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Gravity: You don't know what you've got 'til it's goneHere on Earth, we take gravity so for granted that it took an apple falling from a tree to trigger Isaac Newton's theory of gravitation. But gravity, which draws objects together in proportion to their mass, is about much more than fallen fruit. Read on for some of the strangest facts about this universal force.
It's all in your headSlide 2 of 13
It's all in your head
Gravity may be pretty consistent on Earth, but our perception of it isn't. According to research published in April 2011 in the journal PLoS ONE, people are better at judging how objects fall when they're sitting upright versus lying on their sides.
The finding means that our perception of gravity may be less based on visual cues of gravity's real direction and more rooted in the orientation of the body. The findings may lead to new strategies to help astronauts deal with microgravity in space.Slide 3 of 13
Coming down to Earth is toughSlide 4 of 13
Coming down to Earth is tough
Speaking of astronauts, their experience has shown that a switch to weightlessness and back can be tough on the body. In the absence of gravity, muscles atrophy and bones likewise lose bone mass. According to NASA, astronauts can lose 1 percent of their bone mass per month in space.
When astronauts come back to Earth, their bodies and minds need time to recover. Blood pressure, which has equalized throughout the body in space, has to return to an Earthly pattern in which the heart must work hard to keep the brain nourished with blood. Occasionally, astronauts struggle with that adjustment. In 2006, astronaut Heidemarie Stefanyshyn-Piper collapsed at a welcome-home ceremony the day after returning from a Space Shuttle mission to the International Space Station.
The mental readjustment can be just as tricky. In 1973, Skylab 2 astronaut Jack Lousma told Time magazine that he'd accidentally smashed a bottle of aftershave in his first days back from a month-long sojourn in space. He'd let go of the bottle in mid-air, forgetting that it would crash to the ground rather than just float there.Slide 5 of 13
For weight loss, try PlutoSlide 6 of 13
For weight loss, try Pluto
Pluto may no longer be a planet, but it's still a good bet for lightening up. A 150-pound (68 kilogram) person would weigh no more than 10 pounds (4.5 kg) on the dwarf planet. The planet with the most crushing gravity, on the other hand, is Jupiter, where the same person would weigh more than 354 pounds (160.5 kg).
The planet humans are most likely to visit, Mars, would also leave explorers feeling light-footed. Mars' gravitational pull is only 38 percent that of Earth's, meaning a 150-pound person would feel like they weigh about 57 pounds (26 kg).Slide 7 of 13
Gravity is lumpySlide 8 of 13