Today I Learned

[fresh_42]

TIL a nice expression in integration: "If nothing works, use the substitution of desperation, the entire denominator."

 

[fresh_42]

TIL that there is such a thing as "... standardised to the European Standard Population". Quite logical if you think about it, but I never had thought about it.

 

[CaptainAmerica17]

TIL about personal responsibility. It's not fun cramming for school projects when the end of the semester is in a month and a half. Now I'm doing stress-relief math at 2 am.

 

[Demystifier]

Today I learned that "Bohemian rhapsody" is the most performed song of the 20th century. Perhaps I should change the title of my recent paper linked in my signature and call it "Bohmian rhapsody for instrumentalists".

 

[Stavros Kiri]

TIL about personal responsibility. It's not fun cramming for school projects when the end of the semester is in a month and a half. Now I'm doing stress-relief math at 2 am.

You're the captain! ...

 

[CaptainAmerica17]

You're the captain! ...

With great power comes great responsibility!

 

[Buzz Bloom]

TIL about the following site:

http://photography.nationalgeographic.com/photography/photo-of-the-day/?​

This link will display the photo for the current day. With your cursor on the picture, the symbol ">" on the right shows you the previous day's photo. If you keep clicking on this symbol, you will see the series of photos day by day going back at least to December 2017. I do not know how far back the series goes.

Hope you find this entertaining, but beware, it can become addictive.

 

[jim hardy]

"Bohemian rhapsody"

not the "Queen" version surely..

i'd assumed it was a sibling to this one

 

[Stavros Kiri]

With great power comes great responsibility!

Keep it up! ...

 

[jtbell]

Today I learned about the airport cell phone lot.

For the first time in several years, I had to pick up a guest at the nearest airport. I figured I would do what I had done before, namely park in the garage, go into the terminal to meet him at the baggage claim, then pay a couple of dollars when leaving the garage.

Along the entrance road, I saw a sign, "Cell Phone Lot." Aha! I could park there for free, wait for my guest to text me his location at the curb in front of the terminal after he arrived and picked up his bags, and then simply zip over to the terminal. This is not a huge airport like Chicago O'Hare, so just 2-3 minutes after his text, we were on our way.

As I was leaving the cell phone lot, I noticed that most of the other cars were parked facing the opposite direction to me. Behind me (and in front of them) was an electronic flight arrival board similar to the ones inside the terminal. I hadn't noticed it when entering the lot, and I was checking the arrival status on the airport's website on my phone anyway, so I didn't really need it. It reminded me of a drive-in movie theater.

Just now I've read online that some cell phone lots also have restrooms, and even food trucks to provide refreshments.

 

[DaveC426913]

I am confused.
1] What does a cell phone have to do with the lot? I'm guessing you can wait there and have the arriver call when he's coming out?
2] What about 'cell phone lot' made you realize it would be free?

 

[jtbell]

I am confused.
1] What does a cell phone have to do with the lot? I'm guessing you can wait there and have the arriver call when he's coming out?

Exactly. And I could amuse myself by reading PF etc. on my phone while waiting.

2] What about 'cell phone lot' made you realize it would be free?

I had to drive into the entrance to investigate. It was actually "carved out" from part of a paid parking lot, using a fence. The paid part required driving through a gate; the cell phone part didn't. A sign stated that one could park in the cell phone lot for up to 30 minutes, and the vehicle must be attended at all times.

Now that I think of it, the "paid" part of the lot must be for airport workers, with the gate triggered by an ID card. It's not far from the cargo area, but kind of a long hike from the passenger terminal.

 

[Stavros Kiri]

Along the entrance road, I saw a sign, "Cell Phone Lot." Aha! I could park there for free, wait for my guest to text me his location at the curb in front of the terminal after he arrived and picked up his bags, and then simply zip over to the terminal. This is not a huge airport like Chicago O'Hare, so just 2-3 minutes after his text, we were on our way.

Who knows, may be in the future (e.g. with 5G net, coordinated autonomous vehicles and planes, intenet of things etc.) we could even have more drive-through and drive-in services and facilities at airports, such as e.g. drive though check in (and baggage check in), drive through baggage claim, drive in waiting lot and check in and ticket issue automatically via the inernet, from your car, with smartphone or computer and portable printers ...
That would save time waiting in lines, or cut down on the suggested "2 hours in advance" ...
We could even see drive-through boarding on planes (in connection to the former drive through check in and baggage ...).
All that, of course, before we are all able to have our own "flying vehicles" ...

 

[DaveC426913]

Who knows, may be in the future (e.g. with 5G net, coordinated autonomous vehicles and planes, intenet of things etc.) we could even have more drive-through and drive-in services and facilities at airports, such as e.g. drive though check in (and baggage check in), drive through baggage claim, drive in waiting lot and check in and ticket issue automatically via the inernet, from your car, with smartphone or computer and portable printers ...
That would save time waiting in lines, or cut down on the suggested "2 hours in advance" ...
We could even see drive-through boarding on planes (in connection to the former drive through check in and baggage ...).
All that, of course, before we are all able to have our own "flying vehicles" ...

I see some problems there. A lot of the red tape in airports is redundancy is passive security - such as physically clapping eyes on who is picking up the tickets, and who is dropping off luggage. Every monitored checkpoint is another place where ne'er-do-wells can get caught.

While it would be freakin' awesome to drop my luggage straight from my trunk to the conveyor, I'm not sure it's worth the security risk.

 

[Stavros Kiri]

I see some problems there. A lot of the red tape in airports is redundancy is passive security - such as physically clapping eyes on who is picking up the tickets, and who is dropping off luggage. Every monitored checkpoint is another place where ne'er-do-wells can get caught.

While it would be freakin' awesome to drop my luggage straight from my trunk to the conveyor, I'm not sure it's worth the security risk.

Security is one problem. I am sure there are others too. I was planning to mention it but at the end I forgot. However, the same issue is central with a 5G net and internet of things, which they are currently working to improve (security). The red tape for security could (potentially) get alleviated, and more advanced sensors etc. would be designed for the drive-through purposes, I guess.

 

[fresh_42]

While it would be freakin' awesome to drop my luggage straight from my trunk to the conveyor, I'm not sure it's worth the security risk.

Imagine that I had been of the firm opinion - before 9/11! - that flying takes too long, especially on shuttle routes like London - *. I seriously thought that it should become like a bus trip sooner or later. Why should it take hours to check in on a flight that lasts no longer than 3 hours? On highly frequently routes I thought: "arrival at the airport - buy the ticket - check in - board" should be a matter of ten minutes! E.g. if you have a look on the passengers on a Monday morning between London and Frankfurt, then you will see: they do not fly, they commute!

 

[Klystron]

I visited a recently remodeled store implementing customer service queues such as at a bank. Several 'tellers' in windows with waiting lines. Customers gather in an outer waiting room. Periodically, all available customers are ushered en masse to fill the queues for next_available_teller.

All well and good except each window has its own queue! (I refrained from calling "Form one line!").

Mass of customers fill open queues and wait for 'their' teller. No crossing to other lines. Has management defeated the purpose of a queue?

[Now I'm curious given N open windows how many wait queues are optimum? Also given maximum occupants in the room? Applying mental min-max tells me one per room; but I hate waiting in lines ]

 

[Drakkith]

Today I learned that the first detected black hole merger released more than 3 solar masses of energy as gravitational waves in less than a second. This was equivalent to 5.3x10⁴⁷ joules, and the peak power was greater than the power output of all stars in the visible universe combined. COMBINED.

 

[mfb]

On highly frequently routes I thought: "arrival at the airport - buy the ticket - check in - board" should be a matter of ten minutes!

Boarding alone takes longer than that unless it is a really small plane.
You can arrive at the airport an hour before your flight - if you don't have checked bags and get priority access at the security checkpoint (easy to get if you fly frequently) that is enough time. Boarding for big airplanes begins something like half an hour before the flight.

 

[fresh_42]

It took too long, it takes too long, and no betterment in sight! My dream of the layout of the boards everywhere is:
"destination - Airline - available seats - departure (- maybe costs)"
and a realistic expectation of time required: Check opportunities, go to the check in and buy the ticket (10m), go to the gate (5m, even on large air ports), boarding (5m - since there is no need to board all at once!), reserve time (10m) = 30m in total.

I know it is impossible for several reasons, but that was what I dreamt of: it should be as easy as a trip by bus or taxi. I remember once on SVO: I had to x-ray the same backpack at least four times all in all (don't remember the exact number, but it was ridiculous). Of course it was not ridiculous if you take these idiots into account, but that was part of my vision, too, that people do not murder strangers and everybody just wants to get from A to B.

 

[mfb]

boarding (5m - since there is no need to board all at once!)

If the airplane makes multiple stops on the way to your destination you lose much more time. You want a direct flight, or at least just 2-3 flights for more complicated trips.

 

[CWatters]

Today I learned on YouTube that you can kill a phone by putting it in 2% Helium Air mix. Apparently the MEMs oscillators are sensitive and stop working for several days.

 

[nitsuj]

Today I learned it's plausible to open a door, and then have one of these metal bars fall on your head. Careful out there! lol

I just went and did the math of g after a meter...it was probably traveling about 15km/h; figuring it's not much of a glider.

 

[jim hardy]

Ouch ! Sorry to hear of your mishap!

 

[Tom.G]

At least they can't lock you out (or in) now.

 

[skyshrimp]

TIL that there are as may neurons in the human intestine as there are in a cat's brain.

 

[pinball1970]

I am studying abiogenesis at the mo and I decided to find a decent biology forum. First page I went to recommended...you guessed it. Physics forums!

 

[BillTre]

I am studying abiogenesis at the mo and I decided to find a decent biology forum. First page I went to recommended...you guessed it. Physics forums!

I would agree with that.
I have checked out a few biology forums, but have not found one as nice as the Physics Forums.

Let me know if you find a good one.

 

[jtbell]

Today I learned about a new tool for dairy farmers: facial recognition for cows.

I bet it doesn't use just the faces.

 

[Stavros Kiri]

Today I learned about a new tool for dairy farmers: facial recognition for cows.

I bet it doesn't use just the faces.

While 'cow facial and waxing' I'm sure already existed ...

 

[jtbell]

My previous post was inspired by an article in this week's New Yorker magazine about facial recognition technology. It discusses the company that is applying it to cows:

[...] Cainthus's head of product science [...] grew up in Brooklyn, earned a Ph.D. in high-energy physics from Yale, and spent five years smashing subatomic particles at CERN's Large Hadron Collider, in Switzerland. She is now a student of cow behavior.

Yet another example of where you can end up with a physics Ph.D.!

 

[Stavros Kiri]

TIL that there are as may neurons in the human intestine as there are in a cat's brain.

Yup! There's a second brain down there! ...
https://www.livescience.com/62683-colon-brain-neuron-firing-pattern-detected.html

 

[skyshrimp]

You know how we're related to earthworms Stavros? The human intestine / digestive system is basically a 5 foot worm with it's organs on the outside and a calcium phosphate skeleton so it can walk.

It seems that vertebrates are evolved worms.

 

[dlgoff]

It seems that vertebrates are evolved worms.

References please.

 

[skyshrimp]

Look in the belly.

 

[fresh_42]

It seems that vertebrates are evolved worms.

Fishes, not worms.

 

[StevieTNZ]

Today I learned that Professor Roy Glauber died.

 

[mfb]

Look in the belly.

I didn't find any publications there.
"Worm" is a poorly defined group, but vertebrates (part of Chordata) don't come from any group of worms.

 

[BillTre]

"Worm" is a poorly defined group

Yes. In addition, the word "worm" can be used in different ways in biology:

1) general outside shape; like a worm (long and skinny, often wiggly or squirmy), ends could be pointy or rounded; vermiform

2) Organisms that are phylogenetically related to present day worms (see @mfb's post above), not in any obvious way.

3) a general worm-like body plan (this is what @skyshrimp may have been talking about.
However, he seems to equating just the inner (gut) tube as the worm.
Perhaps he meant just a single tube, thereby ignoring other wonderful aspects of worminess.

Topologically, most body plans of animals can be reduced or simplified by pushing in the limbs to make a flatter surface without changing its planar contintuity (there's probably a name for this).
Doing this reduces them to either a sphere or a donut or torus shape (often described as a tube within a tube).
An elongated donut would be pulled into a tube within a tube shape, where the outside layer is the ectoderm (protective skin surface).
The inside layer is the endoderm which forms the gut (all the internal digestive surfaces of the body).
The sheet of gut cells is continuous with the outer surface curved into the middle of the donut).
See figure 4 https://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookDiversity_7.html. This is a traditional conceptual diagram of the main features of body plans of three different phyla (all worms) with a tube within a tube tissue organization.
Similarly, a sphere shape cold have a pushed in surface to make it cup shaped. The possibly protected, pushed in surface cold be specialized in digestion of food and absorption of nutrients. This would form a bag within a bag topology and a one ended gut.

Upon developing directional movement, and organism would be expected to acquire front and back end specializations for sensory and motor control as well as in what goes on at the front end of the digestive tube as opposed to the back end.
Efficiency would drive these features which are widely found in different animals.
At some point a two ended gut could be formed by either:

• A part of the folded in surface of could instead fuse with a different area of the outside of the sphere that it is pressed up to on their inside surfaces.

or:

• the sides of the elongated pinched in surface would fuse together (at the tissue level (sheets of cells)) to form a tunnel for food input at one end and waste offloading at the other. (I like this one better because the change expected would be less of a big modification in how things were operating than creating a new opening (with new flows of materials) would require.)

It has therefore been assumed that the simplest of early metazoans in the animal lineage would have evolved the first of body plans through a sequential addition of features such as:

• have tissues specially organized cells, cell types
  
• inside/outside (like ectoderm/endoderm) distinction
  
• top/bottom axis and later an axial position readout system
• Front/back axis and later an axial position readout system
• Ball to Donut shape transformation (formation of a tubular gut from a pinched in region); therefor distinguish endoderm/ectoderm molecularly (This would be a the worm-like body plan

Although these kinds of transformations may not be allowed in topology (so I have heard!), it is not that difficult for biological systems to create new openings or fuse an opening closed during embryology.

4) The simplest of bilateral organisms would have the head/tail, top/bottom, inside/outside distinctions. Soon after a tubular worm-like (tube within a tube) body plan would be evolved. This according to @mbf's link, would be at the level the xenacoelomorpha group branches off. The last common ancestor of both the protostomes and the deuterostomes.
Xenacoelomorphs are very primitive. They have a front/back, top/bottom, a primitive digestive system with only one opening (mouth/anus), a kind of bag inside a bag body plan that can be simplified to a sphere.
They have not yet formed the tube within a tube aspect of their body plan.
Some might call them a worm. They are shaped somewhat like a flatworm, which also have single ended guts.

Immediately after this branch point in the phylogeny shows the split between the protostomes and the deuterostomes, which is a distinction based upon which end (the mouth or the anus) forms first in development (the cellular processes that shape and determine the adult body form).
This basic feature of the body plan, may have been set-up independently, which could explain the difference,
or there might have been some kind of anatomical transformation of the mouth or anus location.

 

[OmCheeto]

Today I learned that there is a fish that is afraid of the water.

Blue Planet II: Meet the fish which is so scared of water it lives in a cave

It is not easy being a fish when you are afraid of the water.

So spare a thought for the leaping blenny, which detests the sea so much, it chooses to live in miniature cave three feet above the tide-line in Guam, Micronesia, and scampers to higher ground when it notices even the smallest wave approaching.

The Pacific leaping blenny, which needs to frequently roll around in coastal puddles to stay wet, has been filmed for the first time by BBC’s Blue Planet II.​

 

[jim hardy]

So spare a thought for the leaping blenny, which detests the sea so much, it chooses to live in miniature cave three feet above the tide-line in Guam, Micronesia, and scampers to higher ground when it notices even the smallest wave approaching.

Wow - and i thought I was neurotic !

 

[Klystron]

Today I learned that Cantor set theory is still controversial at least among those who /can/ do not understand it.

 

[mfb]

Give the fish a few million years more (and no human influence) and it becomes more adapted to life on land.
Wouldn't be the first time...

 

[DaveC426913]

Give the fish a few million years more (and no human influence) and it becomes more adapted to life on land.
Wouldn't be the first time...

Or the second...

https://www.telegraph.co.uk/science/2017/12/01/meet-fish-scared-water-lives-cave/
“One marine creature has virtually abandoned the sea altogether. On a few remote Pacific islands lives the most terrestrial fish on the planet. These Pacific Leaping Blenny seem afraid of the waves."

 

[fresh_42]

TIL where the word ghetto comes from.

It originated from Venetian Italian. The copper manufacturers lived in a certain part of town and used to throw their waste all on the same place. To throw away meant gettare in the local dialect and the place became getto. When the jews were forced to move in this part of town, they pronounced it ghetto, according to the German pronunciation of Yiddish.

 

[mfb]

Today I learned about a curious nearly-pattern in the decimal system:

$10^{14}-1 = 909,091 \times 109, 999,989$
$10^{24}-1 = 99,990,001 \times 9,901 \times 1, 010,099, 989,899$
$10^{36}-1 = 999,999, 000,001 \times 9,901 \times 100, 999,999, 999,999, 999,899$
$10^{38}-1 = 909,090,909,090,909,091 \times 109, 999,999, 999,999, 999,989$
$10^{39}-1 = 900,900,900,900,990,990,990,991 \times 1,109, 999,999 ,999,889$
$10^{48}-1 = 9,999, 999,900, 000,001 \times 99, 990,001 \times 1, 000,100, 009,999, 999,899 ,989,999$
$10^{62}-1 = 909,090,909,090,909,090,909,090,909,091 \times 109 ,999,999 ,999,999 ,999,999 ,999,999, 999,989$
$10^{72}-1 = 999999 000001 \times 99 990001 \times 9901 \times 101 \times 10,000, 999,999 ,989,998, 989,999 ,010,001, 010,000, 999,999 ,989,999$
$10^{78}-1 = 900,900, 900,900, 990,990, 990,991 \times 1 ,109,999, 999,999, 889,000, 000,000, 000,000 ,000,000 ,001,109, 999,999 ,999,889$

The numbers get too large for an exhaustive search, but two larger examples:
$10^{93}-1 = 900,900,900,900,900,900,900,900,900,900,990,990,990,990,990,990,990,990,990,991 \times 1,109,999,999,999,999,999,999,999,999,999,889$
$10^{196}-1 = 999,999,999,999,990,000,000,000,000,099,999,999,999,999,000,000,000,000,009,999,999,999,999,900,000,000,000,001 \times 900,900,900,900,990,990,990,991 \times 11,099, 999,999 ,999,000 ,999,999 ,999,988, 900,000, 000,011 ,099,999, 999,999, 000,999, 999,999 ,988,900 ,000,000, 011,099 ,999,999$

In each case all factors apart from the last one are prime numbers.

 

[Stavros Kiri]

Today I learned about a curious nearly-pattern in the decimal system:

$10^{14}-1 = 909,091 \times 109, 999,989$
$10^{24}-1 = 99,990,001 \times 9,901 \times 1, 010,099, 989,899$
$10^{36}-1 = 999,999, 000,001 \times 9,901 \times 100, 999,999, 999,999, 999,899$
$10^{38}-1 = 909,090,909,090,909,091 \times 109, 999,999, 999,999, 999,989$
$10^{39}-1 = 900,900,900,900,990,990,990,991 \times 1,109, 999,999 ,999,889$
$10^{48}-1 = 9,999, 999,900, 000,001 \times 99, 990,001 \times 1, 000,100, 009,999, 999,899 ,989,999$
$10^{62}-1 = 909,090,909,090,909,090,909,090,909,091 \times 109 ,999,999 ,999,999 ,999,999 ,999,999, 999,989$
$10^{72}-1 = 999999 000001 \times 99 990001 \times 9901 \times 101 \times 10,000, 999,999 ,989,998, 989,999 ,010,001, 010,000, 999,999 ,989,999$
$10^{78}-1 = 900,900, 900,900, 990,990, 990,991 \times 1 ,109,999, 999,999, 889,000, 000,000, 000,000 ,000,000 ,001,109, 999,999 ,999,889$

The numbers get too large for an exhaustive search, but two larger examples:
$10^{93}-1 = 900,900,900,900,900,900,900,900,900,900,990,990,990,990,990,990,990,990,990,991 \times 1,109,999,999,999,999,999,999,999,999,999,889$
$10^{196}-1 = 999,999,999,999,990,000,000,000,000,099,999,999,999,999,000,000,000,000,009,999,999,999,999,900,000,000,000,001 \times 900,900,900,900,990,990,990,991 \times 11,099, 999,999 ,999,000 ,999,999 ,999,988, 900,000, 000,011 ,099,999, 999,999, 000,999, 999,999 ,988,900 ,000,000, 011,099 ,999,999$

In each case all factors apart from the last one are prime numbers.

Is this for real?
[And I was wondering why my knowledge was incomplete! Seems I found what was missing! ... ]

 

[mfb]

You can check them with WolframAlpha or Dario Alpern's tool (which I used for factorization).
I got the idea from unique primes: If a prime is a unique prime with a period length p, then it is the largest factor of 10^p-1.

 

[Stavros Kiri]

You can check them with WolframAlpha or Dario Alpern's tool (which I used for factorization).
I got the idea from unique primes: If a prime is a unique prime with a period length p, then it is the largest factor of 10^p-1.

Thanks for the tips.

I got the idea from unique primes: If a prime is a unique prime with a period length p, then it is the largest factor of 10^p-1.

I am beginning to see the mechanism now

 

[nitsuj]

TIL that Canada has a "digitize stuff*" website, and recently just added a ton of stuff.

The site is called Canadiana and is "run" by CRKN - "The Canadian Research Knowledge Network is a partnership of Canadian universities, dedicated to expanding digital content for the academic research and teaching enterprise in Canada."