This is not about spacetime

I originally took this photo illustrating stereographic projection in 2014.
Soon after, someone attached a click-bait caption to the image, and it has been bouncing around the internet ever since. Here, I explain what the image is really about.

I used a Mini Maglite AAA LED Flashlight (in "candle mode") for this video. Cellphone flashlights also work well.

[theskinegg]

I feel like they didn’t make it confusing enough. Consider “the projection of Higgs boson on the quantum manifestation of Albert Einstein’s asshole”

[bsku]

"Hello, I'm Henry Segerman"

That caught me off guard lmfao

[MuzikBike]

Yeah... not sure what they're trying to achieve by spreading this. Props for clearing it up.

[ShakeyBox]

There's no need to lie when this is really cool as it is.

[neologicalgamer]

Holy sh**, it's the actual Henry Segerman

[Sairin]

"Whoa, everything can be mapped in multidimensional geometry. "

"Well, yes, and no, and also it's not as profound as you think, this is just demonstrating mapping between 3d, and 2d, and..."

"But what about the time?"

"Oh, uh, it's about half past five, why?"

[theofficialczex]

I had a friend DM me an image of this with that caption, and I just had to call it on its BS.

[MrJoerT]

Aw nuts. Here I was hoping for a fourth dimensional spacetime, and all I got was an epic demonstration of projection mapping. Are you sure there isn't some extra dimension in there somewhere? Even if you add the word 'quantum' somewhere?

[StruckDuck]

Beautiful work! Replace the light with a camera and the sphere itself would look like a flat plane from that angle. It would be a cool anamorphic illusion!

[HudsonHandel]

I saw that caption on Instagram and decided to subscribe to you on YouTube. I am very glad I did.

[KablamoKelli]

What lightbulb is being used here? I've been trying to do a project like this, but I am having a hard time finding a bright enough and small enough light source.

[jercki]

yeah i was with you with the red "????"

[Rene-uzeb]

Stereo graphic projection is interesting because it allows you to project the whole plane onto a halfsphere, which you then can project back onto a window on the plane by moving farther away from the north pole.
In a computer game, your view is always limited, because the viewer distance to the monitor has to match the virtual scene, so it looks like you are watching through a window, with little view on the left and right. You can widen the viewing angle, but that corresponds to having your nose close to the screen, and if you don’t, everything is distorted.

Modified stereo graphic projection like above allows you to capture a larger viewing angle with less annoying distortions. I did a quick demo worked pretty well.

[Endrushmi]

ah yes. this is how warp drives work. got it!

[nemo-x]

The projection is however a nice visualization of the concept described.

[beensandchees]

Still more accurate somehow than most scientific journalism

[pechaa]

Well done trying to correct the Internet!

[Somerandomjingleberry]

I feel like the idea that people have is the relationship between the projected shadow and the sphere is somehow related to the relationship between our three dimensional spatial reality with some fourth dimension. Which… I can kind of see, but at the same time, feels like a stretch

[OXX]

nah... im seein a lot of fourth dimensional spacetime here

[benjaminwong]

The Caption about spacetime may not be wrong