Making sense of that black hole

Black holes are not even holes, but the exact opposite: places of unimaginable super-packed density. (Event Horizon Telescope Collaboration)

It’s really not the way it seems. The news captions were misleading. In truth, that wasn’t a photo of a black hole. Nor was it the first ironclad proof that they exist. And it didn’t finally prove that Einstein was right. 

But the world loved it and the media went crazy. And behind it lay amazing science and head-spinning technology.


Where to begin? The New York Times ran a long article written by former Woodstocker Dennis Overbye, whose prose was poetic but whose descriptions of the image were skeletal. So, let’s begin with what we were seeing. It was not a photograph of a black hole, taken by some super-telescope. It was an artificially created image assembled from reams of mathematical data attained by the process of interferometry. That’s when several radio telescopes – eight, in this case – stare at a single place at the same time so that their data can be carefully spliced together to yield information that no single telescope could obtain. That info is then assembled to construct a false-color image.

Long-baseline interferometry is what produced the first solid information about the size of the star Betelgeuse three decades ago. Though the largest-appearing star in the sky, it’s 640-light-year distance means that it’s just a point of light in even the largest telescope. But interferometry data revealed its true apparent size, which led to that team releasing an “image” (a visual simulation) of a small orange sphere.

This black hole lies 100,000 times farther away, in the heart of the famous giant elliptical galaxy M87. It lurks 55 million light-years behind the stars of Virgo. The interferometry data were able to show a sort of shadow in the radio waves emanating from objects behind the black hole. This round shadow, ten times larger than the black hole (meaning its event horizon), is what is depicted in this image. So the blackness is not the edge, surface or tunnel entrance of some black object.

Incidentally, over the past 35 years, visitors to our Overlook Observatory have been shown the same black hole – or, to be more specific, the amazing violent blue jet of material hurled away from the west side of this black hole, at the heart of M87. It’s an amazing sight in large backyard or observatory telescopes.

As for the claim that it was the first proof of black holes, that’s just plain silly. More than 30 years ago, on this very page, we talked about Cygnus X-1: the black hole that sits near the star Deneb in the summer sky. For all the reasons we outlined then, the fact that Cygnus X-1 is a black hole was absolutely clinched. Since the ’70s, no astronomer has regarded them as merely theoretical.

But false claims and confusion are nobody’s fault, since basic facts about black holes remain puzzling even to astrophysicists. They’re not even holes, but the exact opposite: places of unimaginable super-packed density. And although the image showed a black blob of a particular size, an actual black hole has no size. Physicists are unsure whether they have all collapsed into specks that occupy zero volume and thus vanish from our universe altogether (a process that would take infinitely long to any outside observer such as ourselves), or whether some unknown process stops the collapse at some point.

The public imagines them gobbling up stars and planets. But their gravity is actually no different from other similar-mass objects at the same distance. If our Sun collapsed to become a black hole, we’d continue orbiting just as before. We wouldn’t get pulled in. We wouldn’t even be tugged with the slightest increased “pull.”

As to what it’s like in a black hole…our entire universe is almost certainly a black hole, meaning that no amount of speed could let you escape from it. So if you’ve wondered what the inside of a black hole looks like, just take a peek into your underwear drawer.

Want to know more? To read Bob’s previous columns, visit our Almanac Weekly website at Check out Bob’s podcast, Astounding Universe, co-hosted by Pulse of the Planet’s Jim Metzner.