Extract from the book "Light in the Darkness. Black holes, the universe and us” by Heino Falcke, Professor of Astroparticle Physics and Radio Astronomy at Radboud University. Falcke stood at the initiative of the first image of a black hole, which was published in April 2019. The text below is preceded by a look back at another achievement of Falcke's team: the launch of a radio antenna to the far side of the moon.
Celestial calm. The first thing you notice when you arrive in outer space is the utter stillness. The engines have shut down; outside all sound dies away. The Hubble Space Telescope floats 550 kilometers above the surface of the Earth—almost 70 times the height of Mount Everest. The telescope glides through an atmosphere that is about 5 million times thinner than the atmosphere on the Earth’s surface. Sound waves, actual vibrations in the air, are no longer audible to human ears: not a rustle, not a word; not even the most violent explosion on Earth could be heard up here.
As an astronomer, I use the space telescopes that orbit the Earth, listen to the stories told by the astronauts that have been up there, and look at the images they’ve brought back. In my head I’m floating quietly in space, seemingly weightless, but actually I’m speeding around the Earth at a breakneck 27,000 kilometers per hour. My strong centrifugal force could potentially fling me out of orbit, but the powerful pull of the Earth’s gravity evens this force out and keeps me on course. This is the secret behind all orbital motion around a celestial object. Weightlessness doesn’t mean you’re free from gravity’s pull. In orbit, gravity still has us in its grip, but we feel weightless because the centrifugal force and the force of gravity are perfectly balanced. Actually we’re in free fall, but we keep missing the Earth again and again because we’re circling it on a wide trajectory, so neat it could have been drawn with a giant compass. If we were to slow down, our trajectory would get ever smaller and steeper, until eventually our free fall would end abruptly in an impact crater on Earth. But of course no one wants that!
The scant atmospheric friction with which our spaceship has to contend is so minimal that we can orbit the Earth for years nearly unimpeded, without firing our rockets even once.
So long as we’re orbiting in space, we can enjoy the one-of-a-kind view of Earth from up here. Godlike, we look upon this blue pearl, set against the black velvet backdrop of the universe. Continents, clouds, and oceans unleash a rich, wild play of colors. At night, flashes of lightning, glowing cities, and the shimmering auroras light up the global stage—a spectacular sight. Borders disappear; with our allencompassing view we see the Earth as the shared home of all humankind. The line that divides us from the cold of space is clear and sharp. Only now, from up here, do we understand how thin the layer of air is that protects us from hostile space and makes life possible. The weather and climate play out in just a small strip above the Earth. How fragile, how vulnerable this proud planet seems all of a sudden! We owe such fascinating sights—and insights—in space to modern technology. But through its reckless use on Earth we’re also destroying the very basis for our lives on this unique blue planet.
Every time I see these beautiful images of Earth, I also sense the loneliness and emptiness, the pain and suffering that are felt all over the world. “He spreads out the northern skies over empty space; he suspends the earth over nothing,” so cried sorrow-stricken Job millennia ago. The nothingness of heaven, spread out like a black canvas, and in the middle—our planet Earth! The biblical writer was not granted this view from above, and yet in his visions he already perceived the Earth as a whole. Humanity’s old visions are today filled with new images, provided to us by modern technology. A swarm of satellites with cameras and sensors trained permanently on our planet captures clouds, continents, and oceans in breathtaking detail. Job, who sees the Earth hanging upon nothing, submits his grievance to God. What Job experiences is something profoundly human: pointless suffering. Still today this planet is a complex mix of suffering and beauty. An individual human cannot be seen from space. Suffering can only be grasped from up close; from afar, everything on Earth looks sublime and extraordinary. Even hurricanes, floods, and forest fires take on a morbid fascination from up above. In space one is far removed from the suffering of individuals, which plays out by the billions down below. From space our earthly problems are incomprehensible. Doesn’t this “omniscient view” often look past humans themselves?
It is more than astounding how this sober and technical research can cause such a lasting change even in hardened space travelers. After the cosmonaut Yuri Gagarin became the first in 1961, more than 550 people have been in space. Almost all have reported that their amazement at the sublime fragility of the Earth left a deep impression on them, left them profoundly changed as individuals. The experience of gazing upon the entire globe seems akin to an ecstatic state. The author Frank White called this phenomenon, which he studied and described in psychological detail, the “overview effect.” What does the sight of the planet trigger within us? How does it change us? How can we make use of this effect? Doctors have been researching the “overview effect” ever since it was first described. The Earth is unique; there is nothing in space comparable to it, so far as we know. Astronauts have the same impression. Floating above the Earth like an angel and seeing everything from above doesn’t leave us humans cold. Let us therefore be inspired by these new images from and of space, without overlooking the human individual.
Heino Falcke, "Light in the Darkness. Black holes, the universe and us”
On June 1st Netflix will release a documentary on the making of the first image of a black hole: Black holes. The edge of all we know. A documentary film following the quest to understand the most mysterious objects in the universe.