this post was submitted on 08 May 2025
405 points (97.0% liked)

xkcd

10765 readers
128 users here now

A community for a webcomic of romance, sarcasm, math, and language.

founded 2 years ago
MODERATORS
405
submitted 1 day ago* (last edited 1 day ago) by [email protected] to c/[email protected]
 

Title text:

Frankly, given their extreme gravitational fields and general instability, even 12-inch globes should probably be banned.

Transcript:

[A standard globe of the Earth is shown. It stands on a typical stand which holds it by two arms at the poles, so it can turn around like the Earth does. The Earth is turned so it shows Australia at the bottom and most of Asia, including the entire India to the left. Only the very tip of Alaska can bee seen of the Americas. Above the globe there is a double arrow that goes to two small lines that align with the edges of the globe (indicating the diameter). The arrow has been split in the middle and two lines of text is written in the gab. Above this text there is another line of text.]
Remember:
4 inches minimum

[Beneath the globe there are two small drawings. The left shows the Earth and to the left of the Earth there is a double arrow ending at two lines that indicated the diameter of the Earth going from top to bottom. The distance of this is written in inches to the left. From the Earth an arrow points to another drawing, this time the typical depiction of a black hole, with the "hat" shape. A warning sign is shown a the top right of the black hole with an exclamation mark inside.]
7/10"

[Caption Below the Panel:] The Earth's Schwarzschild radius is about 0.35 inches, which is why safety regulations require desktop globes to be at least 4 inches in diameter.

Source: https://xkcd.com/3086/

explainxkcd for #3086

top 20 comments
sorted by: hot top controversial new old
[–] [email protected] 6 points 23 hours ago

That Schwarzschild radius is larger than I expected. I was expecting sub-molecular.

[–] [email protected] 72 points 1 day ago (3 children)

9mm for those wanting sane units. Edit for clarity: this refers to the fractional inches, not the 4 inch figure which, as another poster points out, is a bit north of 10cm.

[–] [email protected] 23 points 1 day ago (1 children)

That's "American" for a round used in a personal protection weapon. So, who is sane now?

[–] [email protected] 3 points 23 hours ago (1 children)

Lmao I knew your username was a familiar sequence to me and I started to say it out loud. Next thing I knew I went full Richard Ayoade with it. 10/10.

[–] [email protected] 2 points 9 hours ago

Goal: Achieved

Hahahaha

[–] [email protected] 9 points 1 day ago

Pfft. There's nothing sane here.

[–] [email protected] 0 points 21 hours ago* (last edited 21 hours ago) (1 children)

Not even close? If you meant CENTImeters then it's closer to 10cm. EDIT: four inches = 10.16 centimeters

[–] [email protected] 2 points 21 hours ago (1 children)

The radius is about .35 inches

Which is 9mm. I have edited my post to indicate this for clarity. I had assumed that "fractional inches" was the part that was least sane and thought others would think the same.

[–] [email protected] 1 points 8 hours ago

as an American i can recognize 9mm because that's the size of a handgun bullet :3

[–] [email protected] 8 points 1 day ago (2 children)

There's also the fact that people might not be able to use it if it's too small.

[–] [email protected] 17 points 1 day ago (2 children)

4" is a respectable size, okay? It's nothing to scoff at.

[–] [email protected] 7 points 1 day ago

It's all about your spin game anyways

[–] [email protected] 3 points 1 day ago

subdued scoffing

[–] [email protected] 3 points 1 day ago

Maybe its less about the size and more about the technique?

[–] [email protected] 9 points 1 day ago (3 children)

Shouldn't 7/10" actually be 7/20"?

[–] vivendi 20 points 1 day ago (1 children)

What in the motherfuck are those numbers

What the fuck is wrong with your units

[–] [email protected] 5 points 22 hours ago

They’re literally called rational numbers

[–] [email protected] 12 points 1 day ago

Notice how the lines the 7/10" is attached to go from one side of the miniature globe to the other? This indicates that measurement is meant to be a diameter. Looking back at the paragraph before he talks about 0.35" being Earth's Schwarzschild Radius. Radius is half of diameter so doubling that radius you get 0.7 or 7/10" across at which the Earth would become a black hole.

That's what that mini diagram is showing.

[–] [email protected] 16 points 1 day ago (1 children)

The same question is in the discussion section in ExplainXKCD, so I can confidently use the reply given there: No, 7/20" is the radius, but 7/10" is correct for the diameter.

[–] [email protected] 2 points 1 day ago

Oh right, didn't pay enough attention. But it was the first thing I saw in the morning.