Paper 6

Gravity variation from the equator to the poles.

Ramin Amir mardfar


Gravity variation from the equator to the poles.

Rotation of earth around itself causes a centrifugal force on things, which is on the opposite direction of gravity and causes to decreas of weigh of them. This force is more stronger in equator, so weight of a thing in there is a littie lighten then the weight of the seme thing in other point of the earth. The escape from center force causes that while a thing has 1000gr weight in the pole, it will be 996gr in the equator. in other words, we see about 4gr decrease per kilogramm. Thats, one person with 70kg in the pole, will be 69.7kg in the equator. The latitude of the pole is 90� and 0� for the equator. If we transfer a thing with 1kg from latitude of 45� to the equator difference of weigh for per kg will be less than 4gr. Therefor we see that the changs of gravity on the earth isn't so much and causes in significent difference in thing's weight. In 1671 an astronomer group set off from Paris (45� north) to Cayenne island (5� north) for a commission. Jean Richer, the head of this group, had a precise pendulum clock with him in this trip. He noticid that clock was postponed 21.1 minutes per 24 hours. Richer didn't know why. But about 15 years later, Issac Newton said that the reason, is the difference of gravity in the mentioned zone. After tath, pendulum bacame a precise facility for measuring difference of gravity in various points of the earth. Becouse in near places to eaother, spring-balance coudn't show insignificant difference of gravity but pendulum couldeasly. It seemed that pendulum can make visual differences like a magnifying glaas. How a pendulum can do such a work? When we weigh a thing with a spring-balance, and compare the difference of weight with other zones, we only have done this once and registen therefore, the differens will be little and insignificant. It pendulum moves only once, the difference of time, will be shown much little. i.e. difference of time for moving of pendulum once in equator and pole is significant and showe the same little difference of the spring-balance. But, when pendulum moves twice (go and return) it will delay little each time and because of gather together of these, we will see the difference twice larger. i.e. pendulum has magnifyed it twice, so we can see it easier. If pendulum moves three times, the difference will be threefold. Because of delay of pendulum each time (go and return), in therr times (go and return) it will delay three times and these differences will collect on each other and it's shown threefold finally.
So it's possible to compare the difference of gravity in varios zones with each other. Because the of pendulum's move (go and return) to being the magnification more, and can register and study much little difference of gravity in neibour zones simply. Imagine if pendulum go and return once per second, has many times it'll go and return in 24 hours and it's possible to obtain the magnification. This great magnification was that noticed Jone Richer in 1671 to the difference of gravity in Paris and Cayenne island. While if he wanted to do this test even with the most precise balance of that time, he coudn't get a conclusion and coudn't show any difference of gravity between Cayenne island and Paris.
There is a set similar to a pendulum in animals body which show's the little difference of gravity with a great magnification. This set, is the same blood circulation system with motive factor of heart. Blood is moving like pendulum alternately. Each round of circulation of blood is similar to onetime go and return of a pendulum. Blood, keeps aloof from the surface of earth alternately like a pandulum and comes nearer to it again and repeats this duty hundreds of time each day and night. So, the little difference of gravity will have a lot of effect in work of this set as well as it had in work of a pendulum. If blood circulatory only once during the life of an animal, the little difference of gravity couldn't impress on it and acted as a spring-balance. But because blood goes up and down from the surface of earth in thowands of time, so like a pendulum, the effect of little difference of gravity in this set will collect thousand of time and will be a great amount.
Let's suppose, an animal has one kg in it's body and it's heart circulates this blood a round in it's body per 10 seconds. Let's suppose we transfer this animal from the equator to a place near to the pole. There, it's blood will be heavier about 4gr. i.e. it's heart must enter 4gr additional force when it wants to cary the blood up and return it. If it did this only once, it hadn't any problem. But the heart of this animal, repeat this oer to secondes i.e. 24gr per minute or 1440gr per hour or 34560gr per day and night i.e. the heart of this animal in the pole, must carry 34.5kg more load than equtor.
If animal be larger and have more blood, this additional load will be more than this too. Therefore we see that, with a much little change in gravity it be imposed a lot of additional force to the animal's heart. This is why tall and big animals such as giraffa and elephant can only live in equatoral pionts of earth, because of less gravity in there (little amount) than other places and their heart can send blood to farther distances from the surface of earth. So in practice we see that much little increase of gravity has noteworthy effect in animal bulk.

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