They weren't just mining rocks/minerals on Praxis. "Praxis is their key energy production facility. ..." - Sulu

So they were mining something with a lot of energy. Not dilithium, it would seem. Maybe something like the Cylons were after on Carillon, which exploded after Starbuck/Apollo ignited underground fires with their "lasers."

Also, Praxis was "just" a moon, not a big planet.

(Yes, I know Carillon was also a planet, but different show, different rules. )

Spock said Praxis exploded because of over-mining, not an energy source.. I maintain that, with thousands of Horta making tunnels, Janus 6 would eventually be hollowed out to the point of breaking up, It might take centuries, but it would happen. Even if it didn't, the Horta would, again, possibly after centuries, run out of rock to tunnel through. They would have no choice but to live in an oxygen atmosphere. They have no technology, so relocating to another planet isn't possible.

Yes, it was over-mining and inadequate safety precautions, OF THEIR KEY ENERGY PRODUCTION FACILITY. Not just rocks and minerals. (Or as Kelly Bundy used to say, "vitamins and rocks.") If it was just rocks etc, then in theory I suppose a planet could end up hollowed out and eventually collapse. But it wouldn't explode in some kind of fireball. Although if it was hollowed out, where would the gravity come from to make it collapse? Gravity comes from mass, after all. I suppose it could end up a hollow shell, in theory, but there would be insufficient gravity and other problems, long before then.

I didn't say collapse. I said break up. The gravity of its sun might cause a hollowed out planet to break up or possibly a moon(s) if it had any

Oh because of tidal forces etc? I suppose that might happen, if it somehow happened suddenly. But as the planet was consumed, its mass - and hence its gravity - is reduced, so even if it HAD a moon it would lose the moon long before it was "hollow," because it would lack the gravity to hold a moon in orbit. I'm not Rajesh Koothrappali so I won't claim to know for sure what would happen to the planet's orbit around the sun as its mass decreased. But since whatever mass remains would still be moving at the same orbital velocity, it seems most likely that it would move farther and farther from the sun. Which means tidal forces would diminish too. But other things could happen as it moved out, including a collision with another planet if they happened to cross orbits.

Okay, Knix. We can at least agree that something catastrophic would eventually happen to Janus 6 if the Horta tunneled long enough.

After Horta 'eat' the rocks, there is eventually, um, what we might politely call an output from the, er, other end of the Horta. This, shall we say, discharge, would in some part replenish the planet's mineral content, as, indeed, dead Horta would, as well. Circle of life, bud - carbon beings like us poop carbon to replenish our carbon-based ecosystem, and silicon critters like the Horta poop silicon and other minerals to help replenish their silicon based ecosystem. And there is a whole lot more matter in the planet's mantle than on the surface; "eventually" in this case is a long, long, long time. The liquid core of the planet would, in all likelihood, move to the mantle, cool, and effectively replace the material removed by the Horta. A long, long, long, long time.

Hadn't thought of that. Interesting idea. I always assumed most of the Horta's bodily processes turned most of its food intake into its incredibly strong acid. And we don't know for sure that Janus 6 has a liquid center.

Fair enough; the planet could have a solid core - but, if so, that would be effectively more food for the Horta.

Let's also consider the possibility of other silicon-based life within the planet. The Horta probably wouldn't have developed in isolation - maybe there are the equivalent of Silicon "plants," which grow like crystals, creating more food for the Horta. I think it's possible to imagine other ways a silicon based ecosystem could resupply the silicon necessary to sustain silicon-based life. My own belief is that there must be some balance in nature, and, in this case, balance means there must be a way to replenish the silicon needed to sustain a healthy ecosystem. But, yeah, that's completely speculative, so it's just a theory.

But it's a good theory, jx. Thanks for the input.

A lot of the replenishment of matter on Earth is due to energy from the Sun. Not sure how that would work for silicon based life. Also if the hortas are digesting rock, maybe it's not all silicon.

And if Janus 6 didn't have a molten core, seems like it would end up being too cold even for horta to survive, especially underground without some way of absorbing whatever solar energy might be available on the surface.

And if Janus 6 didn't have a molten core, seems like it would end up being too cold even for horta to survive, especially underground without some way of absorbing whatever solar energy might be available on the surface.

Good point.

EEEEEWWWWW!! I just conjured what jx's theory postulates. Eventually, the Horta would be eating their own fecal matter. GUHROSS!

BTW, Knix. Bones was absolutely sure a silicon lifeform couldn't exist. He was wrong about that, so he could also be wrong about the Horta existing in an oxygen atmosphere. It's not canon, but in several of the 80's novels, there was a Horta serving on Big E named N'Hrat or something like that. In one, Bones was treating him for iron deficiency by feeding him iron.

@Jetfire59 said:

EEEEEWWWWW!! I just conjured what jx's theory postulates. Eventually, the Horta would be eating their own fecal matter. GUHROSS!

BTW, Knix. Bones was absolutely sure a silicon lifeform couldn't exist. He was wrong about that, so he could also be wrong about the Horta existing in an oxygen atmosphere. It's not canon, but in several of the 80's novels, there was a Horta serving on Big E named N'Hrat or something like that. Bones was treating him for iron deficiency by feeding him iron.

Really only after it had been "recycled" by various planetary processes. We do the same thing, of course. The main difference is that our "recycling process" includes a lot of solar energy input, which may not be the case for the horta.

And I'm far more likely to dismiss novels than any of the series episodes, or what was said in them. I find it especially easy to dismiss Lt. Dolphin or whatever. That fits in with what I've commented elsewhere about people making up ridiculous crap just because they think "It's a cool story."

What's next, Lt Blowhole, the humpback whale who was so grateful about Kirk rescuing his/her species that it had to join up to "give something back?" Bah.

And I'm far more likely to dismiss novels than any of the series episodes, or what was said in them.

Thus my statement that the novels are not canon. I wasn't using it at an argument. I was just offering an interesting footnote. You went adversarial here, not me. Can you not participate in any discussion without resorting to ridiculing whomever you're talking to?