# GRAVITY

**W**hen we think of gravity, we tend to think of sir Isaac Newton sitting under an apple tree; an apple falls on his head, and the idea of gravity is born. The story probably didn’t happen quite that way, but Newton did observe falling objects, and he did wonder what mysterious force drew them to the ground and why some items seemed to fall faster than others.

**N**ewton’s law of universal gravitational, published in 1687, holds that everything in the universe exerts a pull on other objects (called attraction), and the pull increases with mass and proximity.

**O**thers expanded upon Newton’s work, including Pirre-Simon LaPlace and Albert Einstein, and today gravity has helped us to build such thing as suspension bridges, elevators, escalators, and earthquake-proof buildings, By understanding the pull gravity has on the tides, we can use water to generate power.

**U**nderstanding the effect of gravity helps us hit a bulls-eye on a firing range. It explains why planets have elliptical orbits. We’ve applied our knowledge of gravity to baseball, using it to calculate the distance of home runs. because the law of gravity is universal, it applies not just to live on earth but the universal beyond.

## THE UNIVERSAL LAW OF GRAVITATION

**F**rom Newton, we understand that gravity is largely determined by mass. Think of gravity as a measure of attraction between two objects. The more mass an object has, the greater its attraction, or gravitational pull. In addition, the smaller the distance between two objects, the stronger the gravitational pull. this pulling force sucks things toward an object’s center of mass.

**T**hat’s why our spherical Earth, which is quite massive, draws objects powerfully toward its core. The pull it exerts is gravity, which keeps us from flying off into space. This law is considered universal because it’s constant, regardless of where you are in the universe. there’s gravity on earth, as there is one every other planet and celestial body.

## ELLIPTICAL ORBITS OF PLANETS

**W**hy do planets have an elliptical, instead of a circular, orbits? In a word. gravity. That the orbits of planets were elliptical (in the shape of an ellipse, or oval) was fist proposed by johannes Kepler in his three laws of planetary motion. it wasn’t until Newton developed his law of universal gravitation, though, that we understood why.

**A**n elliptical orbit is the result of a complicated tug of war between the gravitational pull of different celestial bodies, like the sun and the planets. the bigger the celestial body, the more pull it exerts on a smaller object around it. One massive body, acting alone, might create a circular orbit.

**B**ut if there’s more than one massive object, as in our solar system, each orbiting object will have an elliptical orbit. In addition, the farther away from the sun a planet is, the less it feels the sun’s gravitational pull.

**S**ome planets have a more complicated orbit than others, which was partially explained by Einstein, who later refined Newton’s explanation, adding the effect of the curvature of space-time. AN object, like the sun, has mass and this mass essentially deforms space-time, causing it to curve. The work of Kepler, Newton, and Einstein helped us to understand the complex mathematics involved in planetary orbits.

**And the orbit of the planet can change.**

**A**ll celestial bodies–Including the sun — are moving so, as the gravitational pull changes, the orbits change, becoming more or less elliptical in response to the changes in velocity and mass.

**So, friends, we hope you know everything about gravity. see you soon……………………………….**