Zero Gravity
Written by Tega Jessa
If you have heard of the term "zero gravity," you have most likely thought that it meant that it is a environment with no gravity. The most well known example known is the pictures of astronauts floating in the space shuttle as it orbits the Earth. However, this very example proves that zero gravity as we know it, is a myth.
First the gravity of a planet extends pretty far. It's said that the full force of the Earth's gravity is still present up 100 km above the surface of the Earth. If you have read the article about elliptical orbits you would also know that the far reaching effect of gravity is what makes the orbits of planets ovoid instead of a perfect circular. This is because the planets are under the gravitational influence of both the sun and other planets. So gravity is not a force you can easily escape from.
So if this is true, why can the astronauts float in space? This is due to the phenomenon that zero gravity actually describes called weightlessness. Weightlessness can occur only two ways. First is the one we assume happens when an object is completely outside the influence of gravity. This can only happen in an area of space with no cosmic bodies around. A likely candidate would be between galaxies and even that is doubtful. The second scenario is actually what happens it is when an objects is in free fall. This means it falls solely under the influence of gravity. Without the resistance of some kind like a stationary force, you lack the feeling of weight on your body. The best explanation is Einstein's falling elevator model. If you fall at the same speed as a falling elevator you would experience free fall or weightlessness. This can occur in two ways near the Earth. One, is to be on an space craft with zero difference between its acceleration and yours. This is what makes astronauts weightless especially since there is no air resistance in space. The other scenario involves a regular airplane flying in a controlled parabola.
Weightless, while fun, has serious consequences for an astronaut. The human body was made to function under gravity. From our muscles and skeleton to our blood, all use gravity to work. Extended time in space leads to atrophy of these systems. Fortunately, regular exercise can counteract the worst of these effects during a flight. However there are some effects that can't be avoided. Some people who go to space suffer a form of motion sickness called Space Adaptation Syndrome. Since the body's balancing system also use gravity the lack of it for a period causes nausea and other discomforts. Fortunately it only last for at most three days.
If you enjoyed this article there are others on Universe Today that you will also like. There is an interesting Article about NASA testing out a method of combating weightlessness in space. There is also an interesting article about a couple saying their wedding vows in zero gravity.
There also great resources about zero gravity elsewhere on the web. There is a great article on the Howstuffworks site about weightlessness and a company that allowing the general public to experience it. There is also a great video on weightlessness and its effects on the same site.
You can also listen to Astronomy Cast. Episode 102 Gravity is a great episode if you want to learn more about gravity and its effects.
Filed under: Astronomy
