In 1687, Sir Isaac Newton publishes his theory on Gravity. It says that it a force that attracts any two objects having mass and some distance between them. This explained why everything falls on the ground, why the earth orbits the sun, why the moon orbits the earth. Gravity as a force was accepted generally for some centuries as this theory can be applied to all objects. Indeed it was Sir Isaac Newton who described the effects of gravity, but Albert Einstein was the one to explain how it truly works.
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| Sun and Earth Distorting Space-Time |
Albert Einstein predicted through his general theory of relativity that gravity is distortion in the fabric of space-time rather than being a force. Space-time is a concept where the 3-dimensions of space is combined with an additional dimension of time making it 4-dimensional. It explains that the heavier is an object the more it distorts the space-time similarly to an object placed on a stretched out fabric. If any other object is introduced in its vicinity then the objects tend to attract each other. Also, this explains why light bends around denser objects. Even though light wants to travel in a straight line, it bends in the presence of a distorted space-time. Gravitational lensing is also a product of this phenomenon where a very dense object distorts the light coming from any other object behind it and it seems to produce multiple images around the dense object.
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| Gravitational Lensing |
While Einstein's theory of space-time might look absurd, we have already confirmed this theory in 2016. It took us more than a century to confirm his theory which says a lot of his genius mind that was able to come up with a theory like this. When two very heavy objects revolve each other like black holes or neutron stars with tremendous speed or when a supernova occurs, the fabric of space-time distorts in such a manner it looks similar to ripples in water when you drop something in it. These ripples in space-time are called Gravitational waves and they travel at the speed of light which means that if any big enough event to create these ripples will take the exact same time to reach the earth as the light from the same event would reach us. LIGO labs which are primarily established to detect these waves detected them in 2015. Supposedly it was caused by a merger of two black holes about 1.4 billion years ago.
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| Gravitational waves |
Even though Einstein's theory is proved, for most purposes, gravity is considered as a force as it is simple for many calculations.
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