That's my question...esp. considering that many of the superconducting magnets can levitate metal objects with ease.....so, anti-grav or not?....
I would not call that anti-gravity. Gravity acts on the entire system -- the electromagnetic rails and the train -- the same as if it were a normal train. Anything that relies on forces or conservation of mass (chemical rockets, ion propulsion, orion-type bomb shockwave surfing) cannot be called anti-gravity without creating the absurd semantic situation where everything is an anti-gravity device.
Something that smooths space-time around the device, or within an imaginary surface created by the device (one side of a plane, or a cone), is definitely anti-gravity. Something that creates an artificial gravity well to offset existing gravitational forces might be anti-gravity, if it uses less than (hopefully far less than) the equivalent amount of energy (based on relativity) to create that gravity well. Including any other devices/phenomena opens the definition to enough ambiguity that the term might become useless. For instance, a device that converts energy, according to currently known physics, into a gravity well according to known equivalences, and uses that gravity well -- created by mass or energy density -- to offset existing gravitational forces, can't really be called anti-gravity either. It would have major consequences for propulsion, but if it were called anti-gravity, you could just as easily call the moon an anti-gravity devices because when you're at the gravitational midpoint between Earth and Moon, the Moon prevents you from falling back to Earth.
It might well be that there is no way to create anti-gravity devices in the sense above. I do not think the definition of anti-gravity should depend on whether it's possible. I'm more concerned with defining anti-gravity so that it doesn't encompass every force-producing physical phenomenon.
Fistful, if you have a better definition, how about presenting it?
Or when the eggheads decided that Pluto was/was not a planet,
The options the astronomical community had were either to add several other objects as planets (a term which had never previously been adequately defined) -- and probably add even more over time -- or make a one-time adjustment by excluding Pluto -- and be reasonably sure that they wouldn't have to regularly tweak the list of planets in the future.
Any change in the status quo, that we previously assumed was static, is a shock to people. I grew up learning Pluto as a planet, as did (almost?) everyone here. But our understanding of the universe changes, and we shouldn't hold on to the past simply to avoid change. "Planet" is supposed to mean something, rather than "a somewhat arbitrary list of things orbiting Sol that we picked because we saw them first". We can't have Pluto remain a planet when Eris and other dwarf planets are excluded, unless there really are qualitative differences. I'm sure the IAU looked carefully for a reasonable way to differentiate Pluto and allow it to remain a planet, but in the end they couldn't find one that was meaningful enough.
