What is the Meaning of "Empty Space"?

In summary, "empty space" can refer to a region that contains no matter but possibly has fields such as an electromagnetic field, or it can refer to a region that contains no matter or fields. The term is often used in the context of spacetime models, and should not be confused with the interior or exterior regions of a black hole model.
  • #1
ValenceE
142
0
Once again, hello to all !:smile: ,

I'm back with another quick question ...

Can you explain or redirect me to an explanation of what the term ' empty space ' means.

It’ all over in the threads I read, but it’s not quite clear to me as to what it pertains to …


Thank you,

VE
 
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  • #2
"Empty" space is a theoretical construct that does not exist in our Universe. Even in the absence of matter and radiation, "empty" space is a teeming sea of virtual particles, coming into existence and annihilating in accordance with the Heisenberg Uncertainty Principle. You might think that for "something" to exist, there must be a "nothing" with which to contrast it, but that is not the case.
 
  • #3
In general, "empty space" is a term used when the space baing refferenced is devoid of anything that would effect the outcum of the scenario in question.
 
  • #4
ValenceE said:
Once again, hello to all !:smile: ,

I'm back with another quick question ...

Can you explain or redirect me to an explanation of what the term ' empty space ' means.

It’ all over in the threads I read, but it’s not quite clear to me as to what it pertains to …


Thank you,

VE
In quantum physics (or quantum field theory), 'empty space' means actually 'vacuum' and means the state of lowest energy (which is non-zero). So, empty space means in fact the sea (or soup) of virtual particles poppping in and out of existence.
 
  • #5
To quote Steven Hawking: "Empty space isn't empty"
 
  • #6
"Empty space" in the context of gtr?

ValenceE said:
Can you explain or redirect me to an explanation of what the term ' empty space ' means.

Since you are posting in the relativity forum, I will guess that you have encountered this phrase in the context of spacetime models, probably solutions of the Einstein field equation. If so, "empty space" refers to some region which contains no matter, but possibly contains some field such as an electromagnetic field (which will not interfere with uncharged test particles, except indirectly via the gravitational effects of the electromagnetic field energy). A "vacuum" region almost always refers to a region which contains no matter and no non-gravitational fields. Some authors use "empty space" as a synonym for "vacuum". An "electrovacuum" region contains only a gravitational and an electromagnetic field.

Examples of regions in a spacetime model which would NOT be called "empty space" under any circumstances include "balls of perfect fluid". Such fluid balls are often used to construct simple models of isolated stars by "matching across the surface" (where the pressure of the fluid falls to zero) to an "exterior vacuum region". Similarly, collapsing balls of pressureless perfect fluid, or collapsing "dust balls" for short, are often used to construct simple models of gravitational collapse by matching across some (topologically) spherical surface (the pressure is everywhere zero in the dust, so we have a lot of freedom here) to an exterior vacuum region.

In the context of stellar models or collapse models, you might see the terms "interior solution" (perfect fluid) and "exterior solution" (vacuum, or sometimes, imprecisely, "empty space"). If so, don't confuse these with discussion of the "interior region" versus "exterior region" of a black hole model; these would generally both be regions of "empty space"; their common boundary is the event horizon of the black hole.

Chris Hillman
 

Related to What is the Meaning of "Empty Space"?

1. What is empty space?

Empty space, also known as vacuum, is the space in the universe that contains little to no matter. It is characterized by a lack of particles and energy, and is considered to be a void or absence of anything physical.

2. Is empty space truly empty?

While empty space does not contain any matter, it is not completely empty. According to quantum mechanics, space is filled with virtual particles that pop in and out of existence, creating a constantly fluctuating energy field.

3. How is empty space related to the concept of nothingness?

The concept of nothingness is often associated with empty space, but they are not necessarily the same. Nothingness implies a complete absence of anything, while empty space still contains energy and virtual particles.

4. What role does empty space play in the universe?

Empty space is an essential component of the universe as it provides the medium through which matter and energy can interact and move. It also plays a crucial role in the expansion of the universe.

5. Can empty space be manipulated or harnessed for practical use?

Despite its seeming emptiness, empty space has been harnessed for practical use in various fields of science and technology. For example, it is used in vacuum technology, particle accelerators, and in the study of quantum mechanics.

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