Spike Jones, <email@example.com>, writes:
> ok now go back down the scale. we are accustomed to getting power
> from violent chemical reactions such as octane and air, but a plant can
> get all the energy it needs from photosynthesis. plants on our scale
> generally need a lot of leaves, but single celled plants have so little
> chlorophyll they sometimes dont even look green, and yet they seem
> wildly active under a microscope. chlorophyll creates sugars, which
> break down in a much gentler reaction than oxygen combustion.
Our chemical reactions are violent in part because we don't have the technology to extract the energy efficiently, the way plants do. We have to burn gasoline or other fuels to produce heat in a rather crude way.
> so, if the lesson of nature is not misleading, we dont need nanonukes,
> or even nanoscale combustion. the square cube law would suggest
> that nanobots should be able to create all the energy they need using
> chlorophyll and the fusion reactor nature has already generously
> provided: the sun. right? spike
The square-cube law says that smaller units have a larger surface area per volume. If sunlight is proportional to surface area, then this does give an advantage to smaller entities. But that is only true for those entities in favorable positions to get sunlight. If you have a solid mass of nanomachines, then the ones in the middle don't get any light. So you still have an energy problem.
In fact, if we think of the surface of the nanomachines as being where energy is expended, then smaller units will have a bigger energy problem, because they have more functional area but a smaller volume to power it with.
So there does seem to be a power question with regard to nanobots. Solar is an option for those outside, as long as they are in a thin layer. In other environments they will probably need a fuel supply of energetic chemicals.