Continuity mistake: Once Ray takes the piece of pita with hummus and eats some of it, the rest of the pita and the way he holds it differs in following shots. (00:12:30)
Continuity mistake: After Ray finds out that Robbie took the car, he runs into the street. In the first shot he stops at least 6-8 ft away from the solid double street lines to turn, yet in the next shot he's standing right on the double lines. (00:13:25)
Continuity mistake: When Ray runs into the street he realizes that everyone is looking behind him, towards his house, so he turns to the right and looks over his right shoulder, but in the next shot facing his house, he's turning to the left and looks over his left shoulder. (00:13:30)
Continuity mistake: After Rachel tells Ray that Robbie took the car, when Ray runs down the steps long shadows are cast. When Ray turns around to see what everyone is looking at, all shadows are gone, only to reappear in the next shot. Then when Ray runs to his yard, the angle of his shadow is entirely different. (00:13:30)
Continuity mistake: When Ray runs behind his house to have a better view of the sky we can see from behind that his hood is blowing in the wind. When it cuts to a shot in front of him his hood is still. (00:13:40)
Continuity mistake: When Ray is in his backyard and says, "That is so weird," he's standing well away from the fence that is near the female neighbor holding the baby, but in the next shot he's right beside the fence talking to her. (00:14:35)
Continuity mistake: When Ray and Rachel are in the backyard, just before the lightening starts, she says, "I don't wanna go by myself," and there are no leaves on the barbeque. In the next close-up, as they stand near it, there are leaves on it. (Not due to wind.) (00:15:35)
Continuity mistake: When Ray and Rachel crawl under the kitchen table during the lightning strikes, in the first shot Ray's entire body is behind the leg base, yet in the next shot his arms and upper body are in front of it. (00:16:15)
Audio problem: At the beginning when Robbie runs up to tell Ray what happened with the car, and they're standing in the middle of the street, when Robbie says, "It opened up this hole or something," his lips aren't in sync with the words. (00:18:15)
Continuity mistake: When Ray runs out of the house and meets up with Robbie, the cars and pedestrians very noticeably differ between consecutive shots while they talk. (Not due to cars being pushed.) (00:18:15)
Continuity mistake: As Ray says, "Next time you take my car with no driver's licenseĀ " he walks a good distance away from Robbie. Yet in the next close-up of Robbie, Ray's arm is still pointing up near Robbie's face. (00:18:25)
Continuity mistake: After speaking with Robbie, when Ray runs across the street to speak with Manny some are entirely different cars from the previous shots and in one case a car jumps sideways from one lane to the next. Ray also runs beside the crosswalk in the close-up, but in the next shot he's much farther away, and the crowd differs. (00:18:50)
Continuity mistake: When Ray runs across the street shouting, "Manny! Manny!" a guy with a hat and plaid jacket passes by, as the shot ends. At the start of the next shot, the same guy is now near Manny's garage door and air hose. (00:18:55)
Continuity mistake: As Ray heads to the 26 strikes spot, while speaking with the two guys, he passes many stalled cars, some of which change entirely between shots. For example: In the close-ups he passes a red car in front of the restaurant, with a grey double parked car, and a white car at the street corner in front of the red, yet in the overhead shot a red car is at the street corner, with a grey car behind, in front of the restaurant. (00:19:30)
Continuity mistake: When Ray and the two guys head to the spot with 26 strikes, there is a crowd of people walking behind them in all the close-ups, yet, in the overhead shot hardly anyone is behind them as they approach the hole, and there was no time for the crowd to move ahead or disperse. Additionally, some of those people who are already positioned at the center of the crowd, around the hole, were just behind Ray in the previous shots. (00:19:35)
Continuity mistake: When Ray reaches the red church at the beginning of the film, the sun changes positions three or four times behind the tower of the church. (00:20:10)
Continuity mistake: When Ray and others are crouched beside the hole in the asphalt, the guys around him and the way he holds the freezing piece of asphalt, differ between consecutive shots. (00:20:50)
Continuity mistake: As the hole begins to crack in the overhead wideshot the crowd moves back, and the florist is at the top center of the screen with hardly anyone near it. Yet, in the next close-up, suddenly there are dozens of people standing in its path, as the crack dramatically approaches the florist. (00:21:15)
Continuity mistake: When the hole cracks the asphalt in the first shot, the crack makes its way to Santo's Florist cracking the side of the brick building. A few shots later, when the Portuguese restaurant windows shatter, as the camera pans toward the church Santo's is seen on the street corner and the massive damage to the building is gone. The long crack in the asphalt leading from the hole to the florist is gone too. (00:21:20)
Continuity mistake: As the asphalt begins to burst open, the Portuguese restaurant's windows shatter, and when the camera pans to the church there are very few people on the street in front of it. In the next shot, however, there is a huge crowd in front of it. (00:22:10)
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.