Can You Compress a Vacuum Void?

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Discussion Overview

The discussion revolves around the nature of a vacuum, particularly in the context of compressing a vacuum within a piston and its implications for understanding physical laws and the universe's origins. Participants explore theoretical and conceptual aspects of vacuum, including its properties and the forces that maintain it.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants question how a vacuum, defined as the absence of matter, can have properties like volume and existence within physical laws.
  • Others argue that compressing a vacuum does not make sense since a vacuum is 'nothing' and cannot be compressed, only the volume of the chamber can be reduced.
  • A participant suggests that if a piston is isolated from outside air pressure, compressing the vacuum would not change anything except the volume of the void.
  • Some participants clarify that the vacuum in outer space is maintained by gravitational forces, which prevent the atmosphere from dispersing into the solar system.
  • There is a discussion about the terminology of compression, with some asserting that you cannot compress a volume itself, only the contents within it.
  • Participants debate the definitions of compression and whether it applies to materials or volumes, with references to physical definitions and examples.

Areas of Agreement / Disagreement

Participants express differing views on whether a vacuum can be compressed and the implications of that compression. There is no consensus on the definitions and interpretations of compression in relation to vacuum and volume.

Contextual Notes

Participants highlight the importance of terminology when discussing vacuum and compression, indicating that misunderstandings may arise from differing definitions and assumptions about physical concepts.

  • #31
OK so you now accept thermal expansion as a physical fact.

Slide a loose fit ring onto a metal bar.

Heat the bar, but not the ring (eg by heating the bar at a reomte end).

The ring now becomes a tight fit or even a very tight fit.

Do you deny this to be a physical fact?

The bar is now under two dimensional compression from the ring.

Examples in nature abound.

This is junior high school physics.
 
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  • #32
Studiot said:
OK so you now accept thermal expansion as a physical fact.

Slide a loose fit ring onto a metal bar.

Heat the bar, but not the ring (eg by heating the bar at a reomte end).

The ring now becomes a tight fit or even a very tight fit.

Do you deny this to be a physical fact?

The bar is now under two dimensional compression from the ring.

Examples in nature abound.

This is junior high school physics.

Again, I ask if this is actually compression. I'm not denying anything, I actually don't know. When I looked up what compression was, I posted the definitions I got. Can you show me something that says that compression doesn't always result in reduction in volume?
 
  • #33
Since you like online and eschew libraries try googling thermal stress.

Here is the first definition on page 1 of a very long list

(mechanics) Mechanical stress induced in a body when some or all of its parts are not free to expand or contract in response to changes in temperature.




http://www.answers.com/topic/thermal-stress
 
  • #34
And how does that relate to compression?
 
  • #35
Have you done the 'research' I suggested?
 
  • #36
I've looked at a few of the results. Nothing I've seen contradicts my previous posts however. I'm not seeing the relation between thermal stress and compression. There is definitely stress that is placed on the object, but I don't see how that is compression. At least in a way that doesn't contradict the definitions of Compression that I've found. It's simply stress.
 
  • #37
I suggest you bone up on the meaning of stress, paying particular attention to the types of stress.

There is no such animal as 'simply stress' in the physics dictionary.
 
  • #38
Can you answer this? If the volume of the object isn't reduced, is it still compression? Not compressive stress, not thermal stress, but compression. Everything I've read says no, but I could always be wrong. The answer to that would solve all this.

And "simply stress" means that its just stress, whatever the type.
 
  • #39
I have answered it more than once, and I grow weary of repeating myself.

Technically, Compression refers to the application of compressive stress. Period.

Not volume change, not heating, not plasticization or any of the other effects that may or may not accompany the application of that stress.

Colloquially, many effects are associated with or substituted for compression but that is loose phraseology, unacceptable in technical usage.

A body can undergo compression without change in volume.

A body can undergo volume change without compression.

The two are separate effects that may or may not be associated.

A similar confusion often arises with the difference between heat and temperature, which are also misused synonymously.
Heating a body, may or may not result in a change of temperature, once again they are different physical quantities with separate properties in their own right.
You may be more familiar with this confusing pair.
 
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  • #40
Drakkith said:
Can you answer this? If the volume of the object isn't reduced, is it still compression? Not compressive stress, not thermal stress, but compression. Everything I've read says no, but I could always be wrong. The answer to that would solve all this.

And "simply stress" means that its just stress, whatever the type.

If an object is under a compressive stress, it is in compression. It's a pretty simple definition.

Therefore, an object can be in compression (and thus it can be compressed) without ever having shrunk in volume.
 
  • #41
Sorry, I disagree, as everything I've looked up says you must reduce something in volume to compress it. I'm not simply making this stuff up or misunderstanding it. The actual definitions in multiple sources, online and offline, even in the dictionary here at work that we have, all say that it must be reduced in volume to be compressed. Thats what Compressible itself means. Capable of being compressed. If you can provide some solid evidence, then I wil listen to it.

And this is my last post here in this thread, as it is going nowhere and I don't feel like arguing anymore over something so minor.
 
  • #42
Drakkith said:
If the piston was isolated so that there was no outside air pressure acting on it, then nothing would happen. The piston would move in and out and nothing would change except for the volume of the void would get smaller and larger as the piston moves in and out.

When talking about volume and distance, it doesn't matter if there is anything in that space or not, it makes no difference.

Edit: What makes you think that the universe originated from nothing? It's entirely possible that there have been an infinite number of big bangs followed by collapses in the past. (Though current evidence doesn't quite support this)

That is entirely and irefutably fals...In order to compress vacuum you need to change your perspective regarding forces...Let's say that the piston succesfuly vacuums your recipient , and that is where his functions stop.the piston keeps the vacuum constant while the "walls" of your recipient perform the same action by pulling them self away away from the epicenter of the recipient...in esence it creates a nother "presure point" of vacuum. In reality , my dear friends , that vacuum created is actualy the non-rezidual , non-depending and self existing force of compresion. Why ? expanding matter in order to create vacuum is the actual dilation of the matter itself ... you can call the outer-force acting apon the recipient as being a vacuuming action , but the main force , predominant in existence and the sole action manefesting inside the recipient , is actualy ... dam.dadada ta ta taaaaaaaaa! Compresion :)) because it compresses the remaining rezidual matter inside the recipient that could not be vaccumed ...in other words... it thin's and expands matter... you can not call vacuum that witch is not anti-matter...do not confuse vacuum with void... Regards ... Rares Manon Prunca
 
  • #43
I don't fully understand the line you are taking, but its seems interesting. Can this property of a vacuum fit into an ex-nihilo from nothing (or from a vacuum) explanation for the origin of the universe?
 
  • #44
NeilWallace said:
I don't fully understand the line you are taking, but its seems interesting. Can this property of a vacuum fit into an ex-nihilo from nothing (or from a vacuum) explanation for the origin of the universe?

What property of a vacuum?
 
  • #45
Hi, Prunca's definition of a vacuum. 'A non depending and self existing force of compression'. I don't know if it is crazy or not. But my own hunch as to how things got started was something similar. has to do also with the relationship between a vacuum and matter. Or if compression of a vacuum can cause matter in some way. Kind of the the original idea of this thread. But I didnt quite understand Prunca's definition.

Hmm just googled it and there's something called vacuum fluctuations as a first cause, so there's at least a few 'crazies' out there with a similar idea. Will investigate further some day.. :)

Dont mind getting shot down in flames..
 
  • #46
NeilWallace said:
Hi, Prunca's definition of a vacuum. 'A non depending and self existing force of compression'. I don't know if it is crazy or not. But my own hunch as to how things got started was something similar. has to do also with the relationship between a vacuum and matter. Or if compression of a vacuum can cause matter in some way. Kind of the the original idea of this thread. But I didnt quite understand Prunca's definition.

Hmm just googled it and there's something called vacuum fluctuations as a first cause, so there's at least a few 'crazies' out there with a similar idea. Will investigate further some day.. :)

Dont mind getting shot down in flames..


Embrassing "crazy" ideas of other people , who just so happens to have a bigger fan club because of there primordial existence in the world of physics does not make you the flaming arrow of my demise ... by the way , friend , imitation is in fact the first form of inteligence ...

Keep at it ! :)
 
  • #47
Is this the sort the thing the OP is asking about? http://www.astro.ucla.edu/~wright/cosmo_constant.html" by Baez.
 
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  • #48
Thats getting close I think. But its way beyond my understanding - 'How can nothing weigh something' - or how can a vacuum have mass, cool..! The possibilities of that concept and if it can be recreated in a lab seem intriguing..!

I'll understand it properly one day..
 

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