Gravity

We barely think about gravity in our daily lives, but we must realise that it defines how we interact with the world. We grow within its constraints, and our heart, muscles, and balance system depend on it. Gravity is one of the fundamental forces of the universe. In this article, let us understand what gravity is and its effect on us.

What Is Gravity?

Every object that has mass exerts a gravitational pull or force on every other mass. The strength of this pull depends on the masses of objects at play. Gravity keeps the planets in orbit around the sun and the moon around the Earth. Hence, we define gravity as:

Gravity is a force that attracts a body towards the centre of the earth or any other physical body having mass.

History of Gravity

• In 1687, Sir Isaac Newton first discovered gravity. While sitting under an apple tree, he noticed an apple falling down. Then he tried to figure out why the apple came down instead of going up or left or right. In this situation, there was clearly an unknown force at play. That force is what Newton called gravity, and his theory is called Newton’s law of Universal Gravitation.
• Later in the early 20th century, Albert Einstein developed a whole new idea about gravity. According to him, gravity is the warping of space and time.

Gravity in Universe

After understanding what is gravity, let us know how gravity plays a major role in sustaining life on earth. Because of the gravitational pull between the earth and the sun, the atmosphere is kept in place and provides us with the air we need to breathe to survive. It also keeps us safe from the sun, allowing us to enjoy the sun’s light and warmth.

 

Measuring Gravity

Sir Issac Newton defined the force of gravity as follows:

“Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.”

Mathematically, this translates to

represented as:

Fg = mg

Where,

• F is the force,
• m1 and m2 are masses of the objects interacting
• r is the distance between the centre of the masses
• G is the gravitational constant (6.674×10−11 m3⋅kg−1⋅s−2)

This equation gives the magnitude of the force, and since it is an attractive force, it will always be directed towards the other object. From the above equation, we can come to the conclusion that anything that has mass has gravity. Objects with heavier mass have more gravity. The closer the two objects are, the heavier the gravitational pull between them. Gravity gets weaker with distance. The above formula is used to calculate the gravitational force between two objects.

Gravity on Earth

In comparison with other celestial bodies, the Earth has an average gravitational pull. Various locations on the Earth exhibit gravitational fields smaller or larger than average. This is mainly due to mass variation (higher or lower matter distribution) across the planet. Gravitational force is the force that builds an attraction between two or more bodies. The objects with less mass have a weak gravitation pull, while the objects with larger mass have a stronger gravitational pull.

Objects are held down to the ground because of the gravitational force of the Earth. Objects actually exert a force of gravity on the Earth. Since every object on the Earth has very less mass than the Earth, the gravitational force exerted by such objects is negligible compared to the Earth’s gravitational pull. The average gravitational force of the Earth is 9.8 m/s2.

Examples of Gravity

After knowing what is gravity, let us have a look at a few examples of gravity at work are:

• The gases in the sun are held together by gravity.
• Gravity is responsible for water resting at the bottom of a glass instead of hovering over at the top.
• The force of attraction between the earth and the moon causes tides in the ocean. This is the result of gravity.
• Gravity causes the moon to revolve around the earth.

Gravity has the same effect on all objects. If you drop an iron road and a feather, they will fall at the exact same speed. Due to the effect of air resistance on gravity, it might look like the iron rod falls at a greater speed. However, if they were dropped in the vacuum, they would fall at the exact same time. The gravity of an object depends on its size. To be more specific, the Gravity of an object depends on the mass of that object. It is undoubtedly the weakest known force in nature and thus plays no role in determining the internal properties of everyday matter.

Relationship between Gravity and Weight

Weight is defined as the force with which a body is attracted to the earth by gravitation. It is just another word for the force of gravity Fg. Weight is a force that acts on all objects near earth. The weight of an object can be calculated by multiplying the mass of the body with the magnitude of the acceleration due to gravity (g = 9.8 m/s2).

Mathematically, it is represented as:

Fg = mg

Where,

• Fg is the force of gravity
• m is the mass of the object
• g is the acceleration due to gravity

Many people confuse mass with weight. One must keep in mind that mass is the measure of how much the body resists velocity, in other words, the object’s inertia. Although they are closely related to each other, they mean different things. The mass has units of kg, whereas the weight is a force and has units of N.

Facts About Gravity

• Gravity is the weakest of nature’s four known fundamental forces, yet it is the most dominant force. Even though it is the weakest force, Gravity holds together the entire solar systems and galaxies.
• The free fall speed is consistent over the earth’s surface. This means all objects fall at the same speed. This speed on earth is calculated to be 9.8 m/s.
• The best current estimate of G is that it equals about 6.67259 x 10-11 newton-square meter per square kilogram.
• The force of attraction between you and the Earth is your weight.
• An object must travel 7 miles a second, i.e. the earth’s escape velocity, to leave Earth’s gravitational pull behind.
• The gravitational force on the moon is around 16% of that on Earth, Mars has around 38% of the Earth’s pull, and Jupiter has 2.5 times the Earth’s gravity.
• Black Holes are the places in the universe that have strong gravity that even light cannot escape from it.
• Gravity can bend light!
• According to Einstein, gravity is not a force.
• Gravity might be the weakest of the four fundamental forces, but it has an unlimited range.

Gravity is very important to us. It wouldn’t have been possible for us to live on earth if it weren’t for gravity. The sun’s gravity keeps the earth revolving around it, keeping us at a comfortable distance to enjoy the sun’s warmth and light. Ultimately, gravity is the glue that holds the cosmos together!

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