible. Early astronomers followed the invisible presence of gravity through the stellar arcs around their axes. Modern people use the oscillating brightness of stars to guess the planets they can orbit, and those distant suns are torn out of balance. And Hubble's observations of an expanding universe criss-crossed with distorted light have revealed the presence of dark matter, an idea so strange and slippery that it's hard to come by.

My mother examined black holes at the Space Telescope Science Institute Those who began to understand scientists were also at the center of most galaxies, spinning around their stars like dervishes. We could not see them, but we could see the shining clouds of light and energy surrounding them. The paradox of the black hole is that although no light can escape its limits, the regions beyond the event horizon are some of the most energetic and brightest places in the universe. From her, I saw how one could follow the traces of the visible to hunt for signs of the invisible.

Behind the halo in the center of Messier 87, one of the two galaxies in the crosshairs of the EHT recalls the challenges we face in the search for these invisible objects. The second goal of the EHT, Sagittarius A *, is the black hole at the center of our own galaxy. Although much closer to us than M87, it's also smaller and more susceptible to a shift in focus, like a fidgety student on an image day.

But unseen it makes itself known. In the Milky Way's brightly lit hub, stars hurl their way around a massive and invisible object, accelerating past the rotating engine with each brush, then slowing down at the zenith before returning. We can see her clearly. We can see through her dance what she is failing to do. We can not see it yet. But we know that it is there.

Amelia Urry is a scientific writer and poet in Seattle. She is also the daughter of two astrophysicists.

  Amelia Urry
Amelia Urry


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