Today I Learned

[Drakkith]

TIL of the most extreme software optimization example I've ever come across.
Matt Parker from Stand-up Maths created a program in python to look for groups of 5 words that share no letters between them, meaning that each letter in the alphabet will be used one time only, leaving a single letter unused. His program was improved by over 40 BILLION percent by users, going from a run-time of about a month to less than 10 milliseconds. (The percentage graphic in the beginning of the video states an incorrect percentage. Matt explains in the video description that the 40 billion percent number is the correct one.)

 

[BillTre]

On this day in 1886 (136 years ago), the Statue of Liberty was dedicated.

 

[fresh_42]

On this day in 1886 (136 years ago), the Statue of Liberty was dedicated.

Always reminds me of what I had read in a book about American history (pop science):

... but the French are pranksters. She's hollow inside!

 

[DaveC426913]

Always reminds me of what I had read in a book about American history (pop science):

... but the French are pranksters. She's hollow inside!

And by night, a phalanx of mimes comes pouring out!

 

[fresh_42]

And by night, a phalanx of mimes comes pouring out!

Fernau's comment was meant to be quite ambiguous.

 

[Hornbein]

Today I learned that radiation from black hole accretion discs is mostly "soft thermal." So if one should fall inside of a black hole's event horizon, it's dark in there.

 

[epenguin]

What will you see in your presumably short (whatever that means) lifetime there? E.g. some black holes millions or billions of light years away? maybe someone who learned before today knows.

 

[BillTre]

Some pumpkins age better than others.

 

[Swamp Thing]

TIL that Winston Churchill said, "We know it will be hard; we expect it to be long".

Spoiler

He meant the war.

Spoiler

Of course.

 

[BillTre]

TIL that Winston Churchill said, "We know it will be hard; we expect it to be long".

Spoiler

He meant the war.

Spoiler

Of course.

Ukraine is in a similar situation these days.

 

[Hornbein]

What will you see in your presumably short (whatever that means) lifetime there? E.g. some black holes millions or billions of light years away? maybe someone who learned before today knows.

I would see no light in my direction of motion. Some light behind, which would shrink into a dot. Gravity would focus the light, which would make it brighter. On the other hand the dot is red shifted and there isn't that much hard radiation around so the light grows dimmer for that reason.

 

[epenguin]

Gravity would focus the light? On me? That's a surprise – surely I am not so attractive? Gravitationally.

 

[BWV]

The scary pace of AI advancements must mean the singularity is nigh

 

[BWV]

Spoilers for James Cameron's Avatar sequel got leaked out on the internet:

https://en.wikipedia.org/wiki/Pocahontas_II:_Journey_to_a_New_World#Plot

 

[symbolipoint]

Tell us how you created that spoiler which is blurry initially and turns focused when left-clicked?

 

[berkeman]

Tell us how you created that spoiler which is blurry initially and turns focused when left-clicked?

Looks like he used [ ISPOILER ] [ /ISPOILER ] tags (without the spaces)...

 

[jbriggs444]

Tell us how you created that spoiler which is blurry initially and turns focused when left-clicked?

You mean the [ispoiler] and [/ispoiler] tags?

Edit: When in doubt, use the Reply button to get the entire post in as a quote in your post window and inspect the tags therein. You can also use the "[ ]" (toggle BB code) icon if needed.

Edit 2: In order to avoid having to put blanks around your BB code to neuter it so that it does not render, one can use [PLAIN] and [/PLAIN] around the tags that you want to leave unrendered.

 

[DrGreg]

Tell us how you created that spoiler which is blurry initially and turns focused when left-clicked?

 

[pbuk]

Edit 2: In order to avoid having to put blanks around your BB code to neuter it so that it does not render, one can use [PLAIN] and [/PLAIN] around the tags that you want to leave unrendered.

Ooo, when was that introduced? You mean we don't have to use the [ hack any more?

 

[fresh_42]

Ooo, when was that introduced? You mean we don't have to use the [ hack any more?

The plain tags do not work. See:

$2+2=4\text{ without tags}$
$2+2=4\text{ with tags}$

 

[pbuk]

The plain tags do not work. See:
$2+2=4$

$2+2=4$

You have to be more subtle than that to defeat MathJax: $2+2=4$.

 

[pbuk]

You have to be more subtle than that to defeat MathJax: $2+2=4$.

Oh, even more subtle (of course, BBCode tags are processed on the server, MathJax runs in the browser). Need to revert to the color hack: ##2+2=4#[/color]#.

 

[berkeman]

You people talk funny...

 

[fresh_42]

Oh, even more subtle (of course, BBCode tags are processed on the server, MathJax runs in the browser). Need to revert to the color hack: $2+2=4$.

There is one opportunity where it might work: ##\mathbb{C}\cong \mathbb{R}.$Let's test it:$\mathbb{C}\cong \mathbb{R}[i]$although I think I will stick with the blanks:$\mathbb{C}\cong \mathbb{R}[ i ].## Is shorter. Nope.

 

[fresh_42]

Maybe the other way around, i.e. putting the misinterpretation at the end for a real test:

Oh, even more subtle (of course, BBCode tags are processed on the server, MathJax runs in the browser). Need to revert to the color hack: $2+2=4$.

There is one opportunity where it might work. Let's test it: $\mathbb{C}\cong \mathbb{R}[i]$ although I think I will stick with the blanks: $\mathbb{C}\cong \mathbb{R}[ i ].$ Is shorter. Nope. Yeah!

Edit: It works in that case! The PLAIN tag guarantees that ##\mathbb{R}## (color hack here) isn't misinterpreted!

Edit Edit: Color hack failed.

 

[pbuk]

In summary, here is what you need to do:

• To display BBCode as "plain", just wrap it in [PLAIN][/PLAIN] tags.
• This doesn't work for displaying the [/PLAIN] tag itself so to display you still need to use the color hack: [PLAIN][/PLAIN]
• Note you can also use the [ICODE] or [CODE] tags to display BBCode tags, this even works for [PLAIN] e.g.

  [ICODE][PLAIN][/PLAIN][/ICODE]

• To display MathJax expressions contining BBCode tags e.g. [i] you need to wrap the whole expression with [PLAIN][/PLAIN] tags.
• If you want to display MathJax tags themselves (i.e. ## or $$) then you need to use the color hack to split up the tags as well as the plain tags inside them if necessary to protect e.g. [i]
  

  ##[PLAIN] \mathbb{C}\cong \mathbb{R}[i] [/PLAIN] ##

Or just don't bother and save an hour of your life.

 

[mfb]

Some simpler options:

To display the plain tag you can break it up with plain tags or any other tag: [pla[plain][/plain]in] / [pla[b][/b]in] -> [plain]

If you have [i] in TeX you can write it as [ i] or similar - TeX won't care and the forum will stop interpreting it as BBCode: $[/color]a[ i]$[/color] -> $a[ i]$

One color tag is enough to break up MathJax tags: $[/color]a^3$[/color] -> $[/color]a^3$

 

[pbuk]

To display the plain tag you can break it up with plain tags or any other tag: [pla[plain][/plain]in] / [pla[b][/b]in] -> [plain]

Good point, much better.

If you have [i] in TeX you can write it as [ i] or similar - TeX won't care and the forum will stop interpreting it as BBCode: $[/color]a[ i]$[/color] -> $a[ i]$

That looks awkward, I think the new "plain" tag is better.

0
One color tag is enough to break up MathJax tags: $[/color]a^3$[/color] -> $[/color]a^3$

That will break if there is more than one section of $\LaTeX$ as MathJax will try to process the text between the two unobfuscated tags.

 

[collinsmark]

Ooo, when was that introduced? You mean we don't have to use the [ hack any more?

I remember that, from back in the day.

Of course it wasn't (0,0,0) though, it was whatever PF's background happened to be at the time. That was what we did before Greg got spoiler tags. (Or if we wanted special punctuation like indenting paragraphs.)

The idea is that you had to take your mouse and drag across the text -- highlighting it -- and then you could
read it.

Something like this (take your mouse or finger or whatever and drag it over the line below):
I can see!
But even that might not work (it might already be visible, without highlight it), depending on your browser settings. (This example used [249, 249, 249].)

 

[jbriggs444]

This doesn't work for displaying the [/PLAIN] tag itself so to display

You do not need a hack to display [/PLAIN]. In the absence of a [PLAIN] opening tag, the closing tag will not render and will be displayed verbatim instead.