Basic system of units concept  

We will Study here measurement of units that time every country was developed their own measurement and unit, India, France, America, Britain all were doing their own measurement like in India we were using hand for length measurement in India Land measurement unit use "Katha", Bigha in different area and convert to other unit and all this unit does not recognize each other this become problem for us. 

The main problem was that all country were using their own measurement system this was a communication gap of language so in international trade unable to trade, take an example suppose in India Petrol rate is 60 Rupees/litter but in America suppose 6 $/gallon if we purchase form Russia suppose 8 ruble/pound now question arises which one is costly among these three unit this became a problem for scientist.                                            

Basic system of units concept  

Now after that an International aviation Aeroplane started to move from one country to other country Suppose from India flight take off for America after reaching in zone of America ATC ( Air traffic Control ) give instruction to pilot keep your speed 300 miles/hour next station France instruct keep your speed 400 km/hour then what does pilot understand i am increasing my speed 300 hundred  to 400 hundred whereas 300 miles/ hour is greater speed than 400 km/hour then in this scenario pilot can confused and may be accident, similarly when we instruct pilot about pressure different country have different unit for pressure, pilot does not understand and this language problem is a very big problem 5 years ago an accident had occurred in last Inquiry found that pilot was Russian and does not understand the instruction given to him this was language problem so this is very much important that we should fixed a unique measurement system in the whole world for international trade, aviation and computer now we all know what is meaning of delete, page in ms word computer, without the help of unique measurement system we can't purchased anything from market and aviation is the safety for human life take an example i am looking for buy 2m rope asked shopkeeper how much money for 2m rope he is saying that 7rupees/kg so what is necessary the language of communication should be common so same problem we were having with measurement so it was necessary a common measurement of quantity those time three system was prominent because they were involved in business.

1 CGS System:

In this system we were measuring length in centimeter mass in gram and time in second this was popular in France,after scientist study and made definition it was found that is very small unit and also found this was very convenient method why convenient because of metric system (the unit which is next higher or lower is based upon the multiplication or division by "10") no any number was to remember in this unit when we multiply gram by 10 it becomes 10 gram (deca), again multiply by 10 then 100 gram (hecta), again multiply by 10 that become 1000 gram (Kilogram ) similarly 1 gram divided by 10 gives 10^-1 deci gram, again divided by 10 gives 10^-2 milligram so on hence only you have to remember 10 so it is metric system.    

2 FPS System: 

In this system we were measuring length in foot mass in pound and time in second this was popular in England this is non metric system you have to remember all number and its unit this was disadvantage of this system like 12 inch is equal to one foot, three feet equal to one yard so here we have to remember number and it unit this is main disadvantage of this system.hence we introduce a new system for development FPS system.

3 MKS System:

In this system length measure in meter mass in kg and time in second practically this system was good because large values was calculated easily in this system unit made large quantity becomes small here we have developed only three quantity for measurement that is for length, mass and time but latter on we added temperature then how temperature will be measure through this unit so we can't measure though this unit therefore our quantity increases for measurement for example someone say today shining of sun is much so how we can measure shining with help of only three quantity length, mass and time so our one new quantity is added, scientist sit together and more quantity added that is seven plus two total nine so we have finally nine quantity for unit measurement now all scientist of world made a committee to developed all nine quantity unit for measurement that committee name was General Conference on weight and measurement in 1971 committee ensured all member of world will follow this language for measurement this committee made unit for 9 quantity made these quantities definition and hold their sample in lab and every four years they sit together for improvement and addition and any changes in 1971 only seven quantities were added after 8 years latter they added two supplementary angle so its named as supplementary science this system was international so its named as system the international and called as S.I System in this S.I system scientist adopted basis of MKS System the unit which was present in MKS system adopted and the unit which was new scientist made for International hence this S.I System developed scientist added some properties in this system so that we can made this system better and further addition.

S.I System
SL	Quantity	Symbol	Unit	Symbol
1	Length	L	metre	m
2	Mass	M	kilogram	kg
3	Time	T	Second	s
4	Electric Current	A	ampere	A
5	Temperature	k	Kelvin	k
6	Amount of Substance	mol	mole	mol
7	Luminous Intensity	cd	Candela	cd
8	Plane Angle		radian	rad
9	Solid Angle		steradian	sr

                                          

Advantage of SI System:

1 It is a metric System it mean that we don't have to remember number only multiply and divide by 10 for next lower and higher number.

2 It is a coherent(Logical) system in this all derived units are made by multiplication or division of single units no numbers are required to remember example how one newton force is define take one kg of mass apply force so that it acceleration becomes one metre per second square this become one newton force, how one joule energy is define take one kg mass acceleration of one metre square per second for displacement one metre length this is one joule of energy so its become very simple no any number to remember for definition take one, one, one.

3 Rational system when scientist study deeply they found that we study one quantity in different place in different form take example mechanical energy(when body moves), heat energy(when water is heated), light energy(when light travels from sun), sound energy(sound in the form of wave), chemical energy(when reaction takes place between two molecules),when water is heated by one degree Celsius it is heat energy its unit calories when one watt of heater use for one hour how much of energy is used one kwh this is unit of energy, when one kg of mass having acceleration one metre per second square for displacement one metre is one joule so all having different units but all are energy only these forms are changing so scientist were converting from one form to other form but in SI system scientist chosen only one unit from these for energy that is joule now only joule will be used for energy unit.practically we don't use but SI system convey to use this unit one unit for all types of quantity so this is called rational system.

4 Easy and applicable to use all branches this unit will be use in chemistry, mechanics, biology and it is applicable to all the countries.

History of Unit Measurement:

Length Base Quantity length unit meter symbol ( m) now we will see how one meter length is defined, in ancient we made scale of rod taking length of a king from his nose to hand finger tips and same length of road was distributed in the world for one meter length some years uses this scale but scientist was not happy with this unit because they thought if by any means that length is destroyed in earth quack and now king is not alive or may be alive but can die latter then our unit will destroyed how world will use for measurement that time and it is also not possible to reproduce this unit because king is not alive and our sample already destroyed in the earth quack then scientist thought new unit scale using earth they measure the earth length from north to south and divided this length in many small parts and taken a small part of this length and called now this will be our one meter length now our problem is solved for reproduce whenever our sample is destroyed again we can measure the length and can reconstruct our length unit now you can think we can take any fixed rod of length and named as one meter wait Einstein theory say that any length depend upon moving speed if a rod is moving its length will increase whether it will be very little but increase then our earth is moving so our rod length will increase when we will go for other planet measurement its length will be different so our standard unit is not accurate some time passes scientist was also not happy they thought if earth is destroyed and that time suppose we are living on other planet then how we will use our measurement for length then scientist thought there should be something which can't change anywhere and can't destroyed then they thought natural quantity light its speed is constant everywhere in universe if we go to other planet and measure the speed of light will be same and it is also available everywhere easily can be reproduce anywhere if earth is destroyed life is possible we can live on other planet but if light is destroyed then human life will not presence then no meaning of universe and measurement so finally light is taken for unit of length measurement and it is define as the meter is the length of the path traveled by light in vacuum during a time interval of 1/299792458 of a second.

Kilogram basic quantity of mass represented by unit kg now till we have not related kilogram with universe object, kilogram first definition was made and still date it is continue and defined as the kilogram is equal to the mass of international prototype of the kilogram kept at international bureau of weights measures at serves near Paris France it is made by platinum iridium.

Time now time measurement was difficult due to speed, time was not counted properly take example one aeroplane is flying in air we have made two pillar fixed point we are observing time to cross this two pillar by aeroplane from ground suppose aeroplane takes 10 second to cross this two pillar now next day i am at platform which is moving in opposite direction of aeroplane now i count and its take 12 second to pass this two pillar here we have counted 12 second in other case because our moving platform not consider as for example we are standing on the earth but earth is moving but we did't see earth is moving if we count from earth other object time then it will be correct or wrong of course it will be wrong because earth is moving so no correct time for anything hence it become big problem for real definition of unit, we was made that every 24 hours sun arises divide this time into 24 parts one part will be of one hour again divide into 60 parts one part will be of one minute and again divide into 60 parts one part will be one second but after knowing earth is moving this method became wrong and we accept this is wrong then what will be one second go for new definition then scientist thought what is that thing which does not change in this world then its answer was light and define as the second is the duration of 9192631770 periods of radiation corresponding to the transition between the two hyper fine levels of the ground state of the cesium 133 atom.now we will see in depth how light is created take an atom of electron as we know electron is moving outer orbit when we given some energy then electron moves to some next higher level energy but know every electron orbit is fixed on the basis of energy level then that electron try to comes in its original orbit level where it was previously but suddenly it will not come now it start oscillation and make oscillation between higher energy level to its original energy level and continuously moving every oscillation has some frequency and slowly it makes 9192631770 oscillation to settle down in its original orbit because it has to live in its own orbit. this is just like simple pendulum when we released a simple pendulum from its mean position then pendulum start oscillation and slowly settle down its mean position its energy released in air dragging  then where does that energy gone which we have given to this electron now this energy is released by electron in the form of light which we observed through our eyes this sensation happens through brain and observed through eye other parts of body are unable to observed if its frequency will be slow then light will be not observed because no sensation will be observed by eyes or brain just like when we push TV remote its frequency is low so we can't see but it on the TV every object has its own natural frequency we can't change its time period of oscillation every material has different oscillation frequency so we have taken cesium 133 atom when electron made 9192631770 oscillation we told one second competed so this time is called one second its oscillation time never change so our time will not change with speed whether it is moving anywhere in universe so speed of light is not change in anywhere in universe because its oscillation is fixed so this is called cesium clock now its error is very very less because it oscillation is very large this error may be 1/9192631770 cesium clock this accuracy must be required when we send our space shuttle to Mars otherwise shuttle can go other place in very few second change so think how many years will take to change one second in cesium clock thanks for reading 

Basic system of units concept .