"The effect of gravity on astronauts"

 

What is gravity?

Gravity is one of the four fundamental forces in the universe, alongside electromagnetism and the strong and weak nuclear forces. Despite being all-pervasive and important for keeping our feet from flying off the Earth, gravity remains, in large part, a puzzle to scientists. Ancient scholars trying to describe the world came up with their own explanations for why things fall toward the ground. The Greek philosopher Aristotle maintained that objects have a natural tendency to move toward the center of the universe, which he believed to be the middle of the Earth, according to physicist Richard Fitzpatrick from the University of Texas. But later luminaries dislodged our planet from its primary position in the cosmos. The Polish polymath Nicolas Copernicus realized that the paths of the planets in the sky make much more sense if the sun is the center of the solar system. The British mathematician and physicist Isaac Newton extended Copernicus’ insights and reasoned that, as the sun tugs on the planets, all objects exert a force of attraction on one another. 

Effects of gravity on in astronauts:

 The sensation of weightlessness, or zero gravity, happens when the effects of gravity are not felt. Technically speaking, gravity does exist everywhere in the universe because it is defined as the force that attracts two bodies to each other. But astronauts in space usually do not feel its effects.

The International Space Station, for example, is in perpetual freefall above the Earth. Its forward motion, however, just about equals the speed of its "fall" toward the planet. This means that the astronauts inside are not pulled in any particular direction. So, they float.

Not having to bear weight on your feet sounds relaxing, but in the long term there are many health problems associated with it. Bones and muscles weaken, and other changes also take place within the body. One of the functions of the ISS is to study how astronaut health is affected by long periods in weightlessness. 

Experiencing weightlessness

You don't have to leave Earth to (briefly) escape the bonds of gravity. Anyone who crested the top of the hill in a fast roller coaster, or who sat in a small plane pushed down suddenly by the wind, briefly experienced weightlessness.  More Sustained periods are possible in planes that fly a parabola. NASA’s reduced gravity flight program, for example, flies planes in a series of about 30 to 40 parabolas for researchers to conduct experiments on board. Each climb produces a force about twice the force of gravity for 30 seconds. Then, when the plane, also called the “Vomit Comet” because it makes some passengers nauseous, reaches the top of the parabola and descends, passengers feel microgravity for about 25 seconds.