Understanding Velocity: The Perspective of Fish in a Tank

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Discussion Overview

The discussion revolves around the concept of velocity as perceived by different observers, specifically using the analogy of fish in a tank and an owner observing them. It explores the implications of different frames of reference and the relativity of motion, touching on both Newtonian physics and broader philosophical questions about motion in space.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that each fish perceives its own velocity relative to the other fish, raising questions about the nature of absolute velocity as measured by an external observer.
  • Another participant introduces a scenario where an external observer (the owner) may also be moving, complicating the determination of which entity is actually in motion.
  • A third participant proposes that the discussion should be redirected to a more appropriate forum focused on Newtonian Physics or Mechanical Engineering, implying that the question may be better suited for technical expertise.
  • Further, a participant critiques the initial analogy, asserting that it relies on Galilean relativity and emphasizes that the fish tank serves as a useful frame for the owner but may not be universally applicable.

Areas of Agreement / Disagreement

Participants express differing views on the validity and implications of the fish tank analogy, with some agreeing on the relativity of motion while others challenge the assumptions made about preferred frames of reference. The discussion remains unresolved regarding the nature of absolute velocity and the applicability of the analogy in broader contexts.

Contextual Notes

The discussion highlights limitations in understanding motion across different frames of reference, particularly the assumptions regarding the observer's motion and the implications of using a specific frame as a reference point. There are unresolved questions about the nature of absolute velocity and the relevance of the fish tank analogy in various contexts.

rab99
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If i have two fish in a fish tank say fish A and fish B and the owner of the tank is looking into the tank

each fish thinks he is traveling at some velocity.

fish A looks at fish B and Fish A doest know if he is moving or if fish B is moving. Same for fish B. But the owner looking into the tank can absolutely tell which fish is moving.

As I said in another post two frames of reference are always conatined within a third larger frame.

can someone explain to me why the perspective of the fish is the preferred frame?

the owner measures the fishs velocity and call him on this two way radio and tells him his velocity. Is this an absolute velocity?
 
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In your example, the owner would just happen to be moving as fast as the fish he thinks is not moving. What if the owner's friend was walking by the fish tank, walking as fast as the "moving" fish? Now take this into space. Which fish/person system is moving and which is not?
 
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This question should be moved to the forum on Newtonian Physics or Mechanical Engineering. Any engineer who designs moving machinery can answer it.
 
DocZaius said:
Now take this into space.
Indeed: who owns space?!

Rab, we are quite clear on how you think the universe works. It doesn't work that way. There really isn't anything to be gained by repeating your misunderstanding over and over and over again. We get it, but it doesn't get any less wrong the more often you repeat it.

Perhaps you learned something though: your fish tank example utilizes Galilean relativity (I mentioned this before). I'm not quite sure you're completely there, though: your fish tank is a "preferred" frame only insofar as it is useful for the owner of the tank to measure the speed of the fish with respect to the water in the tank. But it still doesn't necessarily make any sense for others to use that frame. And that's perfectly fine.
 
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