Pushing Gravity [Englisch] [Taschenbuch]

Some of the greatest minds in history have pondered this question-and then pretty much given up on it. Newton, and later Einstein, to a more exacting degree, gave us mathematical models of gravity, which hold true to this day. Except that they say nothing about the mechanism which actually causes gravity. Einstein's theory, General Relativity (GR), attributes the cause to the "fabric of space." But as Tom Van Flandern, one of the contributors to this book, points out, Einstein's "rubber sheet analogy" presumes real gravity underneath the "fabric" which causes planets to sink down into the "gravity wells" in the sheet. It therefore explains nothing about the real cause of gravity.
In the mid 18th century, G.L. LeSage proposed a mechanical theory of gravity whereby tiny particles in space move about in all directions and at very high speeds, causing equal force on all sides of any object or planet they make contact with. But the space between any two objects has less of these particles or "gravitons" than the surrounding space, because some of the gravitons have already been absorbed as they passed through the object. This dearth of gravitons between objects causes a kind of low-pressure area allowing the gravitons in the outlying areas to push the objects together-thus causing gravity.
LeSage's theory has been revived and then rejected by many famous scientists over the years, and is presently undergoing its most recent revival. If such particles exist, there must be a way to detect them. One method, attempted by the physicist Q. Majorana, early in the 20th century, was to test the effect that gravitational shielding has on the absorption of gravitons and hence the weight of objects. Through elaborate scaling experiments carried out in a very careful and meticulous manner, he obtained some seemingly positive results. But these results, along with more recent shielding experiments using satellites in Earth orbit, have not been conclusive. They have not yet been demonstrated to the satisfaction of the mainstream of science.
What the theory of pushing gravity does have, especially in its modern versions, is its compelling logic. It posits a physical cause to gravity as opposed to, for example, Newton's instant action at a distance, (IAAD), (which, incidentally Newton was never happy with), and Einstein's "fabric of space."
Van Flandern, an astronomer, and one of pushing gravity's most convincing advocates, points out that IAAD can be better explained by positing gravitons which move at many times the speed of light. A slower propagation speed, e.g., the speed of light, would cause a delay or aberration of the signal carrying the gravitational force between, say, the Sun and the Earth. This would cause Earth's orbit to be unstable.
For those interested in serious cutting edge science, but accessible to the intelligent layman, this is a fascinating book. There is some "quantitative" (i.e. mathematical) description, but most of the essays are perfectly lucid on the "qualitative" (verbal) level.
If there is ever to be "anti-gravity" science in mankind's future, the physical cause of gravity must first be understood. This book is a must for optimistic science enthusiasts.

This is a remarkable book, from both the historical side of science and

from the future side, as well. The book shows that, contrary to what is said

for the laity, gravity is still not understood, and perhaps Einstein wasn't correct

in everything. There is an amazing, short chapter uniting gravity and EM theory

by suggesting that gravity is just ultra-long EM waves! And they are ultralong

because of the Compton effect. The Compton effect puzzled Bohr and Einstein,

and ultimately convinced Bohr about quanta. That it might be the cause

of gravity is an exciting idea. The book deserves reading my anyone adventarous

enough to think that scientific ideas should be considered that aren't in the

beaten path.

This is an eminently refreshing book. In a world that takes "bending of space" as literal, and for granted, it's worthwhile remembering that we still don't have a mechanism for how gravity works. Even the "bending of space" might imply being "pushed" by interaction with particles from some physical fourth dimension.

This book takes a step back from that and tries to posit physical underpinnings of gravity in our own universe, no extra dimensions required.

The major underlying position of the papers in this book is that gravity is caused by the pushing force of particles. That said, there's an impressive variety of mechanisms through which it can be accomplished, and various authors set out to posit their particular solutions.

Explanations range from the markedly hypothetical (Tom van Flandern posits faster-than-light interaction, disallowed by Einsteinian relativity, but surprisingly allowed by Lorentzian relativity), to the almost 'banal' (positing that gravity is caused by normal EM particles of a particular wavelength, along the same way that microwaves and heat-infrared interact), and many options in-between.

There's a lot of solid mathematics going on here, which you can follow along with, and a lot of decent prose to go with it.

What I found most interesting was that, while many equations duplicate the inverse square law to the umpteenth degree, many of the theories posit testable aberrations from the inverse square law. That may be the lynchpin to their success (or failure). Some propose they might solve the mysteries of the aberrations of satellite orbits, or even why a galaxy can maintain its outer rim shape without huge amounts of dark matter.

Highly recommended.