Vibration in vacuum. What would happen?

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    Vacuum Vibration
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Discussion Overview

The discussion explores the behavior of vibrating objects, specifically a guitar string, in a vacuum. Participants examine the implications of a lack of air and contact on the persistence of vibrations, energy dissipation, and the nature of a perfect vacuum.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that a vibrating guitar string in a vacuum would continue to vibrate indefinitely due to the absence of air and contact.
  • Another participant counters that the string would not vibrate indefinitely, as energy would dissipate within the string itself due to its imperfect elasticity and the rigidity of its mounting points.
  • It is noted that energy conversion to heat occurs in the string, with steel strings dissipating energy slowly compared to nylon strings, and that friction between the string and the guitar body contributes to energy loss as heat.
  • A participant mentions that thought experiments often assume perpetual motion when external factors are removed, referencing Newton's principles.
  • Questions are raised about the nature of a perfect vacuum, with one participant inquiring what constitutes a perfect vacuum and what exists between atoms.
  • Another participant clarifies that a perfect vacuum is defined as the absence of matter, without introducing concepts like dark energy or matter.

Areas of Agreement / Disagreement

Participants express differing views on whether vibrations in a vacuum would persist indefinitely, with some arguing for energy dissipation and others suggesting perpetual motion in thought experiments. The nature of a perfect vacuum also remains a point of inquiry without consensus.

Contextual Notes

Participants acknowledge limitations in measuring energy dissipation accurately and the complexities involved in defining a perfect vacuum.

uros
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Place a guitar floating in the vacuum. Once one string start to vibrate it would not stop since there is no air and contact. So any object vibrating in the vacuum would continue to vibrate indefinitely or the energy would become heat and radiation?
 
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It wouldn't vibrate indefinitely - quite a bit of the energy would be dissipated in the string itself. The string is not perfectly elastic, and the mounting points on both ends are not perfectly rigid, so the string would indeed slow down and stop.
 
As cjl said, some of the energy will be converted into heat inside the string itself. For steel strings this would happen very slowly, but it would be faster for nylon strings. No material is perfectly elastic, and if you measured the force and displacement very accurately, you would see that the graph when the force decreases does not lie exactly on top of the graph when the force increases. In fact, the (small) area between the two curves is a measure of the amount of mechanical energy that is "lost" and converted to heat.

Another (and probably quicker) way that the energy would be turned into heat is by friction. The vibrating strings move slightly backwards and forwards over the bridge and the top of the fingerboard with each cycle of vibration, The joints between the different parts of the guitar body will also move slightly relative to each other, etc, and everywhere this happens there will be a friction force that does work and generates heat.

All those effects are also happening when the guitar is not in a vacuum, of course. You may have assumed that all the energy in the string was converted into sound energy but I bet you never did an experiment to measure whether that was a good assumption. (It would be quite a difficult experiment to measure this accurately, though)
 
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In thought experiments, things tend to happen forever if you take away all the factors that would impede them.

That statement is basically just a generalization of Newton...
 
if every thing in the universe is made up of matter? what would it be a perdect vacuum made of? dark energy and matter? and what's between antoms? perfect cacuum?
 
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el.fisico said:
if every thing in the universe is made up of matter? what would it be a perdect vacuum made of? dark energy and matter? and what's between antoms? perfect cacuum?

Everything within the universe =/= the universe.

What's between atoms? Well you've read the response to the exact question in the vacuum thread.

A perfect vacuum simply lacks matter, that is all.
 

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