Battlefield Earth (2000)

Factual error: Amongst the essential parts of a nuclear weapon's detonation mechanism is a radioactive isotope of tritium, which has a half life of just 12 1/2 years. The tritium in every nuke on earth has to be replaced every ten years or so. This is by no means unusual; there are other perishable parts including detonators made of conventional explosives which would be completely inert after a thousand years. After lying dormant with no maintenance at all for that amount of time the nuclear weapons the 'Man-animals' find would be big shiny paperweights and not much else.

Chrissy: What if he's not dead?
Parson Staffer: Hope is an admirable quality, but foolish isn't.

Trivia: John Travolta made the film with Franchise Pictures. A few years after the film, it was revealed in a court case that Franchise had fraudulently overstated the budget of Battlefield Earth by $21 million to scam investors. After losing the case, Franchise filed for bankruptcy, and Travolta fired his manager, who set up the deal with Franchise in the first place.

Question: How did the Psychlos originally find Earth?

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