[ExI] Von Neumann Probes

[John Clark]

On Sat, Jan 24, 2026 at 8:57 AM Jason Resch via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> More computation doesn't require more energy, this is a common
> misconception.
>

*That's no misconception, assuming you don't have infinite memory
or infinite time available, and by infinite I mean infinite and not just
astronomically large. If your memory is finite then after you finish a
calculation you're going to need to erase all the scratchpad stuff in
memory you use to produce the answer and just keep the answer, but that
takes energy. Landauer's principle allows us to calculate the fundamental
lower bound of the energy needed to erase one bit of information, it is
k*T*ln2, (K is Boltzman's constant, T is the temperature of the computer in
kelvin, and ln2 is the natural logarithm of 2). **At room temperature it
takes at least 2.9 x 10^-21 joules of energy to erase one bit of
information. Of course if you had infinite memory at your disposal then you
wouldn't need to erase anything, but unfortunately you don't. *

*There is one way around this, Landauer’s bound only applies to information
erasure not to logic steps, so if your computer is made in a way that
allows for reversible computing (everyday computers are not) then once you
finish a computation you could keep the answer and then run the computer
backwards to get back to the starting state, so no information is erased.
If you do that then, although you could never get to zero, you could
perform a calculation using an arbitrarily small amount of energy. But the
trouble is thermodynamics tells us the process needs to be as close to
adiabatic as possible, so the less energy you use the slower your
computation. Of course if you had infinite time at your disposal it
wouldn't matter how slow the computation is, but unfortunately you don't.*

*John K Clark*





>
>
>>
>>> * > I appreciate the 'von Neumann probe' argument, but not all
>>> civilisations are going to go that route*
>>
>>
>> *It would only take one. And I'm not talking about one civilization, I'm
>> talking about one individual in a civilization. It is simply not **tenable to
>> maintain that precisely 100% of the technologically savvy individuals in
>> the observable universe have decided not to make a Von Neumann Probe. I
>> think William of Ockham would agree with me that the best explanation of
>> the Fermi Paradox is simply we are the first. And as I keep saying,
>> somebody has to be. *
>>
>> *> I have a hunch that we tend to vastly underestimate the difficulty of
>>> interstellar travel.*
>>
>>
>> *You don't need interstellar travel to make a Dyson sphere/swarm, and
>> something like that should be very noticeable, but we have noticed nothing.
>> And any technological civilization worth its salt should be able to get a
>> Von Neumann Probe moving at 1% the speed of light because its mass would be
>> very small, and so it could get from one side of the galaxy to the other in
>> just 10 million years, a blink of the eye cosmically speaking. But just how
>> much would a Von Neumann Probe weigh? *
>>
>>
>> *Estimates vary, Freeman Dyson thought it would be about a kilogram but
>> George Church and Zaza Osmanov think that's much too high, they think with
>> advanced Nanotechnology one Von Neumann Probe could be about the size of a
>> bacteria and, depending on various engineering considerations, weigh
>> between a trillionth of a gram (10^-12) and a thousandth (10^-3) of a gram;
>> and, if it had access to raw materials and light energy from a star, it
>> could make a copy of itself in about a year. Then after 79 years there
>> would be an Avogadro's number of Von Neumann Probes, 6.02*10^23. And one
>> year after that it would be obvious to a blind man in a fog bank that not
>> all the technologically knowledgeable minds in the galaxy were on the
>> Earth. But we have seen nothing like that. I think I know why. *
>>
>> *John K Clark*
>> _
>
>
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