OK, I’m going to need an explanation for this one.
I have the impression you are going to love the wikiarticle on De Sitter spaces:
I did, and I did not understand a single sentence!
ETA: The [further explanation needed] note is so sweet!
I already tried to read it. Why do you think I asked for help?
Are we talking spherical cow here?
(Pinning for the next xkcd post I might understand)
It’s a riff on the mathematical constructs of De Sitter space and Anti-de Sitter space. They’re multi-dimensional versions of a sphere and a hyperboloid. To explain in very simple terms:
Euclidean space has zero curvature. Think of your basic flat plane. The sum of the interior angles of a triangle will always be exactly 180 degrees.
De Sitter space has positive curvature. Think of your basic spherical surface. The sum of the interior angles of a triangle will always be greater than 180 degrees.
Anti-de Sitter space has negative curvature. Think of the bell of a trumpet or a saddle. The sum of the interior angles of a triangle will always be less than 180 degrees.
Physicists use these things as simplifications of a general metric tensor, where the curvature is not constrained at all.
I read the XKCD explains site, and I still don’t understand it. I wonder if he isn’t just making a joke about how none of the walls in his house are square and parallel, and none of the angles add up correctly.
It certainly describes my house.
I may understand if I let it sit and perk for awhile.
In the meantime, the sign on the door makes me think of Henry Symeonis.
Or some of MC Escher’s work:
No, it’s just that anti-de Sitter space is a funny phrase, because it sounds like it’s against that de Sitter guy, as opposed to the opposite of the mathematical construct he came up with.
Mathematicians love how tractable problems in physics become in anti-de Sitter space; too bad that we’re virtually certain that it isn’t a description of our actual physical universe.
More to the point, de Sitter space and anti-de Sitter space both have a cosmological constant (positive in the former case and negative in the latter), but no matter.
Physicists have a different definition of “to the point” than most people.
“The biggest expense was installing the mantle ducts to keep the carbonate-silicate cycle operating.”
I majored in English. Scribes were always dropping their pages, or just losing their place, and then someone ends up married to his daughter. And it’s not obvious to the next scribe, who tries to retrofit it, by saying that such things used to be common, or that it was really his stepdaughter.
Keep putting new anchors in and after a few hundred million years the NW coast of the US is hundreds of miles further west. I guess you can say that the owners of former shoreline property got screwed.
Yes. But America will be bigger and that’s all that matters. To some people.
“‘Wow, that must be why you swallow so many of them per year!’ ‘No, that’s spiders. You swallow WAY more ants.’”
“After initial tests created a series of large holes in the wall of the lab, the higher-power Scanning Tunneling Tennis Ball Microscope project was quickly shut down.”
“Rümeysa Öztürk was grabbed off the street in my town one month ago.”
Oh wait, this one’s not a joke.
What a fucked up timeline.
Yeah, maybe the least funny XKCD I’ve ever read. 