Essays on Infinite Lifespans
barbiturates, can flatten EEG (brain electrical activity) read-
ings for many hours while still permitting later recovery. 
This prolonged drug-induced elimination of brain activity is
sometimes used as a treatment for head injuries.  Patients
do not emerge from these comas as blank slates. Evidently
human beings do not require continuous operation like com-
puter chips. Brains store long-term memories in physical
structures, not fleeting electrical patterns.
Perhaps the most extreme example of brains completely
stopping and later starting again are the experiments of Isamu
Suda reported in the journal Nature  and elsewhere 
in 1966 and 1974. Suda showed recovery of EEG activity in
cat brains resuscitated with warm blood after frozen storage at
-20°C (-4°F) for up to seven years.
Reversible experiments in which all electrical activity stops,
and chemistry comes to a virtual halt, disprove the 19th-cen-
tury belief that there is a spark of life inside living things.
Life is chemistry. When the chemistry of life is adequately
preserved, so is life. When the chemical structure and orga-
nization of a human mind is adequately preserved, so is the
Sudas frozen cat brains deteriorated with time. Brains
thawed after five days showed EEG patterns almost identical to
EEGs obtained before freezing. However brains thawed after
seven years showed greatly slowed activity. At a temperature
of -20°C, liquid water still exists in a concentrated solution
between ice crystals. Chemical deterioration still slowly occurs
in this cold liquid.
Preserving the chemistry of life for unlimited periods of
time requires cooling below -130°C (-200°F).  Below this
temperature, any remaining unfrozen liquid between ice crys-
tals undergoes a glass transition. Molecules become stuck to
their neighbors with weak hydrogen bonds. Instead of wan-