This is issue #720, which mathematically is equal to 6 factorial, written “6!”. That’s 6 x 5 x 4 x 3 x 2 x 1. I remember in high school (I think it was), being the dorky kid I was at the time (not like now haha ha ha) writing out the first few terms of the factorial series and marveling at how quickly it got huge (unlike the Fibonacci series, which I also wrote out and added to when I got bored in class, which was a lot). Anyway, this won’t happen again until issue 7!, or #5040, so it may be a while (roughly 27 years at this rate because yes I like doing the math).

Actually, this is three things about my book.

The first is that the paperback version is now available! You can get it at your favorite bookseller, and I have a list of them at my UAS site (click the “Buy Now” icon at the upper right).

I’m pretty excited about this; the paperback is of course less expensive than the hardcover. It also marks the final part of the whole book-writing process; the hardcover, e-version, and audio version (which I narrated) came out first, then the softcover a year later. So with this, the book is officially done.

…unless sales are so huge it gets another printing, or it gets optioned for a TV series (feel free to tell any science production company people you know about it). I’m still hoping!

Second, the terrific Ambre Trujillo of The Planetary Society made a nice Instagram video saying how much she liked the book (it’s on YouTube too if you don’t like IG). Thanks, Ambre!

Third, I am extremely happy to let y’all know that I was interviewed for the Smithsonian Institution’s National Air and Space Museum (!!) magazine Air and Space Quarterly about Under Alien Skies!

I think it’s a really fun interview. I was being unusually lucid, and I’m especially proud of my answer for the last question. You can read it here, and it’s in the Spring 2024 print issue, too.

What would it look like to fall into a black hole?

In my own case it wouldn’t matter, because — as much as I love the physics and astronomy of the situation and find it fascinating — I’d be too busy screaming, panicking, running around in circles flapping my arms wildly around, etc.

But in general, what would you see? The physics is actually pretty complicated, because the gravity of a black hole is so severe that the view is massively distorted. Matter warps space via gravity, and light has to follow that bent path like a car following a curving road. What you see gets twisted up like looking into a funhouse mirror (maybe it’s time to retire that analogy; who the heck has been to a funhouse and seen the wobbly mirror?).

Even worse, as you get closer to the black hole the gravity gets stronger, so trying to map out the way things look using physical models is complicated. And the cherry on top is that this all has to be done using general relativity, which is, well, hard.

But not impossible! An astronomer at NASA’s Goddard Space Flight Center did the math (and the coding) to show what it would look like as you fell in. He actually did two scenarios; one where you fall in toward the black hole but not far enough to cross the event horizon — in other words, you stay just on this side of The Point Of No Return — so you get flung back out, and another where you fall all the way in.

With the help of a NAA supercomputer he turned his math into visualizations, and they’re exactly as trippy as you’d hope. 

First up: Falling all the way in. I suggest going to the YouTube page and making it full screen, because wow. 

In the video the black hole is surrounded by an accretion disk, a flat ring of material superheated by friction and glowingly hot. It looks like a sombrero due to the gravitational distortion of the black hole; I have a detailed description of all that on The Old Blog. The narrow bands of light closer in to the black hole are the photon rings, the distances out where a photon might circle the black hole one or more times before escaping. Also, the Milky Way is shown in the background, and the view of that gets warped all goofily too as the light falls toward the black hole (the two glowing patches are satellite galaxies of the Milky Way).

The first minute of the video is simply what you see with no explanation. The next 1.5 minutes or so are annotated so you can get a better understanding of events. A more detailed view showing the photon rings comes next.

The second video shows what it’s like to fly past the black hole on an escape trajectory, so you don’t have to deal with all the messy bits about being spaghettified and dying. 

The NASA press release page has more info.

One part I like is how one side of the black hole’s accretion disk is brighter than the other. That’s due to relativistic beaming, a very strange outcome of relativity. If an object is approaching you at very near the speed of light, the light it emits gets focused into the direction of its travel, so it appears brighter (in other words, light that might be emitted to its side when it’s stationary actually gets bent toward you as if its heading toward you; you see more light so it looks brighter). As material in the disk screams around the black hole, some it is approaching you and some receding; the former looks brighter. I love it when little details like that are easily seen.

It’s fascinating and mesmerizing, isn’t it? Black holes are just so damned strange! It’s amazing to me that we can understand them at all, let alone be able to create visualizations like these so others can experience it too. Safely, I might add. <shudder>

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