My experience with Alta Vista was that sometimes it seemed to go "off-track", answering, not my question, but a similar question. When I tried to refine my query, it still seemed stuck on what it thought I asked before, not what I was asking.
I later found out that they used "Bayesian Logic", where the answers to the previous questions guided the answer to the new question. No wonder I had this problem!
When Google came along, of course I went with them, and still do. They are still the #1 Search Engine, although some of their other services, like Google Maps, have become untrustworthy.
In ten years, this can replace existing passenger and freight rail, and displace a lot of air travel. In forty years, this could be a multi-trillion dollar industry satisfying most of the county's transportation needs cleanly and efficiently.
One of the strange things about a tachyon is that it can be traveling in one direction for some real inertial reference frame, and be traveling in another direction for some other inertial reference frame. For yet another reference frame intermediate between those two, the tachyon is traveling at infinite speed, yet has zero dynamic mass and a finite momentum of +/- i mc, where i is the square root of -1, m is the imaginary rest mass of the tachyon, and c is the speed of light.
The direction of the momentum vector is ambiguous.
Since this is a total contradiction, I assume that tachyons cannot exist.
It has also been alleged that H2 is a greenhouse gas.
Another point — there has been some work on converting light and water directly into H2 and O2 gas much more efficiently that powering electrolysis from photovoltaic electricity.
I'm a Lisp variable -- bind me!