Sorry, I should have said that there were about 1000 different sets, with ratios measured to about 5 digits of accuracy each... your point about the gravitational redshift is well taken. On Apr 3, 2015, at 9:12 PM, "Keith F. Lynch" <kfl@KeithLynch.net> wrote:
Cris Moore <moore@santafe.edu> wrote:
The first seismic tests have succeeded in returning a signal. It turns out that there are two sets of tuning forks deep in the bedrock, whose resonant frequencies appear to be incommensurable. When their ratio is expanded in binary, its first few thousand digits reveal an image of an eldritch race, barrel-shaped creatures with pentagonal symmetry and diaphanous wings... who knows what secrets are buried deeper inside its binary expansion.
How long would you have to listen to two tuning forks to measure their relative frequencies to a few thousand binary digits? Remember that the sphere is at most two or three billion years old (2^51 seconds), and that frequencies above about 100 MHz (2^24 Hz) won't propagate through rock.
Extreme frequency stability would also require an absurdly high Q, but at least that would mean that there's no need for seismic excitation. The aliens who buried the thing set it to resonating, and it's still resonating. But for it to emit one watt of acoustic power for a billion years (10^16.5 seconds) it would have to have started with at least 10^16.5 joules of kinetic plus potential energy. That energy, by E=mc^2, has a mass of about a third of a kilogram. The gradual loss of that mass would greatly change the resonant frequency.
Also, if the two tuning forks differ in altitude by even one centimeter, that would throw off the frequency ratio by about one part in 10^18, i.e. 54 binary digits, due to general relativity's gravitational time dilation.
The article was of course a joke, but I tried to make it physically possible. (Similarly with my proposal to speed up the Earth's rotation by running tidal power stations in reverse; that would actually work, though you would need to build lots of large new stations.) Indeed, I'd like to see someone try something like Project Durin. I think it has just as much chance of working as radio-based SETI searches, and would be a lot less expensive.
If I could find a good venue (this probably isn't it), I'd like to have a discussion of how workable the idea is. Would such a sphere be stable for hundreds of millions of years at the temperatures and pressures in the upper mantle? What would the signal strength of such a tuning fork be, and would it be lost in the background noise? How much information could be practically encoded with multiple tuning forks in such a sphere? Information could be encoded with frequency, location within the sphere, and polarization. (Sounds in solids have three possible polarizations.) Has anyone made an acoustic search for such spheres? Is the idea really original with me?
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