Grey Goo

There is a new and highly speculative concept of nanotechnology, the creation of functioning machines that are extremely small, possibly even microscopic. At the moment we are not able to make such machines, but some scientists consider it to be a possibility.

One intriguing idea is to have these tiny machines create other machines like them, a sort of reproduction much as found in living things. Each created machine could then create its own machines, and so on.

There is a question of whether this process could get out of control, with these nanobots creating billions or trillions of copies of themselves, without stopping. The results would perhaps be a sort of “grey goo,” a substance composed completely of these nanobots. Possibly they might convert the entire Earth into this goo.

It’s fun to think about, but I think people have overlooked one obvious fact. Just as living things require food to live and reproduce, so would these nanobots. They would consume whatever materials they could use. Once they finished that, they would no longer be able to function, and the problem would stop.

Under ideal conditions, a bacterium could reproduce every 20 minutes by splitting (fission). After one hour, there would be 8 bacteria. After the next hour, 64 bacteria. then 512, 4096, 32,768… After 2 days, there would be so many bacteria that they would form a cube of 1 million kilometers on a side.

This doesn’t happen, because bacteria are almost never in ideal conditions. There are always other bacteria competing for food, or lack of food because it has all been consumed. The exponential growth stops long before things get out of hand.

Nanobots won’t form a grey goo for the same reason bacteria won’t fill the Universe. The conditions are not ideal, and they can’t be.

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