Here are two articles about inventions that were listed Book Review: The Greatest Inventions of the Past 2000 Years book that I wanted to note down in my blog for future reference.

The reason I wanted to note down is, I personally find that numeric system that we use today has stood the test of time and is limitless. And my second reason could be due to a emotional attachment and association that is imbibed in me.

V. S. Ramachandran

My favorite invention is the place-value notation system combined with the the user of a symbol 0 for zero to denote a nonexistant number; this marks the birth of modern mathematics. This system was invented in India, probably during the first millennium before Christ, but was first systematized by the Hindu mathematician and astronomer Aryabhata I at the tail end of the fifth century and then transmitted to the West via the Arabs (hence the phrase "Arabic Numerals"). Before this time, even simple arithmetic was tedious and time-consuming (as when the Romans and Greeks used the cumbersome "Roman numerals" - sometime still used in the west). And math, of course, is essential for all science. Without the early invention of zero and place value as well as the use of the a symbol to denote an unknown quantity in an equation (algebra), also from India, subsequent developments could not have occurred. There would be no calculus, no newtonian or Galilean science, no computers, and essentially no modern world.

Keith Devlin

"What is the most important invention in the past two thousand years?" is one of those questions that no correct answer - like "What is the best novel / symphony / movie?" - But if I had to make a choice, it would be the Hindu-Arabic number system, which reached essentially it's present form in the sixth century. Without it, Galileo would have been unable to begin the quantificational study of nature which we now call science, and we would not have had calculus, another major invention of the period in question.

Before of it's linguistic structure, the Hindu-Arabic number system allows humans who have an innate linguistic fluency but only a very primitive number sense to use their ability with language to handle numbers of virtually any useful magnitude, with as much precision as required. Today there is scarcely any aspect of life that does not depend on our ability to handle numbers efficiently and accurately. True, we now use computers to do much of our number crunching, but without the Hindu-Arabic number system we would not have any computers.

In addition to it's use in arithmetic and science, the Hindu-Arabic number system is the only genuinely universal language on earth - apart, perhaps, from the Windows Operating System, which has achieved the near universal adoption of a conceptually and technologically poor product by the sheer force of market dominance. By contrast, the Hindu-Arabic number system gained worldwide acceptance because it is far better designed and much more efficient for human usage than any other number system.

I have personally been annoyed when I cannot find solution to hard problem. I used to think that "looking up" for an answer is not being honest. That stance may not help. After trying, I think, a student (like me), could benefit by looking up the answers for hard problems, and try to emulate it.

Found this in the words a professor giving advise to his students.

Students join forces on the problem sets, and some students benefit more than others from these weekly collective efforts. The most brilliant students will invariably work out all the problems and let other students copy, and I pretend to be annoyed when I learn that this has happened. But I know that by making the effort to understand the solution of a truly difficult problem discovered by one of their peers, students learn more than they would by working out some less demanding exercise.

From 10 Lessons of an MIT Education

I started reading this book using a hardcopy that I had for long time. For convenience, I quickly finished by reading the online ebook at Project Gutenberg . Since I read fast, I did't enjoy this very much. Won't discuss this much.

It seems like the developers of Civilization V once decided to store aggresiveness index of leaders in a unsigned int. And Gandhi, as the most pacifist leader that he was, was assigned lowest number 1. Also, in the game play if a society adopted democracy, the aggresiveness score was reduced by 2.

So, when Gandhi adopted democracy, his aggresiveness score became 1 - 2 = -1, and as it was unsigned int, and it gained a very high value.

#include<stdio.h>

int main(void) {
    unsigned int i;
    i = -1;
    printf("%x\n", i);
}

$ clang unsigned.c
$ ./a.out
4294967295

And thus Gandhi was ready to nuke whenever there is a conflict.

Looks like Google celebrated Subramanya Chandrasekhar's 107'th birthday with a doodle. I had missed it, so I got excited to go check it out again.

The doodle is amazing! It illustrates the concept of a star when it gains 1.4 times the mass of sun will turn into white-dwarf and eventually into a black-hole!

Chandrasekhar discovered this, and it is known as Chandrasekhar's limit.

This seems like a typical my-thing. I've fallen into this trap many times. It looks people in my profession fall prey to this too.

That’s one reason I don’t miss IT, because programmers are very unlikable people… In aviation, for example, people who greatly overestimate their level of skill are all dead. - Philip Greenspun, co-founder of ArsDigita, excerpted from Founders at Work.

https://github.com/anders94/blockchain-demo is the simplest and most intuitive explanation of blockchain that I have come across so far. In the very short YouTube video, the author guides us through starting with a hashing function, a block, the concept of a signature in the block, then a blockchain, a distributed blockchain, the concept of immutability in the blockchain and the distributed blockchain, recording transactions in the blockchain, and verifying transactions in the blockchain.

Some exciting learning here with this book. I learnt about the following:

• https://en.wikipedia.org/wiki/Cygnus_X-1

• https://www.nasa.gov/mission_pages/chandra/multimedia/cygnusx1.html

• https://en.wikipedia.org/wiki/Chandra_X-ray_Observatory

• https://en.wikipedia.org/wiki/Schwarzschild_radius

• https://en.wikipedia.org/wiki/Karl_Schwarzschild

A billion years is some- times called an eon, so that we may say the Earth was formed 4.6 eons ago.