The definition and importance of Earth's gravity Gravity are one of the factors that help sustain life on Earth, as Earth's gravity works to maintain the distance that exists between the Earth and the Sun, and this distance is also known as the Earth's orbit, as this distance is a reason for The survival of modesty on planet Earth, and from these data, we will shed light for you through our following lines on the reference site to explain the answer to the question posed, and to address the gravitational field.

## gravity

Gravity is considered to be the cosmic force of attraction that arises between all substances. It is known as the force of attraction that arises between two objects, as all objects in the universe attract each other.

This force is also the weakest among the types of cosmic forces, as it does not play a role in determining the internal properties of materials, but is characterized by its far-reaching and cosmic influence, as it controls the paths of objects in the solar system or other places, as well as controls the development of stars, galaxies and the entire universe.

## Define Earth's gravity?

Earth's gravity refers to one of the characteristics of the planet Earth that works to attract all objects towards its center as a result of its huge mass, as there is an attractive force between objects and Earth's gravity is characterized by attracting all objects towards it with an acceleration of 9.8 m/s², and Earth's gravity occurs as a result of the Earth's mass As it attracts all objects in the universe about its mass and the relationship between the inverse square of the distance between their centers, it affects outer space and prevents objects from falling and derailing its path, and the acceleration of gravity on the surface of the moon is estimated at 1.6 m/s².

## The importance of gravity

The Earth's gravity is very important, as bodies burn from the sun and cannot survive and live on the face of the earth, and the reasons behind its importance will be explained below:

- Gravity binds the world together.
- Gravity is what keeps the planets in their orbit around the sun.
- Ocean tides are caused by the gravitational pull between the Moon and the Earth.
- Gravity strengthens the body's immune system. In weightlessness, muscles weaken due to less use, so astronauts have to exercise every day.
- Gravity maintains the vital roles of the body and the distribution of fluids in the body, so astronauts suffer from headaches and circulation problems.
- Earth's gravity maintains the existence of the atmosphere that surrounds the Earth, as it is what keeps living organisms able to breathe and live.
- The Earth's gravity keeps the Earth in its orbit, helping to maintain a proper distance between one another and enjoy the sun's rays.

## The history of gravity

Isaac Newton is considered the first to discover gravity in 1687 when he was sitting at the bottom of an apple tree and noticed the apple falling, and then tried to find out why it fell down instead of its direction to the right or left or even ascending to the top, where That this reason is represented in an unknown force that pulled it down, as Newton later called it gravity and developed the theory of Newton's law of universal gravitation, and then Albert Einstein came in the twentieth century, where he gave a new idea about gravity, which is a falsification of time and location.

## unit of gravity

Gravity is considered one of the fundamental forces in the universe, where it is possible to measure the force of its impact and infer its unity through Newton's basic law for measuring force, which is force = mass * acceleration, so the unit of gravity can be determined by mentioning the special unit for each of the variables mentioned in the equation, and the unit of measurement for mass is the kilogram. As for the measurement of acceleration in meters per second squared, when the units are applied in the equation, the unit of gravity becomes kilograms * meters per second^2 which is referred to as the newton unit.

## Gravitational field concept

The gravitational field is defined as the force that exists in the space around a mass or a group of masses, and the field extends in all directions and its amount increases and decreases depending on the distance between objects, where the gravitational field is measured in force units per unit mass, and the unit is often used Newtons per kilogram, and this field is characterized as one of the types of force fields, as it is determined by the following relationship (gravitational field = general gravitational constant x body mass / square distance), and the gravitational field around objects can be explained in two ways, which are as follows:

- Arrows: The arrows indicate the amount and direction of the force at different points in space. The longer the arrow, the greater the force.
- Field lines: The field lines indicate the direction of the force acting on a body located in a specific place in space, where the amount of field is indicated by the spacing of the lines.

## Galileo's theory of gravitation

The scientist Galileo Galilei threw things from the top of the Leaning Tower of Pisa, such as silver, gold, wood, and balls, and he also expected that heavy objects would fall to the ground at a faster speed than light ones until they all hit the ground at the same time. Thus, the scientist discovered that gravity contributes to the acceleration of all objects at the same rate despite From mass or components, then this result was called free fall or the equivalence principle, as it is known as the cornerstone of modern physics, as the scientist Albert Einstein developed the general theory of relativity assuming the validity of this principle, and modern theories suggest that gravitational acceleration depends Exactly on the components of materials for objects, and when stating the validity of this information, the theory of relativity must be reconsidered.

## Newton's theory of gravitation

The concept of gravity appeared in the English mathematician Isaac Newton in the sixteenth century, as it revolves around the world sitting under apple trees and the fall of one of its fruits on his head, which led him to think about the reason for its fall to the ground directly, and then published his theory of gravity In the eighties of the sixteenth century.

## Newton's law of gravitation

Newton's law of gravitation shows that any two bodies in the universe have a force of attraction between them, where Newton put the law of gravity in 1687 and used it to monitor the movements of the planets and their moons, and the mathematical formula of the law is: (gravitational force = product of the mass of the first body x the mass of the second body x constant General attraction ÷ square of the distance between the two bodies), and in symbols, it is written in the following form: (S = K1 × K2 × W/F²), as these symbols can be explained as follows:

- K1: the mass of the first body, in kilograms.
- K2: the mass of the second body, in kilograms.
- s: the universal gravitational constant, equal to 6.67408 x 10^-11 newtons.m²/kg².

## Einstein's theory of gravity

The scientist Albert Einstein was awarded the Nobel Prize in Physics in 1921, for he contributed to an alternative theory of gravity in the nineteenth century, as it was part of the general theory of relativity, and it also contained a different interpretation of what Newton's law came in defining gravity, as Einstein He did not believe that gravity is a force and referred to it as a curvature of space-time and called it the fourth dimension, and the following will be explained what is the difference between basic physics and Einstein’s theory:

## Basic Physics

Fundamental physics is defined as the absence of an external force acting during work, which leads to the body traveling in the most straight line, and according to this any two bodies that are in parallel paths always travel in parallel, they never meet even though they do not actually meet, but the passing bodies end With parallel paths in collision at times, Newton explains the occurrence of this act by gravity, as it contributes to the attraction of bodies to each other or to a third body.

## Einstein's theory

Einstein explains in his theory that the two traveling bodies keep staying in the most straight lines, until these two bodies turn into spherical paths due to a curvature in space-time, meaning when two bodies move on a flat plane because they will move in a spherical plane and the straight paths end near-spherical paths At a certain point, as the difference between Einstein's theory of defining gravity in general and Newton's theory in basic physics that he does not treat gravity as a force, but rather is the curvature of spacetime, which leads to this collision.

## The relationship between gravity and the factors affecting it

The concept of gravity can be used to know some of the factors that depend on it and affect it, as both the mass of the body and the distance between the centers of the bodies and their shape are the main factors on which the amount and value of the earth’s gravity depend, and the effect of the factors on the earth’s gravity will be explained below:

## The relationship between gravity and altitude

The value of Earth's gravity changes depending on height, as it is proportional to the relationship 1/n^2, the 0 symbols (n) refers to the distance from the center of the Earth, and as the value of the radius increases from the center of the Earth, the value of Earth's gravity decreases, that is, it decreases with Altitude, for example, the value of gravity that attracts an aircraft flying at a height of 40 km from the earth's surface will be less than the value of gravity at a lower altitude.

## The relationship between gravity and distance

The definition of gravity shows the relationship between its value and each of the mass of attractive bodies and the distance between them, as the value of the force of gravity is inversely proportional to the square of the distance between the two attractive bodies, for example when the distance between the two bodies decreases, the value of the force of attraction between them decreases, but when Reducing the distance between them, the value of the force of attraction increases.

## The relationship between gravity and mass

The concept of gravity indicates the use of the physical law on its relationship with mass, as the mass of bodies is directly proportional to the value of the gravitational force. From the two attractive bodies, the gravitational value increases fourfold.

## Earth's gravitational effects

Earth's gravity affects all objects that exist in the universe, and it also affects objects that are found on planets and stars, as it has many effects on the planet and living organisms, and the following will be shown the positive and negative effects of them:

## Positive effects of gravity

There are many positive effects of Earth's gravity as it has a fundamental role in human life and existence, and it is considered one of the basics of life on the surface of the planet and cannot continue without it. Among the positive effects of Earth's gravity are the following:

- Promotes calcium production.
- Promotes ripening in plants.
- Contributes to the management of fluid flow.
- Allow rain to fall on the ground.
- Maintains muscle and bone function.
- Firing in a predictable direction.
- It allows the planet to maintain its atmosphere.
- This constant force keeps objects in place.
- It maintains the survival of humans and other living creatures on the surface of the planet.
- Its energy is stored in the form of potential energy that allows the exploitation of resources such as hydro dams.

## Negative effects of gravity

Gravity is known as one of the basic components of the planet, where life cannot continue without its presence, and despite its many positive effects, there may be some negative effects, and the following will be shown the negative impact of gravity:

- It makes the aero-car industry difficult.
- Limit the height of buildings that can be built.
- It affects the skeleton, especially with age.
- It makes it possible for people to fall to the ground and hurt themselves.
- It allows the attraction of huge rocky bodies or celestial bodies that lead to catastrophic effects if they enter the atmosphere.
- Contribute to keeping humans on planet Earth, where it is difficult to travel to outer space easily and at a little financial cost.

## How to calculate the gravitational force between objects

Gravity is considered to be one of the basic types of forces in physics, as it is of particular importance because it is cosmic, in addition to its importance in the life of the individual, as calculating its value is one of the important things in physics. grams and the Earth, knowing that the mass of the Earth is 5.98 * 10^24 kilograms, and the value of the gravitational constant is 6.673 * 10^-11:

- Using the definition of gravity, which is the following mathematical equation: gravitational force = “g * k 1 * k 2” / “m^2”.
- Use the metric system of units, where the unit of mass must be the kilogram and the unit of distance is the meter.
- Measure the value of masses for objects, and the value of small masses can be measured in grams. In the previous example, as 1 = 68 kilograms, and as 2 = 5.98 * 10^24 kilograms.
- Measuring the distance between the attractive masses, where the value of the gravitational force between a body and the earth should be calculated, the distance will be determined by the distance of the body from the center of the earth, where the approximate distance between the surface of the earth and its center is 6.38 * 10^6 meters.
- Put the variables in their exact place from the mathematical equation and find the result as follows: gravitational force = “6.673*10^-11*68* 5.98*10^24″ / “6.38*10^6″, and the result in this example is 665 Newtons.

## facts about gravity

Gravity is known as the weakest of the fundamental forces that have been known in nature, yet it is considered one of the dominant forces that work on the cohesion of the universe, galaxies, and solar systems, and the following will be among some facts about Earth's gravity:

- The weight of a person is the force of attraction between him and the ground.
- The force of gravity on Mars is about 38% that of Earth.
- The force of gravity on the Moon is about 16% of the force on Earth.
- Black holes are considered to have a gravitational pull so strong that even light cannot escape them.
- The velocity of free fall is a constant velocity on the surface of the earth, which is that all things fall at the same speed, and this velocity on the surface of the earth was calculated to be 9.8 m/s.
- The best estimate of the gravitational constant G is currently considered to be approximately 6.67259 x 10-11 Newton-meters per square kilogram.
- Gravity depends on the size and mass of an object, and the greater the mass, the greater the gravity.
- Anybody can escape from the force of Earth's gravity if it moves at a speed of 7 miles per second, which is the escape speed of Earth's gravity.
- The force of gravity is one of the weakest forces in nature, as it plays no role in determining the internal properties of everyday matter.
- Dropping an iron rod with a feather promises that they will both fall at the same speed without any difference, gravity has the same effect on all things however different they are.

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