Physicists are searching for the particle responsible for the gravitational force.
One is gravity. Gravity is the force by which a planet or other body draws objects toward its center. The force of gravity keeps all of the planets in orbit around the sun. Gravity: an invisible force that pulls objects toward each other. Earth’s gravity is what keeps you on the ground and what makes things fall. Anything that has mass also has gravity. Objects with more mass have more gravity. Gravity also gets weaker with distance. So, the closer objects are to each other, the stronger their gravitational pull is.
Earth’s gravity comes from all its mass. All its mass makes a combined gravitational pull on all the mass in your body. That’s what gives you weight. And if you were on a planet with less mass than Earth, you would weigh less than you do here.
Yet, gravity is one of the most mysterious forces in the Universe. gravity remains on many levels fundamentally mysterious. Why is it so weak compared with the other forces? Why does it only pull, not push? And why is the strength of “Big G” (whose value is, incidentally, notoriously difficult to pin down) so apparently finely tuned to allow life to emerge? If it were just a little less, the expansion of space would have overwhelmed the pull of gravity on the matter in the newborn universe, stars and galaxies would never have formed. If it were just a little more, any wannabe stars or galaxies would quickly have collapsed in on themselves and each other, while space-time would have folded up the whole universe in a big crunch. We have a lot to thank for gravity being like it is.
As physicists are searching for the particle responsible for the gravitational force, there is hope to find the graviton. So why hasn’t anyone found a graviton yet? The problem with searching for gravitons is that gravity is incredibly weak. Individual gravitons are thought to be massless and interact very feebly, and we are only held to the planet because the Earth emits so many of them. Because a single graviton is so weak, it is impossible for us to directly detect individual classical gravitons. So, in the end, while the effects of gravity are easily seen, at this time it remains a mystery.
NASA Science
We are all Interconnected even with the Universe 
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