So you want to know why you pull back to the ground every time you jump.
Well, this is gravity and here is the guest post about this from Mohit Kumar Rajput. He is the Bachelor in Physics (Hons.) student pursuing graduation from Delhi University and have a keen interest and passion in the Physics.
What is Gravity?
The gravity is the phenomenon by which a body is attracted towards the centre of the earth or in space towards other bodies having mass. It is an attraction force that exist between two objects for example, between Sun and Earth and between Earth and you.
We see many incidents related to gravity in our day to day life. For example if we are standing in a garden and throw a stone upward direction it comes back to the earth. This is due to gravity.
We generally use the logic of attractive force behind it. We think that earth is attracting all the bodies towards its centre with an attractive force. But Gravity is most accurately described by the general theory of relativity which describes gravitation as consequence of curvature of space and time.
Who discovered Gravity?
Sir Isaac Newton, the English mathematician, and Physicist discovered Gravity when he saw a falling apple from the tree. He realized that something is acting on the apple in downward direction otherwise, it would go directly into the space. Newton called this force Gravity and gave the theory that gravitational force exists between all the objects.
But Albert Einstein developed a new theory about Gravity. According to him, Gravity arises from wraping of time and space.
What is Space?
In simple terms, it is three-dimensional extent (height, width, and depth) within which all objects have their relative position and move.
What is Space-Time?
This world has four dimensions – three space dimensions and one is time. Space-Time is a mathematical model that combines space and time into a single interlaced continuous sequence. This is represented by Euclidean space which regards space having three dimensions and time consisting one dimension. By combining space and time into a single manifold many problems can be simplified significantly.
Gravity as a consequence of curvature of Space-Time
In physics, we always try to draw a practical picture according to the theory in our minds. For this, the realisation of curvature of the Earth is very necessary to understand this theory.
Fig. Distortion of the curvature of space-time by the Earth.
In above diagram, blue lines are indicating the Space-Time and Earth distorted them.
Let’s imagine. You are in a free space, there is no stars or planet. When a planet, let’s say Earth is created close to you, you wouldn’t feel any force. But you would feel that you started to move towards the earth. This is the case where you’re travelling through space. You may wonder that you are not travelled through time but people observing you are.
By the presence of the Earth, the distortion of Space-Time is caused, that accelerates your body in the direction of the center of the Earth when your feet are touching the ground. Actually, ground put on a force on your feet in the upwards direction, hence you are pushed in the opposite direction.
In simple words, you are being accelerated in the upward direction with respect to space-time by the force on your feet applied by the ground. Just by having your existence, you are bound to travel through space – that is gravity.
Top 10 facts about Gravity you should know
1. Gravity is the most prominent but weakest of four known forces of Earth. Other three are electromagnetism, weak nuclear force, and strong nuclear force.
However, it keeps entire solar system and galaxies together. Interesting Hmm!
2. The gravitational field of a planet, g
g = GM/R squared
Where, G is Gravitational constant
M is mass of the planet
R is distance of the entity from centre of the planet
3. This formula states that, larger masses have more gravity.
4. It also means that the closer the two entities are, the stronger the gravitational pull.
5. The force between Earth and you is your weight.
6. If you want to leave Earth’s gravitational force behind, an entity must travel at least 7 miles/second, which is actually our planet’s escape velocity.
7. Gravity always attracts, never repels.
8. In reality, an apple didn’t hit Newton’s head, but it made him wonder about Gravity.
9. Albert Einstein’s general theory of relativity is used as a modern description of gravity.
10. Gravitational force accelerates everything at the same rate, regardless of the weight.
What are your thoughts about Gravity? Have you anything to add to this list? Please share in comments.
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