Today I Learned

[BillTre]

Another weird 2020 thing:
Today I learned 2020 now has a Zombie Tropical Storm.

Zombie tropical storms are when a tropical storm becomes weak, drops out of thee tropical storm category due to its loss of strength, but then gets stronger and becomes a tropical storm again.

 

[Swamp Thing]

Today I learned that vanilla is an orchid -- the only edible orchid, actually.

 

[collinsmark]

https://phys.org/news/2020-09-astronomers-earth-sized-pi-planet-day.html

But is it 3.14 Earth days or 3.14 times its own day? If the latter, then any alien intelligent being would notice this curious fact, too.

Our days. Rotation periods are very difficult to measure and astronomers wouldn't write days then.

Yeah, I understood that it's almost certainly Earth days. And a planet orbiting a star that close to it is usually tidally locked, as far as I know (not being a specialist in this).

We can do the math to see if it's at least in the ballpark!

The key sentences are:

It orbits a cool, low-mass star that is about one-fifth the size of the sun. The planet circles its star every 3.14 days, at a blistering 81 kilometers per second, or about 181,000 miles per hour.

That all the info one needs to calculate the period. The following equations could prove useful:

Centripetal force equals gravitational force (assuming a circular orbit):

\frac{v^2}{r} = G \frac{M}{r^2}

We're not given what r is. But we're not looking for r, we're looking for the period T. And we know

v = \frac{2 \pi r}{T}

Solve for T. According to my calculations, if M is just a bit lighter than \frac{1}{5} the mass of the Sun, the period is at least somewhere in the ballpark of the claimed 3.14 Earth days.

 

[hilbert2]

Found something to compare this to:

The exoplanet Gliese 581b has a mass of 15.8 times Earth and its orbital period is about 5.4 Earth days. The orbit radius is 0.041 AU, much less than even that of Mercury. The next closest planet orbiting that star, Gliese 581c, is said to be almost certainly tidally locked because even it is so close to the star. I'm not sure if the 581b is a gas planet and whether that prevents tidal locking, but otherwise it should be tuned to rotate in that way too.

 

[Keith_McClary]

TIL

 

[mfb]

I didn't learn it today, but I never saw the connection until today:

In English, if you don't care about something you can say you don't give a sh*t.
In German, if you don't care about something you can say "Scheiss drauf", which translates literally to "sh*t on it".

Same meaning, completely opposite phrase.

 

[Tom.G]

TIL a new word, "abseiling."
Used by @Astronuc in post:
https://www.physicsforums.com/posts/6400047/

Google says; British: ... descending a rock face or other near-vertical surface by using a doubled rope coiled round the body and fixed at a higher point.

 

[Astronuc]

TIL a new word, "abseiling."
Used by @Astronuc in post:
https://www.physicsforums.com/posts/6400047/

Google says; British: ... descending a rock face or other near-vertical surface by using a doubled rope coiled round the body and fixed at a higher point.

It was new to me too, since I don't rappel or rope climb very often. The word is derived from German verb abseilen, to rope down, or lower by rope, or rappel. One can also use 'sich abseilen'.

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

 

[DrGreg]

It was new to me too, since I don't rappel or rope climb very often. The word is derived from German verb abseilen, to rope down, or lower by rope, or rappel. One can also use 'sich abseilen'.

TIL a new word "rappel". It means "abseil".

Strange how some words don't travel. "Abseil" is well-known (to the general public) in the UK, but "rappel" isn't.

 

[Astronuc]

TIL a new word "rappel". It means "abseil".

Strange how some words don't travel. "Abseil" is well-known (to the general public) in the UK, but "rappel" isn't.

When I saw the word, I figured that it must have German origin. Rappel has a French origin.

https://www.etymonline.com/word/rappel
https://en.wikipedia.org/wiki/Australian_rappel

I was also surprised by the note on the Wikipedia page about Abseiling: "This article may lend undue weight to certain ideas, incidents, or controversies." Seriously?!

I would have thought Aussie rappelling, or abseiling, would be doing it upside down.

 

[fresh_42]

TIL a new word, "abseiling."
Used by @Astronuc in post:
https://www.physicsforums.com/posts/6400047/

Google says; British: ... descending a rock face or other near-vertical surface by using a doubled rope coiled round the body and fixed at a higher point.

The German word is "abseilen". ab for down and seil for rope. We also use it if we want to leave a place secretly, e.g. leaving a party or meeting early, in which case it is used reflexive: sich abseilen = to abseil oneself.

 

[DrGreg]

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

I would have thought Aussie rappelling, or abseiling, would be doing it upside down.

I've just read the Wikipedia article, and they do do it upside down, i.e. facing downwards and away from the rock face or building, the opposite of what I understood as "abseiling".

 

[Astronuc]

We also use it if we want to leave a place secretly, e.g. leaving a party or meeting early, in which case it is used reflexive: sich abseilen = to abseil oneself.

As opposed to "sich aufseilen" = to pull oneself up by rope?

 

[fresh_42]

As opposed to "sich aufseilen" = to pull oneself up by rope?

Never heard before, but it's in the dictionary.

 

[mfb]

I was also surprised by the note on the Wikipedia page about Abseiling: "This article may lend undue weight to certain ideas, incidents, or controversies." Seriously?!

Here is the explanation. The user who added that template argues that rappelling is more widely used and should be preferred.

I never heard "aufseilen" before either.

 

[fresh_42]

I never heard "aufseilen" before either.

I suppose neither of us knows some of these guys:

 

[Ibix]

Some cichlids eat the scales off of other cichlids as a major nutritional component. They have a handedness to their mouth so they specialize in eating scales from one side of their prey.

Today I learned that there are asymmetric fish that specialise in eating from one side of their prey.

 

[BillTre]

Here's another weird one: Anableps

They are asymmetrical in their sexual organs: they are live bearers (don't lay eggs, give birth to little fish) and therefore require internal fertilization.
The male has a specialized fin which acts like a penis to transfer sperm, as required for internal fertilization.
In Anableps, their body geometry (presumably, their more round in cross section then many other live bearers) drives the specialization of mating from one side or the other, but not both.

Additionally, they are known as "four eye fish" because each of their two eyes are divided horizontally.
Each different properties; one for looking under water (like normal fish), one for looking through the air from their poked out of the water position, for threats from above.
These fish live in shallow brackish water shores, like beaches/mudflats.
They are prey for birds flying over, so they have to aware of them --> in order to, through intentional movement, avoid predation.
They seem to be constantly in rapid motion.

They will go under water, but prefer to be at the top with their eyes poking out.

 

[Keith_McClary]

TIL about bilateral gynandromorphy in Pheucticus ludovicianus

while one side of the rose-breasted grosbeak appears genetically female, the other side shows all the hallmarks of a genetic male.

 

[ishika17]

Today I learned about amazing facts that Green Chemistry is resulting in.and It is actually turning Oranges to plastic!
http://advancinggreenchemistry.org/... explained in,the carbon dioxide they produce.

 

[hilbert2]

You can make a tube lamp light up a bit by taking the voltage from several 9 V batteries connected in series, but you probably don't want to combine enough batteries to equal the intended voltage.

 

[Tom.G]

...several 9 V batteries connected in series...

Please define or approximate "several."

 

[hilbert2]

Please define or approximate "several."

Even one battery will make it produce some light, two or three a bit more.

 

[Swamp Thing]

but you probably don't want to combine enough batteries to equal the intended voltage.

You could always put a resistor in series.

Would about 50 volts be enough to see some glow? If so, you could safely let the current pass through you from fingertip to fingertip. (Umm, maybe not if you have any kind of heart condition). Or, you and a couple of friends could join hands to form the circuit... a modern version of those 18th century electrostatic parlor tricks.

You could even combine it with some Victorian occultism and, ah, "conduct" an electric séance.

 

[Keith_McClary]

You can make a tube lamp light up a bit by taking the voltage from several 9 V batteries connected in series

This page suggests you need hundreds of volts if you don't preheat the electrodes.

There is an LED replacement.

 

[mfb]

Would about 50 volts be enough to see some glow? If so, you could safely let the current pass through you from fingertip to fingertip.

• Not advisable in terms of safety
• it would limit the current so much that you won't see anything.

 

[hilbert2]

This page suggests you need hundreds of volts if you don't preheat the electrodes.

There is an LED replacement.

As far as I know, the longer bathroom tube lamps often have this kind of "igniter" at one end to start the current flow.

 

[Tom.G]

Since that is a 2-pin device it is called a Starter (in the US), it is a Normally Closed thermal switch that connects power to the filaments (heaters) in the tube. This vaporizes some of the Mercury in the tube, which is the main conductor during operation.

After a few seconds, the Starter heats up enough to open, removing power from the filaments and applying the high voltage across the ends of the lamp. The high voltage is sufficient to ionize the the Mercury vapor and other gasses in the tube to a plasma, thus emitting UltraViolet light.

The UV light excites the phosphors coating the inside surface of the tube to emit visible light. Different combinations of phosphors are used for different Color Temperatures such as Warm White, Cool White, Daylight, etc.

There are also Instant Start lamps and circuits that do not need a Starter or an Ignitor.

Cheers,
Tom

 

[etotheipi]

TIL that the empty set $\varnothing$ is a function!

 

[DaveE]

TIL: A Butt is (ok, was) a real unit of measure. 1 Butt ≈ 500 litres of wine. So drinking a Butt-load of wine probably isn't a great idea.

 

[Keith_McClary]

So drinking a Butt-load of wine probably isn't a great idea.

Not at one sitting, anyway.
A butt is half a tun.

 

[strangerep]

A butt is half a tun.

Must... resist... temptation to post pictures of certain celebrities as confirmatory evidence of this...

 

[Janus]

TIL: A Butt is (ok, was) a real unit of measure. 1 Butt ≈ 500 litres of wine. So drinking a Butt-load of wine probably isn't a great idea.

a Butt-load of Beer would be worse, as there are two hogsheads to a Butt and a hogshead of beer is 64 gallons, vs. 63 gallons for wine. ( imagine the trips to the restroom!)

 

[strangerep]

TIL... "de Broglie" is pronounced "de Broy" (rhymes with destroy). [Thanks to Sabine Hossenfelder's latest video.]

But,... WTF?? How do you get "oy" out of "oglie".

Oh well, English can be incomprehensibly weird too, at times.

 

[DaveE]

TIL... "de Broglie" is pronounced "de Broy" (rhymes with destroy). [Thanks to Sabine Hossenfelder's latest video.]

But,... WTF?? How do you get "oy" out of "oglie".

Oh well, English can be incomprehensibly weird too, at times.

Because it's not English. He was French.

 

[mfb]

But,... WTF?? How do you get "oy" out of "oglie".

I'll tell you after you tell me how you get 10 different sounds out of "ough".
rough, through, thorough, borough, cough, bough, thought, hiccough, ...

The French love to write a few more letters than they pronounce at the end of words.

 

[mfb]

TIL about thr Conway base 13 function.

The intermediate value theorem says that a continuous function will reach every intermediate value between f(a) and f(b) somewhere between a and b. But is the converse also true? Is a function that reaches every intermediate value (for any a,b) continuous? No, and the above function is a counterexample.

 

[Tom.G]

With just a quick read of the Wikipedia article, it looks like that assertion is a fallacy.

They are redefining some characters that are numeric in base 13 (specifically "+", "-", ".") as operators or delimiters in base 10.

As an example the American word 'Corn.'

(following extracted from:
https://forum.thefreedictionary.com/postst137875_Maize-Vs-Corn.aspx)

Maize is big green leafy plants with yellow cobs.
In America this is called corn.
.
.
In the UK, that is called maize, but the vegetable on the stalk is called corn on the cob,
.
.
In the UK, corn is a grain.
It commonly means wheat, but it can apply to any grain.Or... maybe I missed something?

 

[mfb]

They are redefining some characters that are numeric in base 13 (specifically "+", "-", ".") as operators or delimiters in base 10.

It's just a way to describe how the function assigns values to numbers. To find f(a), write a in base 13, replace A B C with symbols, then assign f(a) based on the described algorithm. Where is the problem?

I don't see how this would have anything to do with the way corn is described in English.

 

[Tom.G]

Yup,

I missed something?

I read only thru the "Sketch of definition" section. Reading the rest of the article, you are probably correct. I'll go to bed now.

Goodnight.

 

[fresh_42]

TIL that cheetahs were originally american cats who emigrated to Africa.

 

[BillTre]

TIL that Tom Lehrer (yes, he's still alive) has released all his compositions from copyright.

 

[Keith_McClary]

TIL the Large Hadron Collider has a beam lifetime (time interval after which the intensity of the beam has reached 1/e of its initial value )of

Spoiler

ten hours.

Source.

 

[DaveE]

TIL the Large Hadron Collider has a beam lifetime (time interval after which the intensity of the beam has reached 1/e of its initial value )of

Spoiler

ten hours.

LOL. I was thinking femtoseconds! Clearly I have NO IDEA AT ALL how this machine works.

 

[jbriggs444]

LOL. I was thinking femtoseconds! Clearly I have NO IDEA AT ALL how this machine works.

The main loop is 26 kilometers. At 300,000 km per second, that's about 10 laps per millisecond. You need your beam line particles (a substantial fraction anyway) to survive for at least a couple of laps, otherwise you might as well build a linear accelerator instead.

Surviving for 10 hours -- 360 million laps if I haven't slipped a digit -- is impressive. [Of course I doubt you would keep the same particles in the beam that long. The quoted figure is likely just extrapolation from the loss rate you get for the short intervals you actually use]

Caveat: I'm not an expert, just applying high school physics knowledge to the situation.

 

[mfb]

Collisions with the opposing beam are indeed an important loss mechanism, and of course it's one you do not want to reduce.

Refilling the LHC takes at least two hours but three hours is more typical (and four to five can happen, too), so this long lifetime is important. The optimal time to dump the beam and refill comes after about 15 hours.

 

[Astronuc]

Some railroad trivia

1961: Missouri Pacific acquires the rail industry’s first solid-state computer, an IBM 7070. Railroads will become one of the earliest major users of computer technology.

1968: Southern Pacific acquires the rail industry’s first locomotive engineer training simulator.

1970: In June, the giant Penn Central declares bankruptcy. At the time, it was the biggest corporate bankruptcy in U.S. history. I remember that day. It precipitated the bankruptcy of many other railroads in the NE US, including the Lehigh Valley, Erie Lackawanna, Reading, Central of New Jersey, Lehigh and Hudson River and the Pennsylvania-Reading Seashore Lines.
https://en.wikipedia.org/wiki/Penn_Central_Transportation_Company#Bankruptcy

The Penn Central Transportation Company was created in 1968 via a merger between the Pennsylvania and New York Central railroads. The Pennsylvania Railroad dated back to 1846, and the New York Central railroad dated back to 1853.​

https://finance.yahoo.com/news/day-market-history-penn-central-180215022.html​

1976: The Railroad Revitalization and Regulatory Reform Act creates the Consolidated Rail Corp. (Conrail) from six bankrupt Northeast railroads. The legislation also includes regulatory reforms that are supposed to make the rail regulatory system more responsive to changed circumstances.

1977: The Chicago, Milwaukee, St. Paul and Pacific Railroad (CMStP&P), aka the "Milwaukee Road" (reporting mark MILW) filed for its third bankruptcy in 42 years on December 19. It suffered from poor management for about 7+ decades. Operations ended west of Miles City, Montana on February 29, 1980. Ultimately, lines were abandoned and the surviving railroad broken up and sold to Soo Line (a subsidiary of CP), BN (now BNSF), and other smaller railroads.​

https://en.wikipedia.org/wiki/Chicago,_Milwaukee,_St._Paul_and_Pacific_Railroad#Early_1970s​

The BN was formed in 1970 from the merger of Great Northern; Norther Pacific; Chicago, Burlington & Quincy (CBQ) and Seattle, Portland & Spokane (SPS)​

https://en.wikipedia.org/wiki/Burlington_Northern_Railroad#History​

The Milwaukee Road secured concessions from the BN merger, which were intended to preserve competition in the Norther States and Pacific Northwest. However, MILW failed to ensure the concessions were met, and the ICC failed to enforce, in addition to having a rundown physical plant.​

1980: Congress passes the Staggers Rail Act, reducing the Interstate Commerce Commission’s regulatory authority over railroads and sparking competition that stimulates advances in technology and a restructuring of the industry, including creation of hundreds of new shortline and regional railroads using rail lines spun off from larger railroads.

During the 1980s, the railroad industry began a merger trend that now sees essentially 7 class I freight railroads: BNSF and UP in the west, CP, CN and KCS in the middle and north, and CSX and NS in the east.​

1996: After 108 years, the Interstate Commerce Commission goes out of existence and is replaced by the Surface Transportation Board, which assumes responsibility for remaining regulation of rail rates and services.

2008: Coal again becomes the top source of U.S. rail industry revenue, overtaking intermodal (which had taken over the top spot in 2003). Class I railroads originate a record 879 million tons of coal.

https://www.aar.org/chronology-of-americas-freight-railroads/

In 2020, coal shipments have dropped about 17% from 2019 levels and about 30% from 2018 levels.​

 

[Borg]

TIL about Chaos Engineering and the Simian Army.

 

[DaveE]

TIL how to write unmaintainable code. Y'all have probably seen this, but it's new to me and HILARIOUS.

A couple of randomly chosen excerpts:

Åccented Letters
Use accented characters on variable names, e. g.
typedef struct { int i; } ínt;
where the second ínt’s í is actually i-acute. With only a simple text editor, it’s nearly impossible to distinguish the slant of the accent mark.

Reuse of Global Names as Private
Declare a global array in module A and a private one of the same name in the header file for module B, so that it appears that it’s the global array you are using in module B, but it isn’t. Make no reference in the comments to this duplication.

 

[Borg]

The Bedazzling Names part of the Naming section has always been my favorite.

Choose variable names with irrelevant emotional connotation, e. g.:

marypoppins = ( superman + starship ) / god;

This confuses the reader because they have difficulty disassociating the emotional connotations of the words from the logic they’re trying to think about.