Can a Perfect Vacuum be Created & Stretch Space? Answers Here!

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Discussion Overview

The discussion revolves around the feasibility of creating a perfect vacuum in a closed pipe with a piston and the implications of moving the piston, particularly whether this action could be interpreted as stretching space. Participants explore the mechanics involved, the forces at play, and the theoretical aspects of space stretching under various conditions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether a powerful engine can pull a piston any distance along a pipe closed at one end, considering the implications of creating a perfect vacuum.
  • Another participant suggests that the problem is not special and asserts that the force required to pull the piston is equal to the air pressure acting on it, regardless of the distance.
  • A different participant provides an analogy involving a pipe filled with air submerged underwater to illustrate the pressure dynamics at play, indicating that the force required would be similar in both scenarios of atmospheric pressure and perfect vacuum.
  • One participant explicitly states that moving the piston farther in a perfect vacuum does not equate to stretching space.
  • Another participant expresses uncertainty about the conditions under which space could be stretched, mentioning extreme scenarios like black holes or relativistic speeds.

Areas of Agreement / Disagreement

Participants express differing views on the concept of stretching space, with some asserting it is not applicable in this scenario, while others suggest that unusual conditions might allow for it. The discussion remains unresolved regarding the implications of moving the piston in a vacuum.

Contextual Notes

Participants do not reach a consensus on the nature of space stretching, and there are varying interpretations of the forces involved in moving the piston. The discussion includes assumptions about pressure dynamics and the theoretical implications of vacuum conditions.

richard hunter
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I have no qualifications in science but find it fascinating in general. Could anyone answer the following for me?

Imagine an immensely strong pipe closed at one end with an airtight piston pressed tightly against the closed end.

(a) Is it possible to pull the piston any distance along the pipe using a powerful engine?

(b) If so, is there a limit as to how far can it be pulled?

(c) Assuming a perfect vacuum is created, would moving the piston farther be stretching space?

(d) Is it possible to stretch space under any conditions?

Thanks
 
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This is not such a special problem. Even if the piston and the bottom of the cylinder were a single piece (or welded together) you can break them apart. This is done routinely by the machines used to test tensile strength.
If you worry just about the pressure of air on the other side of the piston, you only need a force equal to whatever air pressure force is on the piston.
How far does not matter, the force is the same.

There is nothing about "space stretching" in this.
 
Here's something that may help you 'feel' how it'd be.

Imagine you take the same pipe+piston, only filled with air at normal atmospheric pressure, and submerge it 10 metres deep in water.
Since at that depth the pressure is equal to about twice the atmospheric pressure, the difference in pressures between outside and inside of the pipe would be 1 atm. I.e., the same difference as in the scenario you described, with a pipe with perfect vacuum inside and air outside.
That piston would be just as hard to pull 10 metres deep in water as it would be with perfect vacuum on the surface, and the pipe just as likely to collapse.

If you replaced the air inside with vacuum, and take the setup underwater, it'd require just twice the force from the previous case to move.
 
richard hunter said:
(a) Is it possible to pull the piston any distance along the pipe using a powerful engine?

What force do you think has to be overcome? Typically it's only the air pressing on the outside of the piston (say about 15lbs per square inch).

(b) If so, is there a limit as to how far can it be pulled?

No. Except perhaps the size of the universe?

(c) Assuming a perfect vacuum is created, would moving the piston farther be stretching space?

No.

(d) Is it possible to stretch space under any conditions?

I don't think that's easy to answer. Really strange things happen near a black hole or when traveling close to the speed of light.
 

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