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.
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.
According to the time line the project to build the spaceship must be done in 8 months. That is simply not enough time to build a spaceship of that magnitude and complexity. Even in the 21st century it can take 4 to 10 years to build a spaceship.
(at around 54 mins) Dr. Hendron puts his hand over the gorgeous vintage 1940s Shure Brothers 708 A microphone he's holding, which would cause massive feedback and squeal if the microphone were actually connected to a PA system. It is also clear that there the mic is not connected to PA system when he is speaking prior to this because the sound of his voice is the same as it is in any other scene in the movie and does not sound amplified through remote speakers.
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.
On the new world there are ruins of a building on the left with rectangular openings which would indicate intelligent life that no one appears to notice which would be an important finding. There also 2 pyramids, the same size, next to each other located on the backdrop of the new world.
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 it is all ice and snow. When the spaceship opens, the landscape is all green. In fact, the edge of snow cap 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 snow cap ends.
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.
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 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.
When the ship is making its final approach to Zyra, you can see some of the black thread holding the miniature. Also, when the ship finishes skidding on the snow you can see the fishing line that dragged the model across the snow.
In two shots of the escape-shuttle nearing the new planet Zyra, the first shot shows an angled front-view of the ship entering the frame from the right, and the very next shot shows Zyra on the left and an angled from-the-rear-view of the ship approaching it from left-to-right, but the background stars are exactly the same (from the same viewing-angle) in both shots.
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.