There is a technology, still in the embryonic stage, called nanotechnology.
It has been proven theoretically possible, but we are still anywhere from 5
to 100 years or more away from actually being able to use it. Basically this
technology involves building molecule size machines which would be used to
build things - cars, TVs, buildings, anything at all - atom by atom. These
machines will also be used to repair things - especially the human body.
This will enable people to prolong their lives perhaps for hundreds of years.
Also, it will allow people who have been preserved cryogenically or
otherwise to be revived and cured of whatever illness or disorder they had.
But - and this is where it gets really interesting - this technology will be
able to revive people from death. Scientists believe that memory is
dependent on the arrangement of cells in the brain. If this order can be
preserved after death, then nanotechnology could go through and repair every
cell in a body, thus reviving someone who was dead. This person would have
all of their memories and personality intact.
There are chemicals with which someone can be embalmed today that will
preserve the molecular structure of the body. If you plan ahead, you can
plan to have yourself revived, or your uncle Milt, or whoever.
I have no idea, though, what the Torah or Midrash would say about this.
Tom RuBane
By the way, the authoritative book on the subject is Engines of Creation
by K. Eric Drexler. It is written for a non-technical audience, and is
very interesting.