At the beginning of the film it is said that the Bellus-Zyra system has moved 1.6 million kilometers in just two weeks. Later, it's said the system will cover the 4,800 million kilometers to the Earth in less than one year. At the speed implied by the first statement, the arrival to the Earth would take some 115 years.
In the rocket, when Dr. Drake tries to convince Randall to go on the trip to Zyra, Eddie is referred to as Eddie Cummings. Later, in Hendron's office, he is called Eddie Garson. To make things more confusing, Eddie's girlfriend is Julie Cummings.
When the main characters are gathered in Hendron's office awaiting the passing of Zyra, Joyce is seated in a chair. As the earthquake starts, she rises and runs across the room to Dave Randall. A short time later, in a shot from another angle, she's seated again then rises and runs to Randall a second time.
Joyce is wearing only one earring when she and Randall are riding in the taxi.
The vehicles next to the ship at the final loading disappear just before take-off (even though the ramp gate was locked and there is no reason why they should have been moved).
The passengers of the spaceship transporting them to Zyra are told that it is not known whether Zyra has a breathable atmosphere. Aside from the fact that it would make little sense to travel to a world without knowing whether it was habitable, even in the early 1950's astronomers would have been able to perform a spectroscopic analysis of Zyra's atmosphere and determine whether it contained oxygen and was breathable.
There are no external fuel tanks visible on the spacecraft (think of the space shuttle as a reference), implying that all the fuel is carried internally. The spaceship is simply too small to carry 40+ humans and a small zoo of animals, plus the enormous quantity of fuel required for the takeoff/flight.
While a planet making a close pass at Earth would effect the tides and cause disruption, the film presents it incorrectly. The disruption would not occur at one moment. There would be a build-up of disruption in the tides until the planet makes its closest pass, causing maximum damage.
Bellas is said to be "a dozen times the size of earth." As such, it would not be big enough to support nuclear fusion.
When describing the location of the approaching star, the constellation is given as Scorpio. The correct name for the constellation is Scorpius. Scorpio is used as an astrological sign associated with the constellation.
The red handrails on the gangplank disappear when the men board the ship. They re-appear when the ship has landed on Zyra. It's logical that the tubular railings plug into points on the ramp, and were removed to be stowed after loading the animals and women, then put back after the ramp was deployed on Zyra.
People are visible in the black and white photographs of supposedly deserted New York. The reporter stated that some utility workers had volunteered to stay behind. Even when a city is evacuated, there can always be a few stragglers.
It is said that if the Bellus-Zyra system stays in the Solar System, retained by our Sun, the temperature on the surface of Zyra, where the human race begins a new existence, would suffer a harmful increase because of the presence of two suns. However, Bellus does not stay in the Solar System; it is also destroyed when it collides with Earth. Therefore, there will be no second sun in the Solar System and no increase in the temperature of Zyra.
When the spaceship lands on the new world, the landscape is covered in ice and snow. When the spaceship opens, however, that landscape is verdant, with only traces of snow. In fact, the edge of snowcap is clearly seen outside the door to the ship, leading to the green areas just beyond. Obviously the ship has landed at a place where the snowcap ends.
The Argentinian delegate's placard at the UN says "Argentine" instead of "Argentina" (though this country's official designation is, in fact, "Argentine Republic").
When the male new arrivals enter their room, one poor guy, in the bottom right of the screen, opens his suit case on the top bunk. We can clearly see the suit case is empty. He then shuts the suit case and checks the firmness of the bunk.
At approximately two and a half minutes into the film, Randall is seen behind the controls of an aircraft with a woman sitting beside him. If you look carefully at the sky visible behind them the clouds are going the wrong way, as if he is flying the plane backwards.
When the rocket takes off, we have been told that the g-force will be high enough to cause everyone to black out, as indeed they are shown to do. But their postures show no sign of acceleration, nor are their faces distorted as even a few g will do.
When Tony Drake and Dave Randall leave Hendron's office after Stanton shoots Ferris, the shadows of the actors can be seen crossing the painted backdrop outside the window.
On the new world there are ruins of a vast and clearly artificial edifice on the left, with rectangular openings, along with a pair of pyramidal structures, center, that no one appears to notice.
When the panicking crowd shoots at the ship before takeoff, the bullets bounce off the skin. Construction of this type would be immensely heavy, and it would be imperative that the ship be as light as possible.
The rocket is built in the open, with no cover or hangar over it, subjecting it to rain, dust and other corrosion causing agents.
The scientists often state to the world the effects of Zyra's bypass occurring at a precise 1pm. They should be specifying either a time zone or GMT (Greenwich Mean Time).
It appears that the designers of the ship forgot to include landing gear for it. Even skids would have sufficed, instead of belly landing the ship.
As the rocket approaches Zyra, David Randall tells the pilot to cut engines one and six, which he does. But David's lips said "one and two," not "one and six."
When Dr. Hendron activates the ship's launching mechanism, Stanton tries to wheel himself to the ramp and says "No! Wait! Help!". However, his lips do not match him saying "help".
Throughout the film, Bellus is referred to as a star; this is presumably how life is able to be sustained on Zyra. However, if this was the case, Earth would have been destroyed from the heat long before Bellus collided with it, even if it was a small brown-dwarf star. Also, departure should have been at least 17 days earlier, before descending deep into Bellus' gravity well and needing far more fuel. This part of the plot, and the time to build the ship, could have been resolved by sticking to the novel's pair of planets and a longer time frame - Zyra and Bellus both passing by with Bellus, a gas giant planet, ripping up Earth's surface, then returning months later for Bellus' direct collision with Earth, as Zyra enters orbit around the sun.
There were strict limitations as to the number of people who could board the ship bound for Zyra due to weight concerns, yet at the last minute a dog is allowed on board with no concerns as to the extra weight. If that were so, then certainly a human infant should have been given preference to the dog.
The ejecta from Earth's collision with Bellus would have both destroyed the rocket ship and obliterated the surface ecology of Xyra (if not the entire planet), thus dooming mankind to extinction.
When Hendron opens the door and pulls the lever to free the ship for launch, it appears that nobody anticipated this having to be done, as nobody is near who would have been assigned to do it. Additionally, as he pulls the lever, the gangplank is retracting, which means that anyone who had the duty of unlocking the ship would have been left behind.
There is no reason for Randall, who is just a courier, to be present at the top-secret meeting taking place while Bronson's data is being verified.
When Joyce and Randall are in the cab, they are discussing top secret information about the end of the world and they are speaking in normal voices. Although it isn't part of the story line, the cab driver could have heard them.