From: hal@finney.org
Date: Sun May 14 2000 - 21:35:53 MDT
Quoting Hal:
> > This is not an early or intermediate level of nanotech development.
> > It would be among the most sophisticated nanotech applications imaginable.
> > By the time such a global system could be designed, developed and put
> > into play, gray goo could have wiped out the world ten times over.
Robert B. replies:
> I disagree strongly with this as I've said in another post. Our *current*
> sensing technology is more than sufficient to detect very small hot spots.
Keep in mind that the paragraph preceding my comment envisioned an active
defense which regularly entered every eukaryotic cell on the planet and
inspected it for goo. That is what I was referring to as an advanced
nanotech application.
> (I'm sure Spike could comment here.) If there is reason to suspect
> covert activities, we could easily launch equivalents of the Space
> Infrared Telescope and turn them around to study earth. It goes without
> saying that we are not even completely aware of the sophistication
> of our existing detection capabilities. Considering the rapid
> progress in photon detectors (i.e. astronomers couldn't buy for
> any price a 3 million pixel CCD 10 years ago, and now we have them
> in consumer devices), I have little doubt that our detection capabilities
> will be up to the task.
>
> With sufficient monitoring capacity we would know the *day* anyone
> released badbots on the planet.
With sufficient monitoring capacity, any information gathering is possible
in principle. So this last statement is too broad to be very useful.
But if we are talking about early or intermediate nanotech, and our
monitoring is restricted to detecting temperature anomalies, I don't
think this is effective against some of Robert Freitas' scenarios.
Assume that the goo seeds are spread widely before beginning their
growth phase. Robert F. suggests dispersal by airplane. Perhaps it
would work to spread rock-coated nanites in the form of dust released
into the atmosphere from a few locations over a period of many months.
We now have potentially billions or even trillions of nucleation sites.
Each of these begins to grow simultaneously, not caring about local
thermal pollution, but limited by some constraining temperature, such
as the boiling point of water. (We cook our food before eating it;
perhaps the goo will find it more tender that way as well.)
According to Robert F.'s figures, this will not cause a noticeable (4
degree) global increase in temperatures until something like 0.0001%
of total biomass has been converted. Due to the wide dispersal,
localized hot spots may not be detectable either. At this point the
global temperature will rapidly increase to 100 degrees C. If I am
reading Robert F.'s equations right, this requires only a six to seven
doublings by the goo[*], a matter of minutes.
At this point the growth rate ramps down and the remaining conversion
takes three weeks so we don't burn our food. Of course by this time
the temperature has killed all life anyway.
I don't see how particle beams and similar technologies can deal with
an attack of this sort. The goo sites are too numerous and widespread,
and the time from thermal detection to total destruction of the biosphere
is too short.
Hal
[*] Replication time of 100 seconds, T = 300 K, and dissipation of 100
MJ/kg implies 5x10^10 kg of nanotech according to the paper. This is
5x10^18 J per 100 seconds or 5x10^16 W. Solar power is 1.75x10^17 for
a total power input of 2.25x10^17. Power scales as the fourth power
of temperature. For T = 285 K, the "four degree" detection threshold,
power would be (285/300)^4 less, or 0.80 * 2.25x10^17 = 1.8x10^17.
Subtract 1.75x10^17 for solar to get the nanotech contribution of 5x10^15
W, one tenth of the level needed for 300 degrees. Similar calculations
for 373 K, the boiling point of water, require total power (373/300)^4
more, or 2.34 * 2.25x10^17 = 5.26x10^17. Subtract the solar contribution
to get 3.51x10^17 W for the nanotech. This is 7 times the 300 K figure.
Therefore the difference between the four degree increase tempearture
of 285 K and the boiling point temperature of 373 is a total factor of
about 70, or 6-7 doublings.
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