Interstellar Movie - Conservation of Angular Momentum

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Discussion Overview

The discussion revolves around the portrayal of angular momentum conservation in the movie Interstellar, specifically regarding the mechanics of a spacecraft that begins to rotate to simulate gravity. Participants explore the implications of initiating rotation without apparent external torque and the principles of angular momentum conservation.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions how the spacecraft could increase its angular momentum from zero without external torque being applied.
  • Another participant draws an analogy between linear momentum and angular momentum, suggesting that rockets can change their linear momentum without violating conservation laws, implying a similar principle applies to angular momentum.
  • A different participant clarifies that the conservation of angular momentum applies to the entire system (rocket plus expelled gases), indicating that the gases expelled from the engines carry opposite angular momentum, thus conserving the total angular momentum of the system.
  • Another participant introduces the idea that rotation can also be controlled using gyroscopes or flywheels, suggesting alternative methods for achieving rotation without rockets.

Areas of Agreement / Disagreement

Participants express differing views on the mechanics of angular momentum conservation in the context of the film, with no consensus reached on the initial question regarding the spacecraft's rotation.

Contextual Notes

Participants discuss the closed system concept, indicating that the ship alone does not represent a closed system without considering the expelled gases. There is also an implicit assumption about the absence of external torques that may not be fully explored.

robbertypob
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OK, so I'm right in the middle of watching Interstellar and I've just seen the part where they have docked with the 'mothership' and they fire up their engines to get it to rotate. This is so they can generate a centrifugal force to simulate gravity.

My question is - first the ship was not rotating and they took action to make it rotate. How could this possibly be? Angular momentum started at 0 and was increased without any apparent external torque being applied.

Please could somebody help me out?
 
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robbertypob said:
How could this possibly be? Angular momentum started at 0 and was increased without any apparent external torque being applied.
Do you understand how rockets increase their linear momentum, without violating momentum conservation? Angular momentum is analogous.
 
Whole system(rocket + gases, which came out of engines) angular momentum was conserved. Gases, which came out of engines got opposite angular momentum.

Just like linear momentum is conserved when rocket accelerates - gases ,which come out of engine get opposite linear momentum,so whole system linear momentum is conserved.
robbertypob said:
My question is - first the ship was not rotating and they took action to make it rotate.
Only the ship is not closed system. Closed system is ship +Gases ,which come out of engines.
 
Last edited:
Even without rockets you can control a craft's rotation using gyroscopes/flywheels.
 

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