Gravity seems to be a very basic and down-to-earth subject. We learn from birth the dictates of the “Law of Gravity.”

The Earth without fail pulls everything to itself. We simply take it for granted. Indeed, the Newtonian Law of Universal Gravitation explains the orbits of the planets, the trajectory of a projectile and our first fall off a bike equally well.

In basic language, the Newtonian Law says that any two masses attract each other with a force that is 1) proportional to the product of the two masses and 2) inversely proportional to the square of the distance between the two masses.

In other words, “big mass, big gravity” and “farther away, less gravity.” Many very useful and significant calculations can and have been made using these two basic concepts.

However, if we just ask two simple questions about gravity, things get pretty mysterious and almost unbelievable. The questions are:

1) Can anything stop or shield gravity?

2) How do any two masses even know the other mass is there (i.e., how do they communicate)?

Gravity cannot be shielded. Gravity acts between two masses regardless of what is between them. Every other force I know of can be shielded, canceled or neutralized in some way.

The force of gravity that holds the earth in orbit around the sun goes right through the earth unaffected, as if the earth was not even there.

The only thing that can modify gravity is gravity. The three-part gravitational dance between the Earth, Sun and Moon is an example of gravity affecting gravity here in our corner of the universe.

As to how masses communicate gravity, I know of nothing like a gravity beam or wave that has been confirmed that goes from one mass to the other to communicate gravity. The only thing close to this would be the notion of a “gravitational field” surrounding a mass; however, this field is only known by its effects.

Nevertheless this as-yet undiscovered method of communication of gravity between two masses is very precise.

We have all heard of the story of Galileo dropping two objects of different weight simultaneously from the Leaning Tower of Pizza and finding they both hit the ground at the same time.

We all know intuitively that it takes more force to accelerate a large weight versus a smaller weight.

So you tell me how the dumb Earth and the different objects communicate to size the gravitational force on each object perfectly so that different weight objects accelerate toward the earth at exactly the same rate.

It seems more reasonable to me that the gravitational force would be constant and the resulting acceleration of each object different. But no, gravity sizes the force precisely for each object to get the same acceleration — wow.

So, it would seem that gravity is a force that acts precisely everywhere with no obvious connecting medium.

Seems to me from a purely logical point of view, it is almost as easy to believe in a spiritual force as it is to believe in a gravitational force.

Both are:

  • Significant forces;
  • Have no obvious connecting medium;
  • Cannot be shielded or stopped;
  • Known only from their effects; and
  • Seem to have inscrutable methods of communication.

Joe Concienne of Galveston, a chemical engineer who spent much of his career in Texas City, writes an occasional column on the basic concepts of science. He can be reached at concien@aol.com.

(6) comments

Johann Ramirez

Thank you! This was a very enjoyable read.

Mike Leahy

Joe: could you please explain the difference between Atmospheric Pressure and Gravity? Thanks.

Joe Concienne

micealo'laochdha: I wrote a column on Atmospheric Pressure. It was published in The Daily News on April 8, 2014 page B4. See if that helps.
In short Atmos. pressure is the weight, at the earth's surface, of the air which makes up our Atmosphere. The Air is held in place around the earth by Gravity. The air is energetic enough, manily due to sunlight, to keep from all collecting right at the earth's surface. Hope this helps

George Croix

You want to have some fun with gravity, go with it's effect on a fired bullet, as you make every effort to explain the difference between drop from line of bore, and drop from line of sight, to a few folks, otherwise smart as heck, conditioned since birth to believe that the bullet rises on it's own.
[wink]

David Dearman

I love reading about science in the GCDN and discussing with friends and family. My son who is an aerospace engineer suggested that the description of gravity here rather appears to ignore Einstein's general relativity. Gravity is not a force but a curvature of space-time. It acts like a field and changes are propagated by waves that travel the speed of light. To me it's not so much the unknowns of science that point to the spiritual as much as it is the mathematical beauty of what we do know...the stamp of the creator on creation, so to speak.

Joe Concienne

Ddearman01 Thanks for comment. I debated whether to mention general relativity and spacetime curvature. I had it in my first draft. However I decided it complicated the article and it did not change my conclusions. So I decided to leave it out because in the end it did not change my conclusions.
There has not been any physical confirmation ,to my knowledge , of a gravity wave or particle. Exactly how gravity is communicated , to the best of my knowledge, is still in the realm of good theory not experimentally proven fact. Please respond if you or your son does not agree. Thanks again for commenting.

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