Stewart Brand

It's in a mountain in Texas and will be visible by the public sometime in the next probably 10 years.

So they had to invent, he and the team that he built around it, had to invent various things that couldn't use any kind of technology

lubrication, because that becomes a source of a problem over time.

So all of the places where there was friction, they wound up using ceramic surfaces.

And it's a skeleton clock, so you can see if anything goes wrong, you see exactly where it's gone wrong.

And there's a mountain of spare parts off in a separate part of the cave.

This is a 300 foot high thing inside a mountain.

And it resets itself to a perfectly accurate time at noon, solar noon.

typically once a year, but it can do it more often.

And that's done through a lens that lets in a ray of sunlight at the moment of noon.

And if the clock, which is operating off a pendulum, which is operating off of energy provided by a bladder of air that shrinks and

It expands because of temperature differences day and night.

That pendulum is kept going.

But it can eventually lose a few seconds one way or the other.

And then this ray of light comes in at perfect noon and resets the whole apparatus too.

perfect noon.

And there's a procession of the equinoxes that occurs over the next 10,000 years.

And that also is accounted for and managed by a cam that changes the set point exactly the rate of the procession of the equinoxes.

And so it turns out you can build

a clock that will keep ticking for at least 10,000 years, or maybe probably more, if people are interested.