Today I Learned

[hagopbul]

today i learned not to visit a university library after you finish your courses in that university

 

[berkeman]

today i learned not to visit a university library after you finish your courses in that university

How come? Brings back too many memories? They won't let you in without an active student badge? You still have overdue books checked out?

 

[symbolipoint]

today i learned not to visit a university library after you finish your courses in that university

Unimaginable! Many years ago, I learned the opposite.

 

[strangerep]

today i learned not to visit a university library after you finish your courses in that university

Unimaginable! Many years ago, I learned the opposite.

#MeToo.

 

[DaveC426913]

today i learned not to visit a university library after you finish your courses in that university

Having not gone to university, the lesson here entirely escapes me.

 

[Klystron]

My favorite study area was a carrel up on the library reference floors, quiet with little traffic. Only needed to show student ID card to borrow books and use computers IIRC. The university installed RFID on materials and alarms at exits to reduce theft; now common security devices at most libraries.

 

[BillTre]

Here is a NY Times article by Randle Munroe (XKCD) about what the worst smell is.
Not a lot of science, but interesting stories and a de-scent into humor.

 

[strangerep]

My favorite study area was a carrel ...

Today I learned that those quiet little cubicles in the old Physics library, and in Fisher Library stack, where I used to love spending endless amounts of time, had a specific name.

They infuse a feeling hard to describe... and often there's lots of other intellectually oriented people nearby, mostly head-down tail-up,...

 

[Adesh]

Today I learned that Cliff Booth (I’m talking about the movie Once Upon A Time in Hollywood) was a fictional character.
Actually, yesterday I saw the movie and really admired Cliff Booth (Brad Pitt) too much, he seemed to me a man who doesn’t care about life anymore all he wanted a square meal and almost no recognition. But today...

 

[epenguin]

Today I learned that those quiet little cubicles in the old Physics library, and in Fisher Library stack, where I used to love spending endless amounts of time, had a specific name.

They infuse a feeling hard to describe... and often there's lots of other intellectually oriented people nearby, mostly head-down tail-up,...

Naughty, subversive, anti-intellectual but great poetry with the memorable line

"Hanging like bats in a world of inverted values"

https://books.google.co.uk/books?id=m2m_tGGUi5IC&pg=PT140&lpg=PT140&dq=hanging+like+bats+world+of+inverted+values&source=bl&ots=bBcblC03M1&sig=ACfU3U3liDp93CwsWzuydu8nAoelm8r87A&hl=en&sa=X&ved=2ahUKEwiz7vvBt93nAhU1t3EKHfAFA3IQ6AEwDHoECAsQAQ#v=onepage&q=hanging like bats world of inverted values&f=false

But Hey!
https://www.physicsforums.com/threa...-joy-of-reading-15-7-22-7.761845/post-4801572

There went I!

(Not the BL but almost as venerable.)

 

[pbuk]

...that it was called "Gateway to the South"...

I thought that was Balham?

 

[epenguin]

I thought that was Balham?

I abstained from saying so as I thought few people here would get it.

 

[hagopbul]

How come? Brings back too many memories? They won't let you in without an active student badge? You still have overdue books checked out?

yes they didnt

 

[hagopbul]

today i learned helping is good in general

 

[Adesh]

Today I learned about John Michell.

Have you ever heard of this scientist earlier? Probably not !
John Michell (25 December 1724 - 21 April 1793) was English natural philosopher and clergyman who provided pioneering insights in a wide range of scientific fields, including astronomy, Geology, Optics and gravitation. Considered 'one of the greatest unsung scientists of all time'. The American Physical Society (APS) has described Michell as being "so far ahead of his scientific contemporaries that his ideas languished in obscurity until they were re-invented more than a century later". The APS states that while "he was one of the most brilliant and original scientists of his time, Michell remains virtually unknown today".
Newton in 1665 discovered that everything possesses gravity, it is the force by which a body pulls everything inwards, towards itself. Michell combined the notion of gravity that it pulls everything inwards by Newton and the notion of speed of light being finite by Ole Rømer, he said that if a star has mass which is a lot, lot more than the sun then the light which it is emitting would be pulled in on itself because of gravity, he concluded that maybe the most massive objects of this universe are invisible and this formed the base of modern-day black hole theories. He is the father of seismology and father of Magnetometry. He was the first to explain how to manufacture artificial magnets. He applied statistics to study cosmos, he told double stars were a product of mutual gravity. He also invented a apparatus to measure the mass of Earth. Imagine what if this great scientist never existed, would have we known these secrets of our cosmos. He is an unsung great scientist, today his contributions in astronomy, Geology, Optics, and gravitation form the base of modern-science, yet we don't know about this famous scientists.

A grand salute to you Mr. John Michell.

 

[DaveC426913]

Turns out Mr. Michell is a trickster, and the truth is much more mundane. Mr. John Michell didn't discover any of those things. All he did was invent the world's only time machine.

 

[Adesh]

Turns out Mr. Michell is a trickster, and the truth is much more mundane. Mr. John Michell didn't discover any of those things. All he did was invent the world's only time machine.

Time machine?

 

[DaveC426913]

Time machine?

A joke.
He went into the future and stole all those ideas.
The irony, of course, being that inventing a time machine would be way a more impressive feat - not mundane at all.

 

[Adesh]

A joke.
He went into the future and stole all those ideas.
The irony, of course, being that inventing a time machine would be way a more impressive feat - not mundane at all.

It was a very very complicated joke, Ah! But after all joke is a joke :)

 

[mfb]

A true trickster would never invent the time machine. They would steal it from the person who did.

Imagine what if this great scientist never existed, would have we known these secrets of our cosmos.

Yes, just a bit later.

 

[hagopbul]

Today I learned not to buy too much lahmaju

 

[DrGreg]

Today I learned that there is a brand of crisps in the UK called "Hint of Salt". (Translation: UK crisps = US potato chips.) With a name like that, you'd expect its salt content to be a fraction of that of standard crisps. Well, it is a fraction, but the fraction is $\tfrac{3}{4}$. Since when was $\frac{3}{4}$ a "hint"?

 

[DaveC426913]

Since when was $\frac{3}{4}$ a "hint"?

When "full-on" is "but a dash"...

 

[Merlin3189]

Today I learned two things in one post.
I can just paste an illustration into my post! For years I've always saved a file on my pc, uploaded it and inserted it. I thought I was copying text, but it was a picture of text.

I looked up how to show a vector in Latex. I'd never done it before and only wanted it now, to explain to someone that they didn't need to use vectors for their problem!

I think both will be useful in future, but both got removed from that post during editing!

 

[hagopbul]

spending the week end in bed is a good thing some time

 

[Adesh]

spending the week end in bed is a good thing some time

You have broken the rule . We are told to start with "Today I learned..."

 

[mfb]

Today I learned that Adesh broke the (self-invented?) rule, too.

 

[Ibix]

(self-invented?)

Blithely ignoring the rule while citing it, it's in post #1.

 

[Adesh]

Today I learned from @mfb and @Ibix that I shouldn’t fill this thread by my poor jokes (it’s a rule of this thread)
I don’t know if I have broken the rule again

 

[Jonathan Scott]

Today I learned that moths (or rather their larvae) have eaten away the edges of our ancient lounge carpet behind and underneath our furniture. When we had our old sofas removed today in preparation for having new ones delivered tomorrow, we found there were lots of holes and bare patches in the carpet and there were lots of empty white things about the size of a grain of rice which are apparently the case in which the larva grows. Here in the UK the culprits are apparently probably clothes moths rather than carpet moths, but they are similar.

We have often moved the sofas enough to vacuum up the dust and spiders webs which tend to form behind them, without looking too carefully down the back, but I suspect that by the law of unintended consequences the removal of the webs meant that fewer moths were caught so that probably helped them to multiply! However, I couldn't find any live moths or larvae around so perhaps they have taken a long time to get that far.

We were already provisionally planning to get new carpets anyway, but we are going to speed that up provided that we can be reassured that we can either eliminate enough of the moths or find a suitable carpet that the moths don't like to eat. (We already have one artificial fibre carpet, but the colour seems to wear off in places where it gets more use, so I'm not keen on getting another one like it).

 

[member 656954]

Today I actually looked at the PF icon and realized it's intention! Yes, I'm that slow

 

[Tom.G]

provided that we can be reassured that we can either eliminate enough of the moths

Many many todays ago I learned that Boric Acid (H₃BO₃) powder is extraordinarily effective against insects... it even kills off cockroaches! It's also less harsh to us Humans than the manufactured insecticides.

Some people here in the US have found it to work when sprinkled around before laying down carpet. Myself, I would also put a dusting on the carpet.

 

[BillTre]

External boric acid kills insects by abrading holes in their cuticle (largely chitin). The insect cuticle is water repellent and keeps the insect from drying out. Boric acid abrasions cause the insect to lose water and die.
The boric acid must be dry for this to work. Its small separate particles cause the abrasion.

We used it in fish facilties (which are a great environment for roaches) by putting it behind the drywall where the roaches often hid and nested.

 

[Tom.G]

External boric acid kills insects by abrading holes in their cuticle

That's the effect of Diatomaceous Earth (although I've found it not very effective for many bugs), could be a secondary effect of Boric Acid too. The reports I've been able to find on .GOV sites state the main route is when the cockroaches groom they eat the Boric Acid, which is poisonous. I proved the 'poisonous' once when I got some on a skinned knuckle and ignored it. My whole hand swelled up... so keep it out of open sores and don't eat it! Minor inhalation while applying hasn't caused me any noticeable effects, but I don't get careless about ventilation either.

Old-time fun fact(s): Boric Acid solution used to be used as an eye wash. Quite effective against some conditions. Don't know the concentration though. It's also effective in shoes as a deodorant and in gloves as a fungus killer.

 

[Klystron]

Boric acid dry powder is/was very effective against cockroaches infesting damp areas in otherwise dry desert xeriscape. Oddly, it became difficult to buy at nurseries that used to sell it by weight. Nursery management offered vague reasons implying that insecticide distributors or then-new Homeland Security (?) objected to this simple treatment.

Anecdotally, I have been told Borax dry hand soap works against roaches but is more expensive and less effective than the basic powder. Curious.

 

[symbolipoint]

Old-time fun fact(s): Boric Acid solution used to be used as an eye wash. Quite effective against some conditions. Don't know the concentration though.

From memory hearing an informal discussion, the solution was called "isotonic" in the characterization of the concentration.

 

[Tom.G]

From memory hearing an informal discussion, the solution was called "isotonic" in the characterization of the concentration.

That sounds vaguely familiar, which made me look it up... And to the rescue:
https://www.khanacademy.org/science/biology/membranes-and-transport/diffusion-and-osmosis/a/osmosis
In this case, meaning a solution that has the same osmotic pressure of solute as the solution within a cell does. Don't think I want to go down that rabbit hole, leave it to the chemists.

I have been told Borax dry hand soap works against roaches but is more expensive and less effective than the basic powder.

Different chemical. That stuff is Sodium Borate Decahydrate, a water softener as I recall.
(B₄Na₂O₇ · 10H₂O)

it became difficult to buy at nurseries that used to sell it by weight.

Yeah, I remember that. It is currently available in the nationwide Home Improvement hardware stores, displayed with the other insecticides. Sold in 1-pound squeeze-bottles for a few dollars.

 

[mfb]

Today I learned that $\frac{\sqrt{x^2+1}-1}{x} = \frac{x}{\sqrt{x^2+1}+1}$. Looks funny, but it works.

Spoiler

Found when reducing rounding errors for small x.
Context

 

[strangerep]

Today I actually looked at the PF icon and realized it's intention! Yes, I'm that slow

Today I read your post and realized I'd never even thought about PF icon. I've been a PF member a lot longer than you, so how slow does that make me?

 

[fresh_42]

Today I actually looked at the PF icon and realized it's intention! Yes, I'm that slow

Today I read your post and realized I'd never even thought about PF icon. I've been a PF member a lot longer than you, so how slow does that make me?

... and I still don't see what you mean. Could you enlighten me?

 

[Ibix]

... and I still don't see what you mean. Could you enlighten me?

It's a sort of atom-y thing inside a speech bubble - so "talking science" or "talking about science".

 

[fresh_42]

It's a sort of atom-y thing inside a speech bubble - so "talking science" or "talking about science".

Oh, that easy. I was looking for some message behind atoms with three valence electrons, or Lithium.

 

[strangerep]

I was looking for some message behind atoms with three valence electrons, or Lithium.

It's a good thing it wasn't a subtle message involving Uranium.

 

[fresh_42]

It's a good thing it wasn't a subtle message involving Uranium.

By the way: What do we have about the Lithium puzzle? Do we have an insight?

 

[Adesh]

By the way: What do we have about the Lithium puzzle? Do we have an insight?

But that's the classical model. Is our PF a classical forum?

 

[jbriggs444]

Today I learned that $\frac{\sqrt{x^2+1}-1}{x} = \frac{x}{\sqrt{x^2+1}+1}$. Looks funny, but it works.

Spoiler

Found when reducing rounding errors for small x.
Context

Back in high school while coding up a lunar landing game, I first encountered that issue and learned of the alternate quadratic formula: $$x=\frac{2c}{-b \pm \sqrt{b^2-4ac}}$$ which can evade the cancellation of near equal quantities and associated loss of precision.

 

[Jonathan Scott]

Today I learned that new sofas come with a chemical smell that irritates my nose and throat, and my wife hates the smell too. We left the windows open for hours (it was quite windy but only just above freezing outside) but it doesn't seem to have helped very much. I find it hard to believe that customers are really expected to put up with such an unpleasant experience, and I wouldn't be surprised if it is actually harmful to health.
I'm sure our previous ones weren't anything like so bad. Perhaps it's something to do with the"fire resistant" foam and materials, which were much less extreme 15 years ago. (No-one I know is a smoker so I can't see any benefit at all in fire resistance now). Our previous sofa had washable covers and cushions, but our new one cannot be cleaned properly at all (neither washed nor dry cleaned) because of some fireproofing treatment.
We deliberately avoided buying the "stain-proofing" treatment and insurance, mainly because of the ridiculous price (which made a mockery of the sale price of the sofa itself), but I guess that might well have made an even worse smell.

 

[fresh_42]

You should have bought a couch instead of a smell on fibers attached.

Maybe someone thought people would expect this, as they do in new cars. Btw. new airplanes have this smell of new like cars, too.

 

[strangerep]

By the way: What do we have about the Lithium puzzle? Do we have an insight?

Huh??

 

[fresh_42]

Huh??

I'm not totally sure, but isn't there a massive lack of Lithium in the universe?