Today I Learned

[DaveC426913]

I had no idea that Curly was already dead a decade before I was even born

Curly's Pants by Corky and the Juice Pigs

They were the pants that Curly died in
They were the pants he could not hide in
And they had a button fly
And they poked me in the eye (Whadja do that for?)
And it was my defeat
When I wore them on the street
'Cause I would go
(Whoop Whoop whoop whoop!)

 

[berkeman]

TIL that MotoGP riders have airbags in their leathers that activate during crashes to add protective padding to their upper body parts. I only found out about it because apparently one of the riders in last weekend's Australian Gran Prix race had his airbags go off accidentally due to some violent shaking of the bike coming out of a turn. He said it was awkward trying to ride while feeling like the Michelin Man, all extra puffy. It took about a lap for the air bags to fully deflate for him.

https://www.autosport.com/motogp/news/safety-devices-in-motogp-airbags-helmets-boots/6438518/

Airbag

The most complex of these is the airbag, which has been used in MotoGP for years but finally became mandatory in 2018. It is positioned around the back, shoulders and rib cage inside the suit, and is designed to absorb the forces endured by riders when they fall off their bikes.

Race suits are fitted with accelerometers, gyroscopes and a GPS, and the airbag is activated when sensors detect that a fall has occurred. The software is very clever and can tell the difference between a genuine incident and a near miss, so inflation doesn’t occur at random.

Two gas canisters are secreted inside the suit, and when the system detects a fall the chambers of the airbag fully inflate in just 25 milliseconds; about a quarter of the time it takes to blink. They stay inflated for around five seconds, by which time a rider will usually have come to a stop.

 

[pinball1970]

Still pretty confused by the whole Bell thing.

In order to get a grasp on what Clauser and the others did you have to understand Bell and to understand Bell you have to understand EPR and a few bit and pieces inbeween.

(thanks guys for the links papers and videos- I am still working through them)
One thing I absolutely do not understand is the political part to it.

When Bell came up with a way to test the EPR why did he not shout it from the roof tops in 1964?

It was an answer to the Einstein Bohr debate how could it not be important? He worked at CERN and did not tell his colleagues about the paper

When Clauser started researching to test Bell in the late 60s early 70s why was he discouraged? He was told it would ruin his career.

One quote was from Feynman, “Quantum physics is right!” Why are you even looking??

They did not actually know about hidden variables though did they?

How could this be a non-issue?

 

[WernerQH]

When Bell came up with a way to test the EPR why did he not shout it from the roof tops in 1964?

It was an answer to the Einstein Bohr debate how could it not be important? He worked at CERN and did not tell his colleagues about the paper

When Clauser started researching to test Bell in the late 60s early 70s why was he discouraged? He was told it would ruin his career.

Generations of physicists have struggled to understand quantum theory. (And they still do!) There was a general atmosphere of frustration, and most physicists succumbed to Bohr's (almost transcendental) philosophy, that the human mind is tied to classical concepts, and that quantum theory can only be formulated in terms of complementary concepts of classical mechanics. And, yes, studying the foundations of quantum mechanics was a career hazard! (I'm probably not the only one who can confirm that!)

One quote was from Feynman, “Quantum physics is right!” Why are you even looking??

Feynman had also this to say (The Character of Physical Law):

I am going to tell you what nature behaves like. If you will simply admit that maybe she does behave like this, you will find her a delightful, entrancing thing. Do not keep saying to yourself, if you can possibly avoid it, 'But how can it be like that?', because you will get 'down the drain', into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.

How could this be a non-issue?

The situation has changed dramatically through the work of the brave experimentalists, who have created a new industry with quantum cryptography, quantum teleportation, and quantum computation. But we still don't really understand quantum theory. (Hopefully before the hundredth anniversary 2025.)

 

[BillTre]

 

[berkeman]

Researchers have created a device that uses machine vision to spot cockroaches and zap them with a laser.

What could possibly go wrong?

 

[Borg]

What could possibly go wrong?

I have no idea.

 

[Ibix]

What could possibly go wrong?

Cockroach insurgency stealing the tech, leading to cockroaches armed with AI driven auto-targeting anti-human lasers?

 

[fresh_42]

I have once seen ants doing that job. Very impressive.

 

[BillTre]

I have also read about similar mosquitos zappers to fight malaria:

https://en.wikipedia.org/wiki/Mosquito_laser
There is a video there which I could not copy.

 

[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.

 

[pbuk]

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.

Yes, I was thinking of the situation where there were both opening and closing [PLAIN][/PLAIN] tags (the opening tag would work but the closing tag wouldn't). @mfb provides an improvement on the colour hack, there is also [[plain]PLAIN][[/plain]/PLAIN].

 

[mfb]

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.

Sure, all but one tags need to be broken up.

 

[Orodruin]

Matlab actually has object orientation ...

 

[fresh_42]

O.k., do not travel with Tom Hanks. Obviously. But TIL that flying XY191 is dangerous, too!
https://en.wikipedia.org/wiki/Flight_191

 

[ridgerunner]

Today I learned the PF implementation of LaTex/MathJax!

Because of this cool PF feature, (i.e. pretty-printing Math formulae), I decided to go ahead and join up today, (and donate enough to become a lifetime Gold Member). Reason being; I need a place to publish my recently developed derivation of a set of force and power equations which describe the behavior of an idealized DDWFTTW cart operating at and beyond wind speed. (These derivations utilize the same assumptions, nomenclature and fundamental Newtonian Mechanics principles as those used to derive the WikiPedia Betz Law proof.)

e.g. The following equation defines the net force acting on the cart, where: $\rho$ is the fluid density in kg/m³, $S$ is the swept area of the rotor disc in m², $V_{wind}$ is the velocity of the air in the ground reference frame in m/s, $n$ is the dimensionless cart speed ($n = \frac {V_{cart}} {V_{wind}}$), and $\Delta$ is the dimensionless change in velocity of the air passing through the propeller's control volume ($\Delta = \frac {V_2 - V_1} {V_{wind}}$):
$$\left[ F_{net} = \frac 1 2 \rho S V_{wind}^2~*~ \frac 1 n \left\{-\frac 1 2 \Delta^3 + (2 - n) \Delta^2 + (2 n - 2) \Delta \right\} \right]_{\rm{14c.}}$$
Stay Tuned!
(p.s. This is my first post. In the immortal words of Dr. Nick: Hi, Everybody!

 

[berkeman]

Reason being; I need a place to publish my recently developed derivation of a set of force and power equations which describe the behavior of an idealized DDWFTTW cart operating at and beyond wind speed.

Welcome to PF. We don't allow self-publishing your work here (it needs to be published in a reputable peer-reviewed journal first), but we do have several threads about the DDWFTTW subject that you should be able to participate in. Send me a Private Message (PM) if you have trouble finding those existing threads.

 

[ridgerunner]

...
$$\left[ F_{net} = \frac 1 2 \rho S V_{wind}^2~*~ \frac 1 n \left\{-\frac 1 2 \Delta^3 + (2 - n) \Delta^2 + (2 n - 2) \Delta \right\} \right]_{\rm{14c.}}$$
Stay Tuned!
(p.s. This is my first post. In the immortal words of Dr. Nick: Hi, Everybody!

Welcome to PF. We don't allow self-publishing your work here (it needs to be published in a reputable peer-reviewed journal first), but we do have several threads about the DDWFTTW subject that you should be able to participate in. Send me a Private Message (PM) if you have trouble finding those existing threads.

Are you saying that the only equations/derivations that should be posted here are those that have been previously published in peer reviewed scientific journals? That makes no sense! When I joined up yesterday, I assumed that freely discussing physics is what this forum was all about. I was simply hoping to publish... post my derivations here, (using the clean mathematical presentation tools you provide), to elicit critical feedback from your community. I would think that you would be happy to receive and discuss new, unproven ideas in addition to known, well established science. Am I wrong?

p.s. I am aware of, (and have thoroughly read), most of the DDWFTTW related threads here on PF, (as well as many other locations across the internet), as I have been closely following this subject for more than a dozen years.

 

[hmmm27]

I think this is the most recent...

 

[PeterDonis]

I would think that you would be happy to receive and discuss new, unproven ideas in addition to known, well established science. Am I wrong?

Yes. We don't allow discussion of personal research and personal theories here because we have found, through bitter experience with trying such things in the past, that it doesn't work; nothing worthwhile ever comes out of it and it becomes a huge nightmare of threads with invalid content in them and unending arguments.

When I joined up yesterday, I assumed that freely discussing physics is what this forum was all about.

The primary purpose of PF is to help people understand physics that is already mainstream. We do have some forums, such as the QM interpretations subforum and the Beyond the Standard Model forum, where we have discussion of work that is not yet mainstream (because there are no mainstream theories or interpretations in those areas, at least not yet), but even there discussion should be based on published research, not on the personal research or theories of members.

 

[strangerep]

TIL... courtesy of Dilbert (actually, Catbert), that whisker fatigue is a real thing.