Gravity is a force. Is that statement actually true? Isaac Newton was the first to discover gravity and described it as some force between any two bodies in the universe no matter how far apart they are. What he did not tell was what would happen if one of the bodies suddenly disappeared? What happens if the bodies are very, very small? What happens if the bodies move at very high speeds?
Albert Einstein, in his theories of relativity, explained gravity not as a force but as a fabric of "space-time". Now, what is this space-time?
See Also: Theory of Everything
What is a Space-Time?
A space-time, in simple words, is a giant fabric-like geometrical structure under any massive body in space. Gravity, on the other hand, is the curvature that is caused due to the mass of a planet or any celestial object. The heavier the object is, the more gravity it creates.
Imagine a giant net, if we place a ball in the center of it, the ball would cause a curve in the net due to its mass. The same way the planets and stars cause the curve in space-time.
Space, which is considered a physical place, and time, which we measure to calculate the duration of any observing phenomena, were considered separate but Einstein thought of them as intertwined, two inseparable necessities. If we calculate space, we automatically have to calculate time as well. Imagine you tell someone when are you meeting them, you have to tell them also where. Space and time!
What Does Gravity Have To Do With Space-Time?
Gravity, which was earlier considered as some force, has a new definition now, according to Albert Einstein. It is not only related to the mass of the body but also the time and speed at which it is traveling. The faster a body moves in space, the slower it moves in time.
See Also: How is Space-Time Uncurved Again?
Gravity is Not a Force But a Wave:
No doubt now gravity is given the title of "waves" or ripples in space-time. This huge discovery happened in the year 2015 at NASA when scientists detected gravitational waves for the very first time at Laser Interferometer Gravitational-Waves Observatory (LIGO) in collaboration with MIT and Caltech. These gravitational waves were produced by the collision between two massive black holes, 1.3 billion light years away, which means they collided 1.3 billion years ago and the waves traveled all the way to Earth in 2015 for us to observe!
LIGO Image Credit: MIT/Caltech/LIGO |
Why Is It So Hard to Detect Gravitational Waves?
Gravity, out of all the four fundamental forces of nature, is the weakest. Though even a sub-atomic particle creates gravitational waves they are so small that we cannot even think to observe them. Only some massive collisions can create gravitational waves strong enough to detect, like a star exploding into a supernova, two black holes colliding, or two binary stars orbiting each other.
Conclusion:
Gravitational waves have been detected and proven to exist but still, we are unsure about the true nature of gravity. Keen minds, dedicated souls, and hardworking individuals are required to study hard and develop some answers. If no answers, still ask questions which is the true essence of science.
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