### A small thought about gravity.

Reading BBC Focus (July's issue), I suddenly found out an astonishing thing about gravity. To be honest, I was really surprised, because an underlying base was not something novel to me at all, but a consequence was.

Well, I will rewrite an John Gribbin's idea in my own words. Consider a star, contaning the tremendous count of particles. If they spread out to infinite distance, then their overall gravitational energy would be zero, because gravitational energy of two particles is proportional to 1 divided by the square of the distance between them. As all distances would be equal to infinity, gravitational energy of interaction between all particles would be equal to zero. But if these particles fell together in the proposed center of the star, kinetic and heat energy would be unleashed from gravitational interaction.

What does this magic mean? Being started out with null, the very gravitational field ended up with less than null energy! What is more, if the particles would be placed into one point, all released according to the prominent Einstein's equation mass-energy would be exactly equal to the energy of the negative gravitational field! That is the point where scientists now think our university began its life.

### Who is Mr.Tesla?

Adjectives describing genius and talent frequently appear when the name of Nikola Tesla comes up in a conversation. But let's think of for a second – why? What did he invent or discover so that everyone considers him as one of the most clever and ingenious human ever living on the Earth? I would like to present my own sight on this puzzle.

Regard to a work.

I certainly believe there is one simple thing every successful life is based on – working on yourself. Being exceptional scientist and engineer, Nikola Tesla was not exceptional for this rule. As we know he was extremelly hard-working person, doing his business from 9:00 a.m. often until 3:00 a.m.! There were letters from his proffesor to his father warning that Nikola would die due to overworking if he resumed to work so much time. Also he claimed that he never had a dream for more that two hours. He could work in his laboratory for two or even three days without any sleeping.

Ideas.

They were crazy. Even nowadays some of them seem to be mad and then they were absolutely crazy. What will you say if someone tells you that he has decided to build a tower of 57 meters length to transmit enegry in a wireless way over the ocean? I suppose it won't be applied as a truth. And in my opinion this is the most astonishing part of him. He didn't fear to think different and turn ideas into reality even absent money or support. The more interesting thing about him is that his crazy ideas actually worked. And even that idea with power transmittion. All of designed by him equipments, facilities, motors and so on were able to do what they were supposed to do. Besides, his creativity couldn't be stopped, he even patented a biplane able to take off vertically. Moreover, his thoughts and speculations frequently were absolutely correct. For instance, the principle of radar was described by him in the magazine Electrical Experimenter. Even though his assumption that waves with high frequency could penetrate water was wrong, the general idea of usage of waves' reflections was right. As Emile Girardeau noted «If he was dreaming, at least he was dreaming correctly».

Personality and appearance.

As his contemporaries mentioned he was a self-confident and self-loved person with strange habits. His well-known weirdness was feeding pidgeons. Once he literally felt in love with an injured pidgeon. «I loved that pigeon as a man loves a woman, and she loved me» he said. This definitely contrasts with his appearance of tall (1.88 m) and serious scientist with big hands. Frankly speaking he gave his special attention to appearance and even the position during taking photos. His clothes were always neat and fit, he didn't wear any jewelry. Tesla was quite harsh and could criticize appearance of others with his inherent simplicity. The only negative opinion in the New York Times about Edison's death was written by him. In that article he blamed Edison in bad knowledge of physics and mathematics, claimed that he disregard rules of hygiene and said more other unpleasant things.

Would such a guy be wrong? Sure. Lots of his thoughts and assumptions were wrong. For example, he claimed that atoms were immutable and couldn't be divided in any way. His view of impossibility of existing of curved space was also incorrect. Of course from our point of view he seems to be an absolute genius, but he made his mistakes everyday. May it have been his life's secret?

### British Gravitational System.

A few weeks ago reading «Fundamentals of Aerodynamics» by Anderson (I strongly recommend this book for aviation geeks) I found a fascinating thing. It turns out that so-called British Gravitational System of units is commonly used in British engineering literature. That was rather surprising for me cause I thought we all use a standardized metric system – the International System of Units – regardless of country.

Appearing of the SI.

The first step toward the development of metric units of measurement happened in 1790s. Metre and kilogram were announced as base units. Of course, that system couldn't be considered as completed and consistent one. With the lapse of time second, ampere, degree Kelvin and candela were added to the base units, and finally in 1960 on the General Conference on Weights and Measures the International System of Units was established.

Derived units.

Units not included into the list of base units are supposed to be derived from base units. A simple example is measurement units in the Second Newton's Law: F = m * a. Suppose we would like to derive units of force. Considering «m» as kilograms and «a» as meter over second squared we consequently derive a unit of force as (kg * m) / (s * s) and rename it as N (newtons). N is called a derived unit. From our point of view it seems to be absolutely clear, but let's remember that the concept of mass was developed by Isaac Newton only in the end of 17th century and to be honest it was an amazing discovery in those times. Initially weight was measured as a base dimension basically due to its simplicity to measure. Newton proposed a linkage between weight and acceleration which was provided by constant mass. In his new concept mass was getting more fundamental unit. But despite of his findings, weight didn't lose its popularity as a unit of measurement. With the lapse of time the term of weight was replaced by pound force (lbf – a force that is equal to the gravitational force exerted on a mass of one pound on the Earth), but the idea of force-based system stayed the same.

SI and BGS.

British Gravitational System (as English Engineering System too) supposes lbf as a unit of force, foot as a unit of length and second as a unit of time. Mass may be derived from the Second Newton's Law, a unit of mass was called «slug». As you can see the system is very distinctive with comparison to the SI. Both systems are successors of Imperial system of measure which has dominated in the United Kingdom for a long time and even now it is not suprising to find out pounds and feet in common use. The International System was extremely convenient in the area of trade and this is the reason why SI was established at first as a default system in trade. The area of engineering was always much more conservative and hence it would be serious and long work to recalculate and review all papers to satisfy the novel SI. That state would be changed because of a important disadvantage of BGS – a strong link with gravitational acceleration. Unfortunately for BGS, its magnitude is not constant and can alter from 9.78 to 9.82 depending on altitude. Therefore if you carry out an experiment with measuring pound forces you will get different results in different sites. Undoubtedly, it is getting impossible to use BGS in the case of high precision requirements. But enginerring mostly doesn't require high accuracy and actually require a convenient way to measure things. This is the main secret of British Gravitational System's and English Engineering System's long lives. They are still widely used in engineering literature despite talks about their "senility".

### My first post and what will be going on

One day I came up with an idea to post all interesting stuff I got to know somehow. But also I thought it would be nice to post in English just for writing practice. That's why you are reading this one not in Russian despite I'm Russian. There won't be any political analytics or my dumb thoughts about things happening around the world (I'm lying, there will be a bit :)). All I want is just to tell about ideas, persons, stories, events that have had an impact on me. Hopefully it won't be too boring :)