When Tharp showed her results to geologist Bruce Heezen, he dismissed them because they implied continental drift. He initially described her work as "girl talk."

Heezen, of course, eventually came around. They collaborated for decades, and he championed her work.

He wrote "What people think the bottom of the ocean looks like, that is, what most scientists and informed laymen think it looks like, is what Marie Tharp thinks it looks like."

At the time of Tharp's discovery, the idea of continental drift was not accepted by most scientists.

As Tharp put it, "Almost everyone in the United States thought continental drift was impossible."

But as she assembled her plots, the evidence was right there: A rift valley running along the ridge where new material emerged from within the Earth as the plates on either side moved apart.

Geologist Marie Tharp was born #OTD in 1920.

She built the first accurate map of the Atlantic Ocean floor, discovering the Mid-Atlantic Ridge that provided evidence for seafloor spreading and plate tectonics.

Image: Lamont-Doherty Earth Observatory

@Dorolfe @bstacey The Sacred Text

@JasonPerseus it’s a good ‘un

Good evening.

Mother and baby loon.

Good evening, from somewhere in Michigan.

@cra1g @darrelplant Not weird at all! I think that preference I s the basis for the whole OSR movement.

@darrelplant Nice!

A good premise for a low-level adventure would be set in a college for magic where students use Magic Mouth as a version of social media. The wall where they post is cursed with a sort of magical contagion that causes them to become obsessed. First they neglect their studies, then taking care of themselves, then even eating. The party has to break the curse, and figure out who is behind it. No one in the party can be a magic-using character.

Gygax created a cherished part of my childhood. Pouring a cup of coffee and digging in to some 1st edition books, modules, and maps this evening.

Anyway, most people don't know this, but back in 1978 Gary Gygax also invented posting on social media.

Image: Dave Trampier

Gygax claimed to be a biological determinist. Based on his limited experience, he decided women just didn’t enjoy D&D. (Though, he added, they were just as good at it as men.)

If you also find this ridiculous, I encourage you to cast “Speak with Dead” and let him know.

Game designer Gary Gygax, who co-created Dungeons & Dragons with Dave Arneson, was born #OTD in 1938.

He had some lame views about women being able to enjoy RPGs (and who knows what else). But he’s not the boss of enjoying D&D, so I hope you enjoy it with especial relish today.

@slothdude friend-limited process

The best case scenario starts with an "extremal" black hole — one that is spinning as rapidly as possible. In that case one could, in principle, convert something like 29% of the black hole's original mass into energy.

That’s an awful lot of energy.

Happy rotating black hole day!

Anyway, the energy you acquire had to come from somewhere. It came from the black hole, which loses mass and angular momentum via this process.

It does so in a way that prevents the area of the horizon from decreasing, respecting Hawking’s black hole area law.

You can keep doing this for a while, but you get less out of it as the black hole loses mass and angular momentum. Eventually, it spins down and you have a Schwarzschild black hole with less mass than the original rotating black hole.

I am sorry you had to do this your friend, but science requires sacrifice and also the ravenous rotating maw of the dark lord of spacetime demands tribute.

In the late 60s/early 70s, Roger Penrose suggested a mechanism by which energy might be extracted from Kerr’s marvelous rotating black hole.

This is now refered to as the "Penrose Process." It works as follows.

You and a friend venture into the ergosphere. When they aren't looking, you push them towards the horizon. If you arrange things just right, conservation of energy and momentum results in you exiting the ergosphere with more energy than the two of you had going in.