Based the author's eperiments and extensive searchers in the scientific literature, ,he concludes that vacuum is not a void , but rather a concentrated matrix of protons and unpaired electrons, possibly Bose-Einstein Condensed (BEC) hydrogen. It may be the aether of classical physics and /or the dark matter, for which Astronomers are searching. The book attempts to explain many observed phenomena, on this basis, including: Magnetism Gravity Light Stellar Aberration and Einstein's Twin Paradox