TANSTAAFL "There Ain't No Such Thing As A Free Lunch"
" "Oh, 'tanstaafl'. Means 'There ain't no such thing as a free lunch.' And isn't," I added, pointing to a FREE LUNCH sign across room, "or these drinks would cost half as much. " -- Manuel, The Moon is a Harsh Mistress (1967), pg 129, Robert A. Heinlein
Simply put, it means that one cannot get something for nothing. Even if something appears to be free, there is always a catch. You may get free food at a bar during "happy hour," but the bar-owner gets some sort of benefit such as attracting new customers. This may or may not be true at the individual level, depending on the interpretation of the phrase. Though it is possible for an individual to get a "free lunch" (as when a company cuts its costs and gains competitive advantage by polluting the air), someone ends up paying the cost of the "lunch."
Months pass and the Revolution may be running out of steam. Then the invasion from Earth happens. Avoiding Mike's radar, ships land and troops enter Luna City. They are wiped out to a man. In other warrens the result is the same, although the details differ. Loonie casualties are very high, but the invasion is stopped dead. Revolutionary troops deal with ships on the surface and in orbit using mining lasers. In one warren, Churchill Upper, air pressure is lost and many perish. The news is spread that Adam Selene is one of the casualties. This removes the need for Adam to appear in the flesh, or even by video. Selene is more valuable as a martyr than as a "talking head".
The failure of the invasion is, in hindsight, no surprise to the revolutionaries. The troops were not used to the low gravity. They could not run from one position to another, especially when descending ramps. Their weapons, firing bullets, shot high. Loonies, furious when roused, attacked with any available weapon in defense of their homes. Even when gas was used the invaders lost.
Mike initiates Luna's response. Cargoes of rocks are targeted to sparsely populated locations on Earth with warnings to stay away from those places transmitted to the news media. People ignore the warnings and go to the targets to watch the show. As a result, thousands die. Public opinion on Earth is now in favor of wiping out the new nation. Even some Loonies are dismayed. The revolutionaries know it is too late to turn back. The bombardments continue.
Mannie is sent to run the guidance computer, a former bank accounting machine, at the new secret catapult. While there he learns that another attack has taken place, using nuclear weapons. The original catapult has been destroyed. Cut off from the rest of Luna, he keeps firing rocks even while Earth's news media tout the end of the Lunar Menace. Once Earth is convinced the rocks will not stop (in actuality, Luna is quickly running out of missiles), one nation after another recognizes the new nation. At last, Earth capitulates.
Mannie returns in triumph to Luna City. Professor Bernardo de la Paz, as leader of the new nation, proclaims victory to the crowds gathered in the warren's largest public space, and then collapses and dies. Mannie takes over briefly, but soon steps aside in favor of other revolutionaries. Mannie and Wyoh eventually retire from politics. The Davis family elects Stu LaJoie as a new husband.
Mannie realizes that the destruction of the original catapult was part of Prof's plan, kept secret even from Mannie and Wyoh. With no convenient transport to the new catapult, it will be impossible to export grain in any significant quantity until Earth has a chance to build a return catapult, assuring that Luna will not run out of food or water. But Prof saw Luna's future as a transport hub, not as a farm.
Mike is gone. In the final attacks (Mannie, with communications cut off, did not learn of them until he returned to Luna City), the Authority Complex was badly shaken although all Mike's hardware remained intact, buried deep in a chamber designed to withstand nuclear attack. However, Mike's personality is gone. He functions perfectly, but as a computer.
In the final paragraphs (set, as is the novel's first paragraph, many years after the other events), Mannie complains how the Lunar government is always passing taxes and regulations, and ignoring all the Professor's ideas. There is a "Sons of the Revolution" meeting that night, and Mannie considers going but thinks better of it. Loonies are moving out to the asteroids. Maybe he'll go with them...
"My word, I'm not even a hundred yet."
Charybdis - TANSTAAFL