I'm watching 2001: A Space Odyssey, and I'm confused about what physically happened
to cause Poole's death.
I understand that
Poole somehow had his oxygen tube disconnected. But why is he suddenly flying off into space? And why is the pod doing the same?
It seemed the pod was very far away from Poole when all this happened, so I don't understand how it influenced the situation.
Poole was Killed by HAL. As the entire ship and mission is under complete control of HAL then it can basically do anything. My read on the situation is that HAL caused the pod to 'attack' Poole, thus disconnecting his oxygen tube and 'shoving' him off into space. Because in the 2001 universe, the rules of physics are strictly adhered to (unlike most sci-fi), once Poole was on his way there was no way to stop him, let alone catch him.
In the book, there's an line after Poole is killed saying (something like) 'Frank Poole became the first person to reach Jupiter'.
Edit I wasn't quite right ! Dave Bowman did catch Poole but not before his oxygen ran out. See this from Wikipedia:
In an act resembling human desperation, HAL rams Poole with one of the spaceship's EVA pods, severing his oxygen hose and sending Poole hurtling into outer space without his oxygen. Bowman, in a second pod, races from the Discovery One to retrieve Poole, but is unable to reach him before Poole runs out of oxygen.
In this clip you can see what happens:
Poole exists the pod and as he's making his way to the antenna, the pod slowly begins to turn behind him. Then the camera view switches and the pod completes its turn, starts extending its manipulator arms and "lunges" toward the camera. Then the shot of HAL's red eye, watching what happens, and then Bowman seeing Poole flying away on a monitor, then the shot of Poole with the air line detached and so on until he stops moving and you see him and the tumbling pod moving away.
The implication is quite clear: HAL sent the pod after Poole to hit him to fling him away from Discovery and used the manipulator arms to pull the air line. It wasn't shown, but if this were another genre of movie and Poole was a swimmer and you saw a shark's fin behind him, then a cut to someone watching with a horrified look, then cut back to only showing a spreading slick of blood on the water, you don't need to see the actual attack to figure out what happened.
In the film, HAL accelerates the pod toward Pool while simultaneously opening the pod's manipulator claws, reminiscent of a swooping eagle's talons opening to grab prey. When the pod hit Poole, it had built up a high speed. Its momentum at impact was enough for the manipulator to sever Poole's oxygen line and send him flying out from the Discovery. The pod's impact with Poole deflected it and started it spinning as it moved away. HAL let the pod go because there was no further use for it.
I'm not sure, but when I watched it the pod was piloted by HAL. However, when you pay attention, the pod slowly lurks at Frank. Then we see him trying to put the air tube to his tank. I think the pod hit Frank, dislodging the tube shooting them both way from the ship.
