The Effects of Zero Gravity

Author: Brianna Hang

Editors: Katelyn Ma and Liane Xu

Artist: Nicole Tseng

Isaac Newton once mentioned, “What goes up must come down...” -- but what if it never comes down? Without gravity, life on Earth would be unrecognizable, and everything would be floating into the void of space. In such an impossible scenario, researchers created facilities for astronauts to experience what it would be like to float in space. Microgravity, otherwise known as zero gravity, is a condition of weightlessness that a person or object experiences in space due to small amounts of gravity. However, there are issues concerning the health implications that could affect the living body considering the use of zero gravity facilities as a way to train the body for the space environment. In this article, we will discuss the technology behind zero gravity and the physical and mental responses of the body towards space.

Researchers study weightlessness to experiment and develop hardware technology that can be used for space shuttles and satellites. An example would be NASA’s Zero Gravity Facility, located in Brook Park, Ohio, that provides a simulation of microgravity for 5.18 seconds. Although it may not seem like it, objects that appear to be floating mid-air are free falling. According to NASA, “The free fall is conducted inside of a 467 foot (142 m) long steel vacuum chamber. The chamber is 20 ft (6.1 m) in diameter and resides inside of a 28.5 ft (8.7 m) diameter concrete-lined shaft, which extends 510 feet (155 m) below ground level.” In a vacuum chamber, air resistance and pressure are taken out as a factor, so gravity makes objects fall at the same rate. If a feather drops at the same time as the bowling ball, then the bowling ball would hit the ground first because of the air resistance pushing up against the feather. But without the resistance, they would have the same acceleration. This applies to spacecraft since everything inside it—like the astronauts and objects—is falling toward the Earth, but also orbiting at the same time. As a result, the astronauts and the spacecraft appear to be floating, and paradoxically free falling at the same time. Also, there are reduced-gravity aircraft made for training astronauts, teaching students, conducting research, and providing a background set for movies. The airplane is like a rollercoaster that moves in a parabola formation giving the people and objects on board the weightlessness feeling for 25 seconds which is much longer compared to the Zero Gravity Facility. Astronauts are required to participate in the flight to simulate a similar experience in space so they could get used to it. After that, they go through the anti-gravity treadmill that helps strengthen the muscles by strapping themselves in a harness and mimicking gravity by changing the air pressure of the inflatable machine. Overall, microgravity is continued to be studied extensively as a way to provide a safe environment for astronauts and advance the development of spacecraft suitable to launch.

On the other hand, there are health risks that need to be taken into consideration. People can experience these symptoms in microgravity:

  • Nausea

  • Disorientation

  • Headache

  • Loss of appetite

  • Congestion

  • Loss of muscle

  • Brittle bones

The nausea and disorientation can also be known as Space Adaptation Syndrome (SAS), or “space motion sickness,” where the visual area of the brain receives information that does not match with the vestibular organs in the inner ear, which detects head motion and position relative to gravity. Fortunately, the brain relies on the visual area more, and the body will get used to the position and direction in zero gravity after getting used to flying in zero gravity. Consequently, through an overexposure of zero gravity, fluids in the body would be redistributed to the upper half of the body. Most fluids in the body are gathered in the lower half of the body due to gravity and the blood circulation from the heart. However, without gravity, there is no need to provide any fluids to the lower half, and the system continues its normal functions near the head. As a result, astronauts develop puffy faces, blurry vision, loss of balance, and even loss of taste and smell. The most dangerous consequence of zero gravity would be “orthostatic intolerance” where the astronaut cannot stand for about ten minutes without assistance and he can pass out. Another major effect of microgravity is muscle atrophy (loss of muscle) and osteoporosis (brittle bones). Since there is no weight on the muscles, they begin to lose about 20% of their muscle mass within 5-11 days, so astronauts would have to regularly exercise using resistance training or the anti-gravity treadmill. According to Davidson Institute of Science Education, “Studies on mice have shown that after 16 days in zero gravity there is an increase in the number of bone destroyer cells and a decrease in the number of bone-building cells, as well as a decrease in the concentration of growth factors known for their ability to help create new bone.” Compared to Earth, there is an equal balance of bone destroyer cells and bone-building cells to create new bones. The brittle bones mostly center near the pelvis and hip joints due to the lack of mechanical movement and pressure of gravity enacting on the bones. Fortunately, astronauts can regain their normal bone density after spending about three to four years back on Earth.

Not only do scientists experiment using objects and astronauts, but they also use animals and insects to test zero gravity safety. When space exploration was considered fairly new, Russian scientists sent a dog, named Laika, into orbit around the Earth to see the effects of gravitational forces and if humans could survive up in space. The majority of the animals/insects used as a test subject would be invertebrates, butterflies, snails, and fish because some of them require special considerations such as what they will eat, where they would sleep, and how they would stay in one place. Researchers also observed fishes and tadpoles’ swimming patterns in pressurized water containers compared to on Earth because instead of swimming in a straight line, they loop around in circles without any force tying them down, as well as, respond to light as a guide. Baby mammals have a difficult time adjusting to the new environment, where they are constantly floating and drifting apart, because they depend on the warmth and touch of each other. The United States Department of Agriculture Animal Welfare Act and the Public Health Services Policy Welfare Act protect the well-being of the animals and provide ethical minimum standards for them once they get tested. Compared to humans, animals cannot give participation consent which pushes further into stricter regulations for the animal’s safety and health.

In summary, as technology is continuing to advance more rapidly than ever, researchers are discovering ways to provide safer zero-gravity environments for astronauts and animals. Through experimenting with zero gravity, there’s more we can learn about other planets besides the Earth based on gravitational forces. Although we may never experience zero gravity naturally on Earth, we can only assume disaster would be the only possible outcome. Water, air, and land would escape into the endless void, and life would never survive that catastrophe scenario.


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