Translational movement of a signal atom in a vaccuum?

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Discussion Overview

The discussion revolves around the behavior of a single atom isolated in a vacuum within a Faraday cage, specifically focusing on its translational movement and the effects of energy, gravity, and wall interactions. The scope includes theoretical considerations and thought experiments related to motion in a vacuum.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that the atom would bounce around like a billiard ball, maintaining its initial kinetic energy until it encounters the walls of the container.
  • Others argue that without nearby interactions from other atoms, the atom's vibrations may not contribute to its movement in a meaningful way.
  • A participant suggests that the atom would travel in a straight line at constant velocity until it hits a wall, where it would bounce off and continue this motion.
  • Concerns are raised about the sustainability of the atom's energy for bouncing, questioning whether it would eventually run out or become unusable for continued movement.
  • Some participants note that energy transfer could occur during bounces, particularly if the walls are at absolute zero, potentially leading to the atom settling on the floor.
  • One participant asserts that gravity should act on the atom, suggesting it would bounce in parabolas, while another counters that variations in the gravitational field would affect this motion.
  • There is a discussion about the implications of Newton's first law, with some participants clarifying that an object in motion remains in motion unless acted upon by an external force.
  • Further exploration includes the initial energy of the atom and the material and temperature of the walls affecting its motion.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the atom's behavior in a vacuum, particularly concerning the effects of energy transfer, gravity, and the nature of motion without external forces. The discussion remains unresolved with no consensus reached.

Contextual Notes

Limitations include assumptions about the idealized conditions of the vacuum and the Faraday cage, as well as the effects of wall material and temperature on the atom's motion. The discussion also reflects uncertainty regarding the implications of gravitational variations within the container.

AtrusReNavah
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I had a thought-experiment I was pondering the other day. If you could somehow isolate a single atom inside a vacuum inside a Faraday cage, how would that atom behave in terms of translational movement?
 
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It would bounce around like a billiard ball with whatever initial energy it had.
 
But there's nothing to "push" against? It's all alone and doesn't have the nearby interactions of other atoms to make its own vibrations "count" so to speak. Or at least this is my question.

(a la similar to one trying to run on ice)
 
It would not vibrate. It would travel in a straight line at constant velocity until it encountered the wall of the tank, then it would bounce off in a new direction and continue again in a straight line at constant velocity until it hit another wall of the tank. etc...
 
AtrusReNavah said:
But there's nothing to "push" against? It's all alone and doesn't have the nearby interactions of other atoms to make its own vibrations "count" so to speak. Or at least this is my question.

(a la similar to one trying to run on ice)

Objects in vacuum push do not push against anything. They move inertially in a straight line until they meet a resistance.

And the atom under observation had some amount of kinetic energy before you removed all the other atoms. It keeps that kinetic energy.
 
Yes, but if its energy to "bounce" is from its initial kinetic energy when you got it in there, how does it keep bouncing? Wouldn't this energy eventually run out/not be useable for the same kind of movement?
 
AtrusReNavah said:
Yes, but if its energy to "bounce" is from its initial kinetic energy when you got it in there, how does it keep bouncing? Wouldn't this energy eventually run out/not be useable for the same kind of movement?

Every time the atom bounces off the wall there is the possibility of energy transfer from the atom to the wall or from the wall to the atom. If the wall is kept at absolute zero then the atom will eventually transfer all of its energy to the wall and settle onto the floor. It not the atoms of the wall and the atom in the tank will maintain the same average temperature.
 
Yeah. Wot he said.
 
Fantastic, thanks. :)
 
  • #10
Your posts seem to suggest (sorry if I misinterpreted) that you think an object needs to be constantly supplied with energy to stay in motion. This is untrue. An object in motion will stay in uniform motion unless acted on by an external force. This is Newton's first law.
 
  • #11
Gravity should be acting on the signal atom. The atom should bounce in perfect parabolas (and I rarely use the word perfect).
 
  • #12
Not quite perfect. There will be variations in the strength and dirrection of the gravitational field from place to place inside the container. But since we're talking about 1 atom in a perfect vacuum we must be talking about an idealized, not realistic, senerio anyway.
 
  • #13
Matterwave said:
Your posts seem to suggest (sorry if I misinterpreted) that you think an object needs to be constantly supplied with energy to stay in motion. This is untrue. An object in motion will stay in uniform motion unless acted on by an external force. This is Newton's first law.

I was assuming as stated earlier that when it "bounced" some of that energy would be transferred.

Really though what I was interested in was if gravity could pull it to the bottom.
 
  • #14
AtrusReNavah said:
I was assuming as stated earlier that when it "bounced" some of that energy would be transferred.

Really though what I was interested in was if gravity could pull it to the bottom.

It would indeed follow an arc, but you cannot discount the initial energy it had. You also cannot ignore what the walls are made of and what temperature they are at.
 

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