will have to be made of unobtanium anyway, and that'll be an excellent substance to line the tunnels with :-)

The ultimate version would then be: a Straight Line from, e.g. New York to London. Hm, no ref. materials handy; what would the depth at midpoint be? The angle at the endpoints?

Another hmmm -- could be a bit difficult to allow for things like slippage of crustal joints, etc. etc. in the rock at shallow depths. The relatively plastic magma might actually be a safer surround, given that ::languid handwaving:: the heat and pressure can be withstood by the ::slightly less languid handwaving:: beta-unobtainium hydroxysilicate tunnel wall material.

I and others have been offering that, or something very akin, as a justification for space research for many years.

No good. Thou shalt not pollute the virgin Mohorovic Discontinuity, thou anti-Gaia Corporate Troll.

Ah well. It ain't that simple^SM

No, it won't work. As our society gets more complex, and the bits accessible to everyone [or mostly everyone] get more powerful, the need for trust amongst the members increases. Unfortunately it also reduces the amount of work or other input required, and people get lazy.

The real trouble comes in with, ah, metathoughts, if you will [ok, stupid concept; best I can do]

That is: Ordinary [!] carelessness, inattention, ignorance, etc. etc. is less a problem than deliberate violations of the trust relationship. The "system" has grown up with continuous negligence in the background, and has ways of handling the problems, mostly social -- although certainly there is a real necessity for keeping the equipment and knowledge around for cleaning up the spills and routing around the resulting holes. I don't know any way we could do it without the ever-popular --

Back to the cave! Man Was Not Meant To [X]. This, once the shibboleth of the ignorant Religious Fundamentalist, has now become the axiom [that which cannot be proved, but is true anyway] of people who are contemptuous of the ones who originated the notion. But we changed the name! they cry.

When you have people who want to question the whole basis, and are willing to break things and/or hurt people to support their beliefs: what do you do? What is the right way to handle people whose ethic is that the lovely thing about the interlocking web of trust relationships is that you can do so much damage by betraying the trust?

Back in the Sixties my grandmother asked me a question I couldn't answer right away. She was watching the space launches, and was genuinely and sincerely worried. Were those people breaking God's law by traveling in outer space?

It took some thought, but finally I told her that God's Creation involved, among other things, gravity, and that NASA had literally teams of people whose job it was to insure that no attempt was ever made to violate God's Law of Gravity in the slightest way. --It satisfied her enormously. After that, she thought the space program was great.

Frequently the problem is simple ignorance. I could probably be persuaded to start shooting people who promote ignorance as a desirable state, and there are lots of them about.