richardt@orstcs.UUCP (richardt) (08/07/85)
Somebody mentioned that Gravity acted only on matter. The one catch is, the equations which make up Einsteinian (?) physics all depend on matter being interchangeable with energy, where gravity is defined as a form of energy. T'other catch is, those fundamental equations also state that all energy is interdependant, and we'll know how when we get a working Unified field Theory. BTW, we can make black holes. It just takes far to much effort to build one at this late date in man's exploration of space. orstcs!richardt "Women should be obscene but not heard" -- Jubal Harshaw, _Stranger_in_A_Strange_Land
john@hp-pcd.UUCP (john) (08/08/85)
<<< < < Somebody mentioned that Gravity acted only on matter. The one catch is, < the equations which make up Einsteinian (?) physics all depend on matter < being interchangeable with energy, where gravity is defined as a form of < energy. < A good example is the planet Vulcan (Yes there really was one). One of the best ways to discover a new planet was to chart the orbits of the known planets and see if you could spot any perturbation in their orbit that might be caused by an unseen neighbor. Several of the outer ones were discovered using this method. Anyway, someone noticed that Mercury had a wobble in its orbit that suggested another planet orbiting between it and the Sun. This "planet" was dubbed Vulcan and astronomers tried unsuccesfully for years to try and find it. It turned out that the wobble was due to the gravitational effect from the "mass equivalent" of the suns gravitational field. The energy in the field was equivalent to a certain amount of mass and if you considered the effect of this mass the mercury was doing what it was supposed to do. A more complete disscussion can be found in Asimov's "The Planet that wasn't". John Eaton !hplabs!hp-pcd!john