<p>No. Space isn't empty. There are atoms. The density varies quite a lot, from a million atoms per cubic centimeter to fewer than one per 100000 cm³. Mostly this is in the form of hydrogen.</p>
<p>And there are photons, neutrinos, dark matter (whatever that is), electromagnetic field...</p>
<p>Moreover on a larger scale there are particles of dust, and of course at an even larger scale, there are stars and planets in space.</p>
<p>Space is much more empty than the atmosphere, but it isn't completely empty.</p>

CC BY-SA 4.0
2022-10-04T15:55:32.390Z
+1, but note that 10,000 cm⁻³ is _dense_ in astrophysics!
pela
CC BY-SA 4.0
2022-10-07T20:48:51.100Z
Ah, sorry, I read it as "10,000 per cm$^3$". You're right, one per 10,000 cm$^3$ is not dense (although still an order of magnitude denser than the average density).
pela
CC BY-SA 4.0
2022-10-03T18:53:31.970Z
2022-10-07T21:28:30.857Z
2022-10-07T21:28:30.857Z
James K
<p>Well there is radiation from CMB, maybe near a galixy a magnetic field, you have virtual particles, here is an interesting video <div class="youtube-embed"><div>
                <iframe width="640px" height="395px" src="https://www.youtube.com/embed/PhfqdBk8qxk?start=0"></iframe>
            </div></div></p>

CC BY-SA 4.0
2022-10-03T16:43:35.427Z
2022-10-03T16:43:35.427Z
martín canullán
<p>While I believe this is a matter of semantics, in a meaningful, physical sense (with regards to quantum field theory) space is never really empty. Quantum fields exist everywhere, and particle pairs spontaneously come in and out of existence all the time, with effects that are measurable (e.g. vacuum polarization screening on particles). These fields fluctuate and correspond to the elementary particles that we are familiar with, such as neutrinos, photons, electrons, etc. they carry energy, and some have a vacuum expectation value that is non-zero.</p>
<p>Photons fill what would otherwise be considered ‘empty’ space as well, with at the very least the CMB being (almost) isotropically found.</p>
<p>In essence, while an area may not have macroscopic objects that you can see with the naked eye, I think one could comfortably say there has never been a ‘truly’ empty part of the universe, ever, because of the presence of these quantum fields.</p>

CC BY-SA 4.0
2022-10-04T15:57:09.517Z
@PrincePugs This is a good answer, but note that good old atoms are still ubiquitous in space; see James K's answer.
pela
CC BY-SA 4.0
2022-10-26T20:56:12.173Z
@pela Yes, I know. I meant about the space that filled in where there wasn’t any atoms.
Prince Pugs
CC BY-SA 4.0
2022-10-03T19:10:59.773Z
2022-10-03T19:16:12.897Z
2022-10-03T19:16:12.897Z
Justin T
<p>So I have been thinking about this question for like five minutes. Is ‘space’ really empty? I know that technically there aren’t atoms in deep space and that would make it empty, but there has to be something to fill in those those gaps, right? So technically space isn’t empty?</p>

CC BY-SA 4.0
2022-10-03T16:11:53.503Z
There are some atoms, practically everywhere there are a few. But even atoms are mostly empty. And that empty space is empty.
Topcode
CC BY-SA 4.0
2022-10-03T17:39:22.823Z
Yes, space is pure emptiness. That's why, in my and many other peoples view, the universe must be *literally* infinite since emptiness can't just stop.
White Prime
CC BY-SA 4.0
2022-10-03T19:40:00.390Z
Then what fills in the emptiness? Dark matter? If so, what’s dark matter?
Prince Pugs
CC BY-SA 4.0
2022-10-05T19:26:03.907Z
@PrincePugs 'there has to be something to fill in those those gaps, right?'   What makes you think this?
Dave Gremlin
<space>
Is space really empty?
Prince Pugs
# Is space really empty?

(Asked by: username_0 on 2022-10-03)

So I have been thinking about this question for like five minutes. Is ‘space’ really empty? I know that technically there aren’t atoms in deep space and that would make it empty, but there has to be something to fill in those those gaps, right? So technically space isn’t empty?

**Tags:** space

> **Comments:**
> **username_1**: There are some atoms, practically everywhere there are a few. But even atoms are mostly empty. And that empty space is empty.  
> **username_2**: Yes, space is pure emptiness. That's why, in my and many other peoples view, the universe must be *literally* infinite since emptiness can't just stop.  
> **username_0**: Then what fills in the emptiness? Dark matter? If so, what’s dark matter?  
> **username_3**: @username_0 'there has to be something to fill in those those gaps, right?'   What makes you think this?  

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## 3 answers

### Answer by username_7 on 2022-10-03. Score: 7 | Accepted answer

While I believe this is a matter of semantics, in a meaningful, physical sense (with regards to quantum field theory) space is never really empty. Quantum fields exist everywhere, and particle pairs spontaneously come in and out of existence all the time, with effects that are measurable (e.g. vacuum polarization screening on particles). These fields fluctuate and correspond to the elementary particles that we are familiar with, such as neutrinos, photons, electrons, etc. they carry energy, and some have a vacuum expectation value that is non-zero.

Photons fill what would otherwise be considered ‘empty’ space as well, with at the very least the CMB being (almost) isotropically found.

In essence, while an area may not have macroscopic objects that you can see with the naked eye, I think one could comfortably say there has never been a ‘truly’ empty part of the universe, ever, because of the presence of these quantum fields.

> **Comments:**
> **username_5**: @username_0 This is a good answer, but note that good old atoms are still ubiquitous in space; see username_4's answer.  
> **username_0**: @username_5 Yes, I know. I meant about the space that filled in where there wasn’t any atoms.  

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### Answer by username_4 on 2022-10-03. Score: 9

No. Space isn't empty. There are atoms. The density varies quite a lot, from a million atoms per cubic centimeter to fewer than one per 100000 cm³. Mostly this is in the form of hydrogen.

And there are photons, neutrinos, dark matter (whatever that is), electromagnetic field...

Moreover on a larger scale there are particles of dust, and of course at an even larger scale, there are stars and planets in space.

Space is much more empty than the atmosphere, but it isn't completely empty.

> **Comments:**
> **username_5**: +1, but note that 10,000 cm⁻³ is _dense_ in astrophysics!  
> **username_5**: Ah, sorry, I read it as "10,000 per cm$^3$". You're right, one per 10,000 cm$^3$ is not dense (although still an order of magnitude denser than the average density).  

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### Answer by username_6 on 2022-10-03. Score: -3

Well there is radiation from CMB, maybe near a galixy a magnetic field, you have virtual particles, here is an interesting video


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