Trivia: Gene Barry and Ann Robinson, stars of the 1953 version of this movie, make a small cameo in this movie as Mary Ann's parents. They are at the end when the whole family is reunited.
Trivia: In an early scene in which Rachel is watching television, she's channel surfing. At one point, she hits briefly upon a shot of a car being demolished by a speeding locomotive. This is, in fact, a scene from "The Greatest Show on Earth," which Steven Spielberg has reported as the first movie he ever saw at a movie theater.
Trivia: When a group of aliens are exploring in the cellar, one of them spins the wheel of an overturned bicycle, and all are startled when the bicycle falls, making for a moment of comic relief. There's more to it, though. The H.G.Wells book mentions that the aliens probably had no concept of the wheel, as not a single rotating part was found inside the captured tripods. So an upside-down bicycle must have puzzled them a great deal.
Trivia: The sequence at the end, when the dying alien crawls out of the damaged machine, arm dangling, is taken directly from the 1953 original. This scene is not at all in either the book or the radio play.
Trivia: When Tom Cruise and Dakota Fanning are hiding out in a basement after the military attack, they meet a character called Oglivy. Oglivy was mentioned in both HG Wells' original book and the highly popular radio play, except then, he was a noted astronomer.
Trivia: Unlike other films where old tanks are 'built up' to look like the tanks they represent, this film is the first film to feature real M1 Abrams on camera.
Trivia: The plane crash scene that was built for this film is now part of the back-lot tour at Universal Studios. Ironically, the plane had to be repainted after the movie, as it had the logo of a real airline company, and pilots flying overhead were calling in an airline crash for that airline.
Trivia: The set used for the 747 crash cost 9 million dollars, and appears in the film for a total of 4 and 1/2 minutes. Five years after the film was made the set is still intact, and a part of the Universal Studios tour in California. There is a steep hill directly behind the "crash site" with a residential neighborhood on top. The tour guides joke that when the people living up there have something they can't get rid of in a garage sale they just toss it down the hill and it becomes part of the debris field.
Trivia: The top of the Tripods look like the spaceships from the 1953 version. The comic "League of Extraordinary Gentlemen" also had Tripods that looked like this.
Trivia: When they get picked up by the tripod, Tom Cruise destroys it by blowing it up with grenades, he lets the other people know by spitting the pins out of his mouth.Tom Cruise does this again in a later film Edge of Tomorrow at the end only this time he opens his hand to reveal the grenade pins.
Chosen answer: In the original George Pal version they were Martians and the reasoning for what they were doing was never explained. In this version, it's never explained where they come from, but their mission is simple, to eradicate human life from Earth, and use our bodies to fertilise the planet, probably so that they can colonise the planet for themselves.
GalahadFairlight
If it was to eradicate us they could have done that millions of years back, why now, so that doesn't add up.
You want to grow the substance (people) that grows your food source before using it. If they waited too much longer, they'd have a harder time because we'd have the technology to fight them back.
The reason which was apparently provided by Wells was that Mars was dying by lack of natural resources and that Martians needed a new home and food source.
They were waiting until the population grew large enough to sustain terraforming efforts. As they used our bodily fluids seemingly as a primary material for their terraforming.
It's an assumption that they could have eradicated us millions of years ago (which by the way would be long before we even existed). Maybe they didn't have the ability to transport themselves, only the machines. Maybe the original aliens all died. Lots of other options why they couldn't have done it.
They probably needed to wait for us to produce enough humans to use as fertilizer. Doesn't make sense to try to use several million bodies as fertilizer back then vs now with billions of people.