Today I Learned

[Janus]

That long ago, it should have been Leonardo da Vinci's helicopter?

Not quite that old, but it was a bit small, just a two-seater. https://en.wikipedia.org/wiki/Piper...:Piper_PA-38_Tomahawk_3-view_line_drawing.svg
The flight instruments were basic and not much in the way of avionics. ( basically a VOR and a Radio) No headset either, you used a handheld mike. What gave it its reputation was its stall characteristics. Unlike most small aircraft, it needed the pilot to apply correction, and if you waited too long, you'd enter an unrecoverable spin.

 

[Hornbein]

TIL I learned that while President Teddy Roosevelt suffered permanent partial loss of sight during boxing practice, possibly due to a detached retina. Each account I read gave a different name for the sparring partner involved. TR had been a wimp as a boy and elected to toughen himself up through rough exercise, was a cowboy for a while, and so forth. He tried to lead an army of volunteers into World War One.

TR died quite suddenly and unexpectedly in his sleep from a blood clot detaching and lodging "in his lungs."

 

[Hornbein]

Today I learned that in the old days collisions of obsolete trains were arranged. Such attracted huge crowds, in one case so many that a temporary town was constructed for the tourists.

https://en.wikipedia.org/wiki/Crash_at_Crush

 

[DaveC426913]

TIL this is not a typo. You Brits really spell it like this. Weirdos...

Byyeeeeee!

 

[Hornbein]

Today I learned that in the old days collisions of obsolete trains were arranged. Such attracted huge crowds, in one case so many that a temporary town was constructed for the tourists.

https://en.wikipedia.org/wiki/Crash_at_Crush

This brings up a physics question. Why did the boilers explode in this particular crash? That had never happened before.

Spoiler

My explanation is that the two trains were the same weight and speed. Usually there is some difference and the dominant train knocks the other out of the way. In the Crash case the parties were equal so the two engines accordioned. No metal can withstand this.

I am reminded of the traditional alphabet of Java and Bali. The eighteen letters are ordered in such a way as to be a poem. In English translation it is

There were messengers
Had a dispute
Equally powerful
Both died

I defy the world to find a more obscure yet apt analogy.

https://en.wikipedia.org/wiki/Balinese_script

 

[jack action]

TIL that kilo comes from a different spelling of chilioi, derived from the Greek word χίλιοι, meaning thousand.

 

[mayflowers]

TIL that batteries create a dipole which makes a current readily available, and that the battery dies over time because of being hooked up into a closed circuit.

I always thought rechargeable batteries were a brilliant idea. Glad they are very common now.

 

[DaveC426913]

TIL: "The US uses metric, they just disguise it. All* US standard units are defined in terms of metric units, and have been since the 19th century. For example, an inch is *defined* as 0.0254 meters in the US. Whenever the SI system gets updated, the US system gets updated as well."

Indeed, the Imperial inch is defined as 25.4mm.


*have not verified.

 

[sbrothy]

... That Captain Arthur Phillip, around 1787, was tasked with thinning out the British underclass by sailing 1500 petty criminals (one stole 12 cucumber plants, another pocketed a book called "A Summary Account of the Flourishing State of the Island of Tobaco") on a one way trip to Australia, which had only been visited by Europeans once many years before. The journey took 252 days (eight months) and covered 15000 miles of open sea (more than was strictly neccessary, but they crossed the Atlantic in both directions to catch favorable winds).

Ironically, thinking of their misdemeanors, this was an age were you could be hanged for any of 200 acts, including, notably, "impersonating an Egyptian"(?!).

So I guess it was a merciful alternative all things considered.

 

[jack action]

TIL

An imaginary number raised to an imaginary power can give a real number.

For example:
i^i \approx 0.2078

At first, this feels completely wrong. Imaginary numbers already seem “not real,” so how can raising one to another imaginary power suddenly give a normal real number?

The answer comes from Euler’s formula, which connects exponential functions with trigonometry. In simple terms, complex numbers behave in a circular way, and when you raise them to powers, they rotate and shrink or grow in a very structured pattern.

When you apply this idea to i^i, all the imaginary parts cancel out in a surprising way, leaving behind a real number: about 0.2078.

Even more interesting: this is just one value. Because of how complex logarithms work, i^i can actually have multiple real values depending on how you define the angle!

Math is full of these strange but beautiful results—things that look impossible at first, but turn out to be perfectly true once you understand the deeper rules.

 

[Demystifier]

Today I learned that Terry Rudolph, the R from the famous PBR theorem, is a grandson of Erwin Schrodinger and his mistress. https://en.wikipedia.org/wiki/Terry_Rudolph

 

[Hornbein]

Today I learned that Terry Rudolph, the R from the famous PBR theorem, is a grandson of Erwin Schrodinger and his mistress. https://en.wikipedia.org/wiki/Terry_Rudolph

Erwin, the mistress, and his wife shared a house. It was a harem.

William Marston, the creator of Wonder Woman, had a similar arrangement.

 

[DaveBeal]

TIL two things about the geometry of curved surfaces: (1) There are no similar triangles on a curved surface, because making a triangle bigger causes its angles to change, and (2) on a surface of constant negative curvature K, a triangle's area can never exceed -π/K.

 

[Hornbein]

Today I learned the actor Chevy Chase was the first drummer with Donald Fagan and Walter Becker, later known as Steely Dan.

 

[mayflowers]

TIL, cymatics is the visualization of sound vibrations in geometric patterns

 

[symbolipoint]

TIL, cymatics is the visualization of sound vibrations in geometric patterns

I made a quick search DDG and found and read first sentence or two of the Wikipedia article. The description reminds me of Chladni patterns.

edit: I should have read a little further first. The article does mention or refer to Chladni patterns.

 

[mayflowers]

I made a quick search DDG and found and read first sentence or two of the Wikipedia article. The description reminds me of Chladni patterns.

edit: I should have read a little further first. The article does mention or refer to Chladni patterns.

There's actual equations for this type of phenomenon??

That is.. so cool.

 

[Hornbein]

Today I learned that commercially sold teak oil contains no teak oil.

 

[Jonathan Scott]

Today I learned that commercially sold teak oil contains no teak oil.

Isn't that simply because it's oil for using on teak, not oil from teak?

 

[symbolipoint]

Today I learned that commercially sold teak oil contains no teak oil.

Sure! Teak oil is a blend of oils applied to protect teak wood. Looking further, you may find notations saying that the blend of oils could also have some solvents included.

https://www.teakmaster.com/blog/teak-oil-what-is-it-and-how-do-i-use-it/

 

[DaveC426913]

Today I learned that commercially sold teak oil contains no teak oil.

Wait'll he hears about baby oil...

 

[DaveC426913]

TIL that bringing your boat to your mechanic is like going to your doctor. You take off all your clothes in front of a stranger and they see you at your worst.

He: :peers into every dark hole and cubby, makes disapproving noises:
Me: "Yeah, I'm getting that taken care of. It's been a rough winter."

He: "This here is not good. Do you want me to fix that?"
Me: "Never mind that. That's not why I came here. I'll take care of it myself."

He: :strokes chin: "Has this leak always been here?"
Me: "Yeah, I meant to clean that up before coming to see you."

He: "And the smell?"
Me: "I was in a hurry!"

He: "Marg, cancel my next few appointments please."

 

[sbrothy]

Maybe somone remember that I posted that I learned about enteral respiration and that turtles (and other animals) can breathe through their butt. Now it's not that 'm fixated on butts, but I guess ayone would say that.

Anyway, today I learned that baby giraffes sleep using their butt as a pillow. It looks really cute:

Look how cute giraffes are when they sleep (hint: they use their butt for a pillow)

 

[Swamp Thing]

As a teenager, I developed this spergy skill of slowing down a classic balance wheel type alarm clock by rotating it clockwise and anticlockwise in the palm, finally 'whispering' it down to a dead stop.

Today I Learned that a similar phenomenon is called "Amplitude Death" in the field of coupled nonlinear dynamical systems.

Technically, my example was not quite an amplitude death phenomenon because the influence wasn't mutual, and I am therefore still here to type this post decades later

 

[DaveC426913]

spergy

TIL.

 

[Swamp Thing]

I just learned, furthermore, that my case could perhaps be an example of "Oscillation Death" rather than "Amplitude Death". Or an example of some third category where asymmetry is baked into the system to start with.

For other spergy folk among you:
https://share.google/aimode/n1yOozhgBa28FkIbp
(please scroll up to get to the beginning of the chat. Annoyingly, the default is to show you the
last response).

 

[gmax137]

TIL.

Me too

 

[sbrothy]

I just learned, furthermore, that my case could perhaps be an example of "Oscillation Death" rather than "Amplitude Death". Or an example of some third category where asymmetry is baked into the system to start with.

For other spergy folk among you:
https://share.google/aimode/n1yOozhgBa28FkIbp
(please scroll up to get to the beginning of the chat. Annoyingly, the default is to show you the
last response).

I had to look up "spergy" to really understand what you're talking about. So, TIL a new word and some context.

 

[Swamp Thing]

I had to look up "spergy" to really understand what you're talking about. So, TIL a new word and some context.

I am 65 now, and I never had a life from my clock-stopping days till today.

 

[sbrothy]

I am 65 now, and I never had a life from my clock-stopping days till today.

Ouch. I'm "only" 50 but yeah time is a harsh mistress!