Learn One Thing A Day

Free textbooks and other open educational resources

2023-10-13T08:45:00.008-07:00

Some useful resources:

It hosts the Open Textbook Library, https://open.umn.edu/opentextbooks, which currently offers more than 1200 open textbooks.

The multi-institutional LibreTexts project produces open textbooks, including in physics, https://phys.libretexts.org.

MIT offers lectures and course materials for thousands of its undergraduate and graduate classes at OpenCourseWare, https://ocw.mit.edu.

Found on https://pubs.aip.org/physicstoday/article/76/7/18/2899794/Free-textbooks-and-other-open-educational

What is the first sign of civilization?

2022-10-20T01:10:00.002-07:00

Hello Internet, today I read something definitely worth sharing.

What does make a Civilization a Civilization ?

From Quora

"Years ago, anthropologist Margaret Mead was asked by a student what she considered to be the first sign of civilization in a culture. The student expected Mead to talk about fishhooks or clay pots or grinding stones.

But no. Mead said that the first sign of civilization in an ancient culture was a femur (thighbone) that had been broken and then healed. Mead explained that in the animal kingdom, if you break your leg, you die. You cannot run from danger, get to the river for a drink or hunt for food. You are meat for prowling beasts. No animal survives a broken leg long enough for the bone to heal.

A broken femur that has healed is evidence that someone has taken time to stay with the one who fell, has bound up the wound, has carried the person to safety and has tended the person through recovery. Helping someone else through difficulty is where civilization starts, Mead said.

We are at our best when we serve others."

Meet the Library of Babel

2022-06-10T10:03:00.000-07:00

Meet the Libray of Babel , where every possible combinations of letters and words you can invent is already there.

Try it!

https://libraryofbabel.info/search.html

More info here:

The Monty Hall Problem: stick or switch?

2020-08-02T06:49:00.001-07:00

The Monty Hall Problem is nice brain teaser, based on the American television game show Let's Make a Deal and named after its original host, Monty Hall.

It became famous as a question from a reader's letter quoted in Marilyn vos Savant's "Ask Marilyn" column in Parade magazine in 1990 (Internet Archive [1])

Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3,

which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice?

The answer is YOU SHOULD ALWAYS SWITCH!

Crazy eh? Not really if you think about it in basic simple probabilistic terms.

Let's try.

At the beginning of the Game, each door is equally probable to hide the car, so 1/3.

We really cannot do much about it, we don't know neither can't do any better.

The player picks a door (let's say door 1) and has 1/3 probability to win and 2/3 to lose (there are still two doors, each one with 1/3 probability to hide the car).

In other terms, the player is likely to loose (1/3 Vs. 2/3).

(Source: Wikipedia)

Now, when the host opens one (door 3 in the picture) of the two remaining doors (which combined probability to hide the prize was and is still 2/3!!!!), we have more information!!!

Of the original 2/3 combined probability of door 2 and door 3 we now know that actually door 3 hid a goat, this means that its probability to hide the car is well.... 0, just zero!

As a consequence, door 2 gets the FULL 2/3 probability that we originally assigned to door 2 and door 3....

(source: Wikipedia)

Now, if you decide to switch and go for door 2, you have 2/3 probability to win!!!!

Still unconvinced?

Well, just scale the same problem/game up to one having 100 doors.

At the beginning you choose a door out of 100, so you have 1/100 probability to win or 99/100 to loose.

When the host asks you, will you switch? Probably yes!

After the host opens 98 doors, your original choice has still 1/100 chance to win, but the one door that the host did not open has now 99/100 chance to contain the prize!

If you switch you are very likely gonna win!!!! After all 99/100 is much bigger than 1/100, 99-bigger ;)

The problem is quite famous because the original answer by Marilyn vos Savant caused a lot of debate, the Vox video [3] makes a nice job in summarizing the controversies.

What really stuck me, is the fact that Marilyn vos Savant received many many angry letters (thousands of them!!!) by academics who refused to accept her solution (see [1][2][3])!!!

Can you believe this????

I highly recommend you to read the Wikipedia Page about the Monty Hall Problem [2] :)

A nice summary

Another nice summary

With Conditional Probability

Bonus

References to the Monty Hall Problem can be found in:

Sources

Top 10 Facts - Animals

2020-03-28T07:28:00.000-07:00

The Mathematics of Epidemics

2020-03-22T07:08:00.000-07:00

In the time of the Coronavirus COVID19, it is useful to have a look at the mathematics of epidemics.

On a sad note, Bill Gates got it definitely right.... 5 years ago!

The Trouble with Tumbles

2020-03-01T23:08:00.003-08:00

I didn't know tumbleweed was such a huge problem!

Another very interesting video by CGP Grey!

7 Driving Habits That Ruin Your Car and Drain Your Wallet

2020-02-22T02:40:00.000-08:00

True (disturbing) Facts About The Duck

2020-02-19T07:00:00.000-08:00

These are some interesting and sometimes distuburbing facts about Ducks....

How to Solve a Rubik's Cube, it works ;)

2020-02-11T07:00:00.000-08:00

I tried and it works!
It take just some practice and mnemonics:)

Some extra info:

https://ruwix.com/the-rubiks-cube/how-to-solve-the-rubiks-cube-beginners-method/

And for the lazy ones...

https://ruwix.com/online-rubiks-cube-solver-program/

17 Wrong Habits We Get from Childhood

2020-02-08T03:00:00.000-08:00

Interesting tips!
I have to change my coffee-routine too!

Your New Year's Resolution Has Already Failed

2020-02-08T02:46:00.000-08:00

This is a pretty interesting strategy.
If we try to be too hard on ourselves, we are going to fail.
I like the idea to have a theme :)

You Won't Believe How the First Spy Satellites Worked

2020-01-30T12:00:00.000-08:00

There was a time, when dedication and patience (a lot of it!) could overcome immature/pioneering technologies. And prevent wars too!
Somehow difficult to understand today.

How Monument Valley became a symbol of the West

2020-01-27T00:00:00.000-08:00

I have always wondered it :)

The Real Butterfly Effect

2020-01-24T00:59:00.003-08:00

Another wildly intersting video from Sabine Hossenfelder :)

The real reason Boeing's new plane crashed twice

2019-06-15T12:15:00.000-07:00

I asked myself the same question...

How Earth Moves

2019-06-12T05:03:00.001-07:00

Fascinating, simply fascinating :)

Why Are 96,000,000 Black Balls on This Reservoir?

2019-06-09T12:09:00.000-07:00

This is cool!

Why All Images of Space Are Photoshopped ?

2019-06-08T12:05:00.004-07:00

An interesting Video from Cheddar :)
Enjoy!

Why the Victorian mansion is a horror icon

2018-11-23T06:16:00.001-08:00

Do you remember The Addams Family? And their House?

If so, you will find this little fun fact quite interesting :)

Enjoy!

The Death of Facebook | How Social Media Ripped Apart a Generation

2018-11-17T09:08:00.000-08:00

The lack of empathy is a scary phenomenon

But I am still not sure that the demise of Facebook is really close.

The Overton Widow

2018-01-01T02:17:00.000-08:00

Happy New Year!

Usually I don't discuss polics here, but The Overton Widow is a pretty interesting psychological mechanism!

In the last 12 months, we did really get used to all the absurdities of the crazy old man -- and his team! -- that happens to rule the USA.

Why knights fought snails in medieval art?

2017-05-07T00:18:00.001-07:00

An interesting story I listed today. Worth to share it ;)

Enjoy!

Nasa's Million Dollar Space Pen vs The Soviet Pencils

2017-03-30T10:35:00.001-07:00

This is a quite interesting story... the facts behind the myth :)
Enjoy!

Where do the Bluetooth symbol and name come from?

2017-03-12T10:31:00.001-07:00

The name "Bluetooth" comes from the Scandinavian Blåtand/Blåtann and Harald "Blåtand" Gormsson (935-985) was King of Denmark and Norway.

He united dissonant Danish tribes into a single kingdom and, according to legend, introduced Christianity as well. When the name was proposed
in 1997, the implication was that Bluetooth does the same with communication devices, uniting them into one single "rule".

About the symbol itself it comes from the name of the King since it's the merging of the rune H for Harald with the rune B for Blåtand:

(source: redice.tv)

Cool eh?