Today I Learned

[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 [COLOR=rgb(0,0,0)][[/COLOR] hack any more?

 

[fresh_42]

Ooo, when was that introduced? You mean we don't have to use the [COLOR=rgb(0,0,0)][[/COLOR] 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##.

 

[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}[i]## (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 [PLAIN][/PLAIN] you still need to use the color hack: [COLOR=rgb(0,0,0)][[/COLOR]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]
  
  [COLOR=rgb(0,0,0)]#[/COLOR]#[COLOR=rgb(0,0,0)][[/COLOR]PLAIN] \mathbb{C}\cong \mathbb{R}[i] [COLOR=rgb(0,0,0)][[/COLOR]/PLAIN] [COLOR=rgb(0,0,0)]#[/COLOR]#

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: ##a[ i]## -> $a[ i]$

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

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

0
One color tag is enough to break up MathJax tags: #[color=black]#[/color]a^3## -> ##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 [COLOR=rgb(0,0,0)][[/COLOR] 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.

 

[Rive]

whisker fatigue is a real thing.

Well. Should we redefine 'tickling' as 'skin fatigue', then?

 

[anorlunda]

LOL Old school triumphed today.

I've been having trouble with the AC in my RV. I called for a repairman and told him that I thought a relay contact was stuck closed.

The guy came, and started running tests and making measurements. He just graduated from AC technician school this year. He was surprised that the AC is 21 years old. He said new ones only last 5-6 years. When he got into the control board, there sat a big black relay. He was thinking of replacing the relay or finding a replacment board. My wife said, "Hell, just whack it." The repairman looked stunned. But we convinced him. He whacked it with a rubber mallet and now everything works fine again. I spent $50 on his call instead of $1000 for a new AC of inferior quality.

He shook his head and said, "My buddies won't believe me when I tell them I fixed it with a mallet."

You see my wife remembers our first car. It had a sticky relay in the voltage regulator. She knew that when the voltage went high, that she should fetch the tire iron and give the regulator a firm whack. That worked for the lifetime of that car.

Old school. It worked then, and it can still work today in the right circumstances.

 

[Tom.G]

I spent $50 on his call...

...because I didn't ask my wife first!
(been there... )

 

[pinball1970]

LOL Old school triumphed today.

I've been having trouble with the AC in my RV. I called for a repairman and told him that I thought a relay contact was stuck closed.

The guy came, and started running tests and making measurements. He just graduated from AC technician school this year. He was surprised that the AC is 21 years old. He said new ones only last 5-6 years. When he got into the control board, there sat a big black relay. He was thinking of replacing the relay or finding a replacment board. My wife said, "Hell, just whack it." The repairman looked stunned. But we convinced him. He whacked it with a rubber mallet and now everything works fine again. I spent $50 on his call instead of $1000 for a new AC of inferior quality.

He shook his head and said, "My buddies won't believe me when I tell them I fixed it with a mallet."

View attachment 316904

You see my wife remembers our first car. It had a sticky relay in the voltage regulator. She knew that when the voltage went high, that she should fetch the tire iron and give the regulator a firm whack. That worked for the lifetime of that car.

Old school. It worked then, and it can still work today in the right circumstances.

Reminded of….

 

[Rive]

My wife said, "Hell, just whack it."

I guess that may hint some ... 'consultation fee' ... especially in account of that $950 saved

 

[anorlunda]

By the way, I owe my career to a faulty relay .

The Great Northeast Blackout of November 9, 1965 launched my career as a power engineer. The investigation showed that the triggering event was caused by a moth in a relay at the Sir Adam Beck power plant in Ontario.

 

[jack action]

By the way, I owe my career to a faulty relay .

The Great Northeast Blackout of November 9, 1965 launched my career as a power engineer. The investigation showed that the triggering event was caused by a moth in a relay at the Sir Adam Beck power plant in Ontario.
View attachment 316926

Haaa! the famous "bug":

The term "bug" was used in an account by computer pioneer Grace Hopper, who publicized the cause of a malfunction in an early electromechanical computer. A typical version of the story is:

In 1946, when Hopper was released from active duty, she joined the Harvard Faculty at the Computation Laboratory where she continued her work on the Mark II and Mark III. Operators traced an error in the Mark II to a moth trapped in a relay, coining the term bug. This bug was carefully removed and taped to the log book. Stemming from the first bug, today we call errors or glitches in a program a bug.

 

[anorlunda]

Haaa! the famous "bug":

Her's was the first of a long line of notable bugs.

 

[BillTre]

 

[anorlunda]

5200 Drone light show, Breaking 4 World Records -- High Great​

What fun it would be to write the software.