Gravity is invisible, and it’s everywhere.Materials with different densities on Earth’s surface and in its interior influence Earth’s gravitational pull-mountains actually pull plumb bobs toward them because of their large mass compared to the air around them. Synopsis: Earth’s gravity is everywhere, and everything with mass exerts gravitational pull on everything else. We’ll explore the surprising things that changing gravity reveals on a future EarthDate.
It’s the different densities of different places on Earth that cause Earth’s gravity to vary. Mountain ranges in general have stronger gravitational pull than, say, oceans, since rock is denser than water. Not enough for you to notice, but measurable with a sensitive instrument. If you’re standing next to a mountain and holding a lead weight on a string, that weight would not hang perfectly straight but would be drawn slightly toward the mountain. If Earth had a smooth surface, and were the same density in all places, gravity would be the same everywhere. The moon has less than Earth-and thus orbits around us-but still has enough gravity to pull on Earth’s water, causing tides. The sun has more gravitational pull than Earth, which holds Earth in orbit around it. The strength of this pull is determined by the object’s size and density. In fact, Earth as we know it couldn’t exist without gravity.Īll objects exert a gravitational pull on other objects. But it keeps us standing upright, keeps water in our glasses and in the oceans. Working against it keeps our muscles toned, and the rest of us…not so toned. That is, until we turn 50 and we’re confronted with the evidence. There’s one Earth system that constantly affects our lives, yet we hardly think about it. Areas with more mass are red, and areas with less mass are dark blue. Gravity-anomaly maps of the Earth’s geoid show how Earth’s actual gravity field differs from the gravity field of a uniform, featureless Earth surface.
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