About The Author
D. R. Prescott has written a novel, a collection of short stories, a nonfiction book, a collection of essays, planetarium show/display scripts, two family histories, technical articles and business plans as well as written for and edited several newsletters.
 
Awards and published work include Writers' Journal, Long Story Short, Taj Mahal Review literary journal, The Orange County Register, Writer's Digest, and Writing.com and four books among other challenges.
 
As a former aerospace executive and planetarium program director, Prescott currently writes and explores life in Orange, California.
 
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"Sentience can be annoying."-DRP Abt. 1990
*Thumbsup*
 
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Since 2008, Prescott has been a regular contributor of
essays and short stories to
The Taj Mahal Review Literary Journal
Get your copies now at: http://tajmahalreview.com/
 
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O R D E R   T O D A Y !
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Is Gravity Important?
by D. R. Prescott



Living off our wonderful planet is a vision of many. There are numerous reasons why humans should do it as I discussed in my book, IS THERE TIME? It is not only our next frontier but likely humanity’s path to avoiding extinction. There are many psychological, physiological and technological issues to confront before humans can permanently live on another planet like Mars, or anywhere else in our Solar System except Earth. One of the more critical physiological issues is gravity.

Many watch Star Trek, Star Wars and the like and probably never notice that no matter where the characters are in a spacecraft, they seem to walk normally. They don’t generally float; they don’t seem unusually lighter on their feet; nor do they seem stressed by more than normal gravity. The exception is when they don spacesuits and float in open space or wear magnetic-shoes to hold them to the exterior of the vessel. However, back inside their ships, Earth-normal gravity magically returns. Some of you may ignore the problem by assuming that unexplained technologies of the future (or, in the case of Star Wars, “long, long ago”) take care of that problem; but, to appreciate the problem, it is necessary to consider just what it takes (with what we know today) to produce gravity.

The first way to produce gravity is to have mass. All mass has what I’ll call “natural” gravity. If you get enough mass together in one place, the effects can be quite noticeable, for example, our planet. On Earth’s surface, we have all the mass of the planet beneath us. The mass in your body and the Earth’s mass are attracted to each other. If you weigh 150 pounds with the mass in your body (the amount of material), it is because you are falling toward the Earth’s center at 9.8 meters/second2 but the surface of the planet is stopping you; hence, your downward pressure versus the Earth’s surface resistance is your weight.

When you are in orbit, you weigh nothing because you are not pressing against anything; you and your ship are in freefall around the planet but still have the same mass as you did on the ground. Your craft and you are moving at the same speed, so you feel no weight. Weight and mass are two different things. Weight is a measure of your mass being accelerated at some speed which the mass you are standing or sitting on is resisting letting you fall to its center. Mass, on the other hand, is how much material is packed into your body or a planet. So, in orbit you have the same mass as on Earth, just no weight.

Acceleration is the second way to produce the effect of gravity. If you are in a spaceship accelerating at 9.8 meters/second2, you would weigh exactly what you weigh on Earth. The same thing can be done by revolving your mass about a central point like on those carnival rides (sometimes called the Roundup or Rotor.) This ride is a circular platform with a vertical cage-like wall with room for about thirty people standing with their backs to the cage wall. At first the ride rotates horizontally until it is up to speed pressing the riders to the cage wall at about 4 gravities. Gradually, the whole rotating platform inclines to about 50 degrees from level and nobody falls out because of the simulated gravity overpowering Earth’s downward pull. Pilots and astronauts use similar things called centrifuges to train for high-g situations. So, on the carnival ride, you “weigh” four times what you normally weigh because of acceleration with no change in your mass. In a space station, it is possible to simulate near Earth normal gravity as was wonderfully demonstrated in a sequence of the 1969 Arthur C. Clark movie, 2001, A Space Odyssey.

When you are in a car that suddenly accelerates, you are pushed back in your seat because your mass has been accelerated in a straight line instead of in a circle like on the carnival ride. You feel the acceleration as weight until the car stops accelerating and your body and the car begin traveling at the same speed. You don’t feel weightless because the Earth’s gravity is still holding you in your seat.

Weightlessness that astronauts experience in orbit is not the absence of gravity; it is because their orbital speed is fast enough that their vehicle freefalls about the planet where Earth’s gravity is balanced by the ship’s speed. If the astronaut fires a rocket and speeds up his spacecraft, he will feel some weight toward the opposite direction of acceleration and will move farther away from the Earth. If he fires a rocket in the direction of travel, he will experience some weight in the opposite direction and decrease his orbit or perhaps fall back to Earth.

With that explanation of “natural” and artificial gravity, let’s use the Moon and Mars as common examples of where some people think humans should live. Mars is becoming more attractive since our space probes have verified that water is locked up in its frozen surface. Water is a key ingredient for sustaining life as we know it. Food is another primary requirement. Air to breathe would be real handy too. Often, these discussions of colonizing other worlds leave out any serious discussion about gravity and humans need for it.

All of us were born into a world where 9.8 meters/second2 is normal acceleration due to gravity. Our bodies are tuned for it, of course, some better than others. When we leave Earth-normal gravity, things start happening to our bodies and not necessarily good things. On Mars, a 150 pound person would weigh about 50 pounds. On the Moon, that same person would weigh 25 pounds. That may sound great. Think of all the superhuman things you might do in such an environment.

Don’t pack your bags yet unless it is only a vacation. Lack of Earth-normal gravity upon the human body needs a lot more study. In an Associated Press article in August 2010, Marcia Dunn, AP Aerospace Writer, reported, “Astronauts can become as weak as 80-year-olds after six months at the International Space Station…” Negative changes in astronauts’ muscles were revealed down to the “cellular level.” There are likely ways to overcome these changes with rigorous exercise regimes on the proper equipment. But, how many permanent Martian colonists will follow such demanding therapy to avoid muscle atrophy? How many people exercise here on Earth? I suspect that there will be little difference in permanent Martian habits once they settle into life on Mars. People will be people. The “path of least resistance” will eventually prevail and forced exercise will wane.

We don’t know enough yet about the affects of living in reduced gravity whether it is one-third or one-sixth that of Earth. What is known from studies of astronauts in space over the last 50 years is things happen to the human body in prolonged weightlessness such as:

• Body fluids tend toward the head making the brain think that it needs to 
get rid of fluid which threatens dehydration.
• Muscles get weaker and shrink.
• Weight-bearing bones tend to dissolve.
• Cardiovascular changes occur.
• Reduction in red blood cells has been observed.
• And, a host of other disturbing anomalies from changes in stature and
posture to increased flatulence.


Many of these negatives may be minimized if the human body returns to a one-g environment periodically. But reduced gravity may present serious issues like weightlessness. A colonist planning to leave Earth to live on the Moon or Mars may, given enough time, be purchasing a one way ticket. Even a brief vacation home to Earth after living for years in one-third or one-sixth gravity might be a grueling task. Suddenly being exposed to full Earth-normal may be debilitating or even lethal without intense preparation beforehand.

The human body is a one-g mechanism; it functions strangely when weight is removed; how much it will be affected in lower than one-g is up for grabs, particularly for future generations of colonists who have never lived in anything but one-third or one-sixth gravity. Is this the next evolutionary step where new subspecies of Homo sapiens will emerge adapted to their reduced gravity environments? Will they be taller and weaker than their Earth relatives? Will they be more graceful or beautiful or, maybe, ugly? Will that be good or bad?

There is only one way with current science and technology to overcome the reduced gravity issues to keep spacefarers Earth-normal—build artificial habitats with one-g environments that create the effect of weight through rotation. Such ideas have been bandied about for decades. Orbiting colonies have been suggested housing as many as 10,000 people to nearly a million people. Much more needs to be done, particularly if the human race plans to grow and continue improving human life. The technological challenges are great but our species is noted for coming up to the task.

In my piece published in the Taj Mahal Review titled, TOO MANY PEOPLE, I demonstrate that in a relatively short time, humanity will need more space than is available on Earth if we are to grow and prosper. We will likely run out of space to live (exceeding Earth’s carrying capacity) in just a couple of centuries and that is assuming a dramatically lower population growth rate than we have experienced in the last hundred years. If you add up the surface area of Mars and every other known solid object in our Solar System over 200 kilometers in diameter (disregarding livability and terra-forming issues), our Solar System does not have enough surface area to house humanity in less than two to three hundred years, projected at half the population growth rate estimated by the U.S. Census Bureau for 2050. Ironically, there seems to be little or no public awareness or sense of urgency.

While taken for granted, gravity is critical for our welfare. Living in gravity produced by rotating spaceships or habitats (artificial gravity, if you like) has been studied. Designing large scale habitats require a lot of science and engineering mixed in with considerable trial and error. We humans are complex organisms requiring Earth-like environments to attend to our psychological and physiological needs. Building carnival rides where you experience artificial gravity for a few moments is one thing; it is quite another to build habitats with little or no negative long term psychological or physiological drawbacks. Future colonists must feel at home 24/7 wherever they live. If other surfaces in our Solar System can’t fulfill our requirements, then we need to accept the challenge and build places that do.

Gravity is important!





© Copyright 2010 D. R. Prescott (donprescott at Writing.Com). All rights reserved.
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' Copyright 2008 D. R. Prescott (UN: donprescott at Writing.Com). All rights reserved. D. R. Prescott has granted Writing.Com, its affiliates and syndicates non-exclusive rights to display this work. Questions or Comments? E-mail to prescottdc@sbcglobal.net
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