The force of gravity is proportional to mass and diminishes with distance. When a star dies, there’s a lot of mass in a pretty small space, and no more force pushing outward against the gravity. So the star crushes down, becoming even smaller and denser, further concentrating the gravitational force pulling toward the center. With enough mass it condenses into a tiny nubbin, with gravitation so great that nothing, not even light, can escape. That’s a black hole.
With a ratio of mass to volume virtually infinite, the normal laws of physics cease to apply, which is called a “singularity.” Many formerly doubted this could occur in reality. Now we know it does. There may be a black hole at the center of every galaxy. Meantime, black holes’ weirdness captured popular imagination. Gravity so strong it sucks in anything getting near, while nothing gets out. “Black hole” became a useful metaphor (especially in 2017-21).
When we discovered the Universe is expanding, running that film backwards gets you to something that also has vast mass concentrated into virtually zero space — again a singularity where the laws of physics break down. This has led to speculation that the “Big Bang” and black holes are connected — that a black hole could detonate big bangs — perhaps answering the conundrum of seemingly getting something from nothing. With new universes being birthed all the time out of black holes.
You may have seen in 2019 our first photo of a black hole. We watched a great Netflix film about the scientists working on what was a massive photography project. A big problem was that a black hole is, well, literally black, no light escaping. But it does produce “Hawking radiation” in the surrounding space.
Still, getting a photo was a huge challenge because so few photons reach us across the cosmic vastness. The film illustrated this vividly by first showing a grid of squares, with one small square containing our solar system. Then it zoomed out to show that whole grid as just one square in a far bigger grid. Then it did it again. And again and again and again. I lost count, before we finally saw a grid big enough to contain both our solar system and the black hole.
That was one of two the team targeted. The other was a thousand times bigger — and a thousand times farther away.
The paucity of photons reaching us meant an ordinary telescopic photo would be, like, one or two pixels. Hardly helpful. To get a decent meaningful image would have required a camera the size of the Earth. So that’s what they built — by coordinating a whole slew of telescopes all across the planet. Each making images simultaneously. Having good visibility conditions at all of them, simultaneously, was a problem too. Somehow they succeeded. The result was an immense amount of data shipped on hardware from all those locations to a central clearinghouse where computers could put together the pieces of this stupendous jigsaw puzzle. Revealing the picture of a black hole.
Meanwhile . . . the film also focused on a group of theoreticians working with the late Stephen Hawking, he of “Hawking radiation,” the leading thinker on black holes who practically invented them. The main concern was with what they called the “information paradox.” “Information” here means more than its common parlance; it refers to what’s encoded in the structure of any physical object. In that sense, your body, for example, entails many trillions (or quintillions?) of bits of information. Throw it into a black hole and that information seemingly disappears. That bothered the theoreticians, a lot, contravening their intuition for how the Universe should operate. (This is about as well as I could manage to understand the matter.)
So they banged their heads against the mathematics. I didn’t begin to grasp the interplay between the very complex mathematics and the physical phenomena. But finally, it seemed, they did get the sums to work out such that information sucked into a black hole is not truly annihilated but is conserved in some manner.
But here is what struck me viewing this film. All the numerous people involved in these enterprises, especially the photography effort, exemplify what I see as our great human project. To understand — everything. And to use that understanding to imbue our lives with meaning and fulfillment. With nothing given to us but what we seek and find ourselves. Everything else pales beside the immensity of that great human project. Membership in this species fills me with pride.
