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∂AIL Professor Holt Ashley↓Department of Aeronautics and Astronautics↓Durand Room 369
↓Stanford University↓Stanford, California 94305∞

Dear Holt:

	Here is a copy of the Sawyer paper.

	The critical very long term issue is whether there are unsubstitutable
nonrenewable resources.  According to present science, the nuclear and
gravitational energy of the stars is such a resource, but its time scale is
billions of years.  At present, I see no convincing scientific case that
there are any others.

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	On the other hand, many resources are nonrenewable in our present
way of using technology.  Consider for example carbon compounds.  Many of
them are made from natural gas which posesses not only carbon and hydrogen,
but also nicely packages the energy required for the chemical transformations.
Clearly, hydrocarbons won't last long as a source of energy, but will have
to be replaced by nuclear and maybe solar.  If we use coal, oil and gas
only as a source of chemicals, they will clearly last much longer, but
eventually we will have to retrieve carbon from the atmosphere where most
of the carbon that flows through our technology ends up.  This seems to be
quite feasible using plants, although it seems difficult to do it directly,
because CO2 forms only .03% of the atmosphere.  However, the problem is one
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that won't become acute for several hundred years at the very least, and
our descendants will be smarter than we are.

	Incidentally, could you send me a copy of my letter, because the Xerox
machine where I was in Japan is under the control of a bureaucracy I couldn't
easily bring myself to face, so I didn't make a copy, and I fear that I
may have been repeating myself in the last paragraph.

	Can we get together for lunch sometime?  I have been asked by
%3American Scientist%1 to put my lecture "The Scientific Basis for
Technological Optimism" into written form, and I want to get a number of
points of view before I finish it.  

.reg