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
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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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Gravity
by D. R. Prescott



Few things affect us more than gravity. Surprisingly, very few people know much about it, other than it holds them down to the ground. All material objects possess gravity-our Earth, the moon, the sun, galaxies, you, me, atoms, subatomic particles… everything!

Some people even think that you can get away from gravity in orbit because you feel weightless. In orbit, you are constantly falling in this force’s clutches around a center of gravity, producing that often queasy, weightless feeling. What you weigh is caused by gravity and the resistance of the Earth’s surface to your tendency to fall toward its center, or, alternatively, to be pulled by gravitons from the mass below (and here you thought it was what you eat!)

You could lose a bunch of weight just by living on the moon; a one hundred thirty-pound human would weigh about 22 pounds on the moon. Weight is an effect of gravity, which you can control by where you are at the moment--travel and lose weight, not a bad deal. Mass, volume and density are the real problems for our hypothetical weight-loser. This is a good time to clarify a few of important terms. Mass is how much material. Volume is how big. Density is how tightly packed (Remember that old Camel’s cigarette slogan, “So round, so firm, so fully packed?” Guess not, unless you were around in the 1950’s and 60’s.) So, you may weigh only 22 pounds on the Moon, but your body will still have the same mass, volume and density. So, your shape on Earth is still your shape on the moon-good or bad! Sorry about that, travel does not substitute for diet and exercise.

Kepler, Galileo, and Newton, among others, grappled with the idea of gravity. In his book, Principia, Newton developed three laws of motion integrating and advancing the thoughts of many before him. These laws are:

1. A body tends to keep moving in a straight line and a stationary body tends to stay put unless it is compelled to change because of some force, also known as the Law of Inertia.
2. A force, acting on a body, will change the momentum of the body in the direction of the applied force.
3. For every action, there is an equal and opposite reaction
.
These laws of motion and Newton’s law of gravitation (F=Gm1m2/d2) set the stage for modern physics. Thus, Newton went down in history as the Father of Classical Physics, not to mention that he and others invented and expanded calculus along the way. Until the 20th century, things were just fine. People went along calculating the motion of heavenly bodies with great precision, impressing generations of the uninitiated. Everything seemed to follow Newton’s laws. Everyone was happy… almost. Then, at the turn of the last century, a new sheriff came to town, stepping out of a patent shop onto science’s frontier streets with mental guns blazing. Our little, predetermined town was never the same again.

Here’s where the question of gravity gets dicey. Dr. Einstein thought his way through the work of others, added just a dose of insight, sprinkled in a little genius and concluded, through some significant mathematics, that matter distorts space-time, creating the effect of gravity. The effect of Einstein’s work made Newton’s equations, at best, an approximation, although a very good approximation in practice. Strange things happen, or are more noticeable, the faster you go--mass increases, lengths shorten and time slows. Dr. Einstein outdrew nature, placed his smoking gun in its holster and walked into the sunset giving humanity a different way of looking at space, time and gravity.

Newton’s Second Law says that force is equal to mass times acceleration. Little did Newton realize that in a little over 200 years, gravity would be defined as a warp in space-time, or, more specifically, oscillations in space-time as a result of changes in the distribution of matter. It means that what you weigh here on Earth is because the Earth has sufficient mass to warp space-time. You are always trying to fall toward the planet’s center. Could it be that simple? There is experimental evidence supporting it--like light from a distant star bending its path as it passes our massive Sun.

When one talks about quantum gravity, however, a thing called gravitons enter stage right. At the subatomic level, scientists believe that certain particles or light quanta act as conveyors of forces. There are four basic forces in the universe as far as we know at the moment. They are the Strong Nuclear Force, Weak Nuclear Force, Electromagnetic Force and Gravitational Force. Each has been associated with a carrier particle. The following table shows their individual characteristics, as discussed in “The Universe that Discovered Itself”, by John D. Barrow, and reproduced below.

Chart for Gravity Article


You might notice that gravitation is weak but affects everything! While its range is infinite, gravity seems unusual, affecting everything including the other three, significantly stronger forces. This is where we must ask a question, “Are gravitons necessary?” The strong, weak and electromagnetic forces have had compelling evidence for their carrier particles. To date, I know of no one who has trapped, studied or fiddled with an actual graviton, or, even measured a gravitational wave successfully. I do know that people are working feverishly on the problem right now.

Einstein portrayed gravity as a basic effect of matter. Matter distorts space, making objects want to fall toward each other. So if gravity distorts space, the amount of which is based on its mass, every atom in our bodies must exert its contribution to the sum of our body’s ability to make things want to fall toward us. So, we are naturally attractive creatures!

Gravity lessens with distance, in concert with the inverse-square law. So, the farther away two objects are from each other, one object attracts the other with the less force . (If you double the distance between to objects, gravity between the two objects is lessened by a factor of 4 or 2 squared; triple the distance and it is less by 3 squared or 9 times.) If two objects are an infinite distance apart (assuming there are only two material objects in the entire universe), does space distort ever so slightly between them making one attract the other from such an inconceivable distance?

Does one know the other exists in a finite time? Would they, ultimately, in an infinite amount of time, fall toward each other from an infinite distance, orbiting each other until they bump together? From what I understand, the answer is probably yes, given an infinite amount of time. So, who needs gravitons when geometry can do the same job? All you have to do is distort space-time a bit and geometry takes over. Of course, who has an infinite amount of time to find out?

Another interesting question… How fast does this distortion of space-time occur? If the effect of gravity happens at no more than the speed of light and by some happenstance our sun suddenly acquired more mass, our Earth’s orbit would be affected to some degree eight minutes later-no faster. Does that also mean gravitons are conveyors gravitational forces at the speed of light? Would they be classical, zero-mass particles, similar to a photon? Or, is it some sort of strange quantum effect, providing a vehicle for collapsing gravity’s wave function, making the force between our two distant objects real and geometrically connected through the disturbing concept of quantum tunneling? Is quantum tunneling a part of gravity’s character, making it possible to transfer geometric information instantaneously between two objects, like the spin of separated subatomic particles? The idea of transferring information instantly from one place to another distressed Einstein a lot. It broke his universal speed limit!

The question still remains whether gravity is transferred by particles, by oscillations of space-time or both. Let’s look at the problem from another angle. Picture the Earth. You dig a hole through the center to the other side. This is a thought experiment that Dr. Stephen Eastmond and I discussed one day at Tessmann Planetarium while fixing our antiquated projector. He used this imagery once in response to a young lad’s inquisitive nature. It goes something like this.

You jump into the hole and begin falling toward the Earth’s center. You accelerate to about 5 miles per second by the time you reach the center of the Earth, some 42 minutes later as calculated by Martin Gardner in his book, “Puzzling Questions About the Solar System.” You continue on with decreasing acceleration toward the other side of the Earth, hesitating momentarily, as you come to a full, very brief stop, and wave to astonished observers. Of course, gravity is tenacious and somewhere around the edge of the hole you stop going up and begin falling back toward the Earth’s center. You will do that, passing back and forth through the center of the Earth, less and less each time because of other external forces including friction, until you finally come to rest at the center of the Earth.

If you could come to absolute rest at the center of the Earth, how much would you weigh? You’re at the bottom of the gravity well where all falling stops, at least a single point of you. There is no place to fall from the center of Earth’s mass. However, your head and feet might try to fall toward each other ever so slightly prompted by your atoms’ meager attraction.

At the center of the Earth, all Earth’s mass surrounds you, not below you pulling you down, or letting you fall into it. Whether gravity is a distortion of space caused by mass or transferred by gravitons, would not the planet’s mass tend to also try to make you fall up, or pull you up by all those gravitons tugging from above, until some equilibrium is reached? Of course, this picture neglects other factors, but that’s a danger with simplifications. It is likely taking an idea too far and missing an important point or two-such as everything above you is still tending to fall toward the center, canceling out upward forces, likely crushing you out of existence. At which point, you really wouldn’t care about how much you weigh.

So it goes with gravity. It is one of those things we know a lot about, to many decimal places. It currently separates classical physics and quantum physics. The other three fundamental forces (Strong Nuclear, Weak Nuclear, and Electromagnetism) seem to play a different role than gravity. Gravity has geometric significance to everything, all space-time. Then, you have M-theory (string theory) people suggesting that other dimensions, maybe six or seven or more, may explain universal expansion and gravitational shortcuts. Is gravity leaking out of our four-dimensional universe into spooky places we can’t see? This is the stuff from which leading-edge physicists hope to find a theory of everything (with science fiction writers struggling to keep up with them.)

We are touched by gravity every day and from every direction. In spite of its pervasiveness and our efforts to unravel its secrets, what gravity really is still eludes us. Yet, it is a rather attractive subject, don’t you think?

© 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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