Web site: http://users.aber.ac.uk/cat/
Available from the Apeiron website at http://redshift.vif.com or
Roy Keys by mail at 4405 St-Dominique, Montreal, Quebec, H2W 2B2 Canada
(or by e-mail at apeiron@vif.com).
Note: The preface is now online at http://redshift.vif.com/BookBlurbs/PushingGravity.htm.
A fascinating collection of papers, put together very professionally, covers theories of gravity related to that of Georges-Louis Le Sage (1724-1803), from its roots (possibly due to Nicolas Fatio) to the present day.
Did you realise that Newton was very interested in Fatio’s ideas, and that his famous dictum, “hypotheses non fingo” – “I make no hypotheses” – was more honoured in the breach than the observance! He in fact considered many. He claimed initially (see p 61 and elsewhere) to have arrived at the inverse square law of gravity from the hypothesis that aether flowed into the earth.
Le Sage’s idea, with “ultramundane particles” from the outer reaches of the universe causing gravity, has interested many notable scientists, including James Clerk Maxwell, William Thomson (Kelvin) and Hendrik Lorentz. Some, following Le Sage’s own version, assumed particles that came from elsewhere, others assumed they were both emitted and received, yet others (including Lorentz and modern contributors such as John Kierein) thought in terms of waves. Some versions of the theory involve notions such as the continuous expansion of the earth (see Martin Kokus’ contribution). Many versions imply that there should be a degree of “gravity shielding”, and experiments such as Quirino Majorana’s of around 1920 may be important here. His experiments were not in themselves conclusive, but they do show that if we go by the empirical facts we cannot rule out the possibility that the Sun’s actual density is about three times as great as we currently think.
A common idea is that the stability of planetary systems demands a central force, and this leads, as discovered by Laplace, to the need for gravity to propagate at many times the speed of light. The argument goes that it should suffer aberration and this would cause planets to accelerate and leave the system unless it was so fast that the forward component was negligible. Interestingly, Poincaré in 1906 and Jaakkola in 1996 arrived at the same solution as myself here: reluctant to assume that anything went faster than c, they preferred to postulate additional forces, counterbalancing any aberration.
No version yet has been without its problems. The popularity of Le Sage-type theories has ebbed and flowed as various notables have discredited them, “proving” that they gave impossible predictions – a crazy imbalance in the tides, for instance – and the next generation, prepared to make different assumptions, has refuted the proof and restored them to favour. (My own ideas on gravity, briefly mentioned in my Phi-Waves and Forces paper, bear some relation to them and are, just possibly, sufficiently different to overcome the difficulties.) But Einstein’s theories came into the ascendancy in the 1920’s after his dramatic light-bending success, blazoned across the headlines of the New York Times. The difficulties of Le Sage-type theories were thankfully forgotten and the world decided to replace physics by mathematics – so very much tidier!
This book
is a must for all who realise that Einstein’s approach is leading nowhere. These days we know Maxwell, Kelvin, Lorentz
and other scientists just for tiny portions of their work. Modern texts books fail to mention all their
interesting speculations – precisely the same kind of speculation for which you
and I find ourselves ridiculed if we dare to mention them in the newsgroups.