<blockquote>
<p>Does that mean that between those 7,000 light-years, there's absolute nothing in the way that obscures the pillars? Given it's arcseconds, I'd expect that any kind of disturbance would make it simply impossible to visualize it.</p>
</blockquote>
<p>Almost, with a few details.</p>
<p>It means there's nothing <em>opaque</em> in the way. At risk of being trite, the telescope lens and the atmosphere (well, not for Hubble) is often &quot;in the way&quot;, but they're transparent. Many substances are opaque only in some wavelengths and transparent in others. Astronomical photographs are sometimes not literally what you would see with your eye, they are false-color.</p>
<p>While it may seem amazing that no object happens to be in a 7k lyr cone, keep in mind that's not the &quot;experiment&quot;. It is actually an infinitely long cone and we see only the first object. For example, there could be an object directly behind Proxima Centauri, and we wouldn't see it. So the true &quot;property&quot; is the distribution of distances to the <em>foremost</em> object in each cone coming out of the telescope. This distribution is generally as you would expect given the number, size and type of objects you find in the universe.</p>
<p>Of course if there was actually an object behind Proxima Centauri, we could still detect it as it moves around (and we do) - it would eventually &quot;peek out&quot;. Incidentally, other planets, the Moon, the Earth, the Sun often obscure celestial bodies - but not all the time. But if by unlikely coincidence the obstacle's orbit was in perfect sync with the telescope and the obstacle, we might still be able to detect it due to <a href="https://en.wikipedia.org/wiki/Einstein_Cross" rel="noreferrer">gravity bending light around the obstacle</a>.</p>
<p>So in sum:</p>
<ul>
<li>Not every obstacle blocks every wavelength</li>
<li>Most objects (including us) are moving so they are not always <em>permanently</em> obscured</li>
<li>Even objects that are truly obscured can still be observed indirectly</li>
<li>Objects that are truly obscured are unknown to us, therefore you can't rightly marvel at how few of them there are, since you don't rightly know if there's few or many</li>
</ul>

CC BY-SA 4.0
2023-10-11T15:53:06.893Z
Still, if there are many, we would see something in every direction. That is obviously not true. That is Olbers' paradox, and shows that the universe is finite in space and has a finite age, and stars don't live forever
planetmaker
CC BY-SA 4.0
2023-10-11T16:33:57.663Z
@planetmaker if there are many obscured? That's not obvious. In fact our [deep scans](https://en.wikipedia.org/wiki/Hubble_Deep_Field) show that looking at the darkest parts of the sky long enough will show you entire galaxies that are distant and dim. Such galaxies could easily be hiding behind most visible stars. While the universe is sparse, the sky is packed.
candied_orange
CC BY-SA 4.0
2023-10-11T18:28:39.830Z
@candied_orange if every sightline ended on a star, the sky would be as bright as the surface of a star.
ProfRob
CC BY-SA 4.0
2023-10-11T18:34:48.107Z
@ProfRob technically true but only because the surface of a star comes in many different brightness's. Black sky is not the same as an empty sky.
candied_orange
CC BY-SA 4.0
2023-10-11T18:48:38.520Z
@ProfRob And while I didn't claim that every sightline ended on a star, one could argue that every site line ends at the big bang.
candied_orange
CC BY-SA 4.0
2023-10-12T02:42:46.060Z
@ProfRob what units are you using?
candied_orange
CC BY-SA 4.0
2023-10-12T04:21:12.227Z
@candied_orange z as a measurement of redshift is pretty much just a multiplier, doesn’t really have any units
Topcode
CC BY-SA 4.0
2023-10-12T08:14:25.157Z
Almost all sightlines end at redshift z=1100.
ProfRob
CC BY-SA 4.0
2023-10-12T13:19:20.430Z
Redshift affects the light. Not the line. Which only further supports the idea that black != empty.
candied_orange
CC BY-SA 4.0
2023-10-12T13:39:07.623Z
The large telescopes needed for such images are not build with lenses of that diameter, mirrors are used instead, sometimes together with a small corrective lens.
Uwe
CC BY-SA 4.0
2023-10-13T07:00:27.437Z
See https://astronomy.stackexchange.com/a/55013/2531 @candied_orange
ProfRob
CC BY-SA 4.0
2023-10-11T15:03:09.240Z
2023-10-11T15:08:58.307Z
2023-10-11T15:08:58.307Z
gomennathan
<p>I can't speak to the creation of a photo of Pillars of Creation specifically, but in general:</p>
<blockquote>
<p>I'd expect that any kind of disturbance would make it simply impossible to visualize it.</p>
</blockquote>
<p>Your question is built on the assumption that an image is taken as a single complete snapshot. It isn't, usually because of the kinds of perturbations that you're referencing.</p>
<p>Think of it as if I cut out a 10cm circle in a large piece of cardboard, I put it over a painting, and I move it around. You never see the painting in its entirety, but if you keep looking and combine your individual observations, you will be able to reconstruct the full painting (assuming that I've shown you all the parts of the painting at some point in time).</p>
<p>You could never use your camera to photograph the entire painting in a single go, but you could take many photos and stitch them together in order to form an aggregate image.</p>
<p>So yes, while you might not get the full image simultaneously, with a long enough exposure time you will be able to reconstruct it with enough visual fidelity for what the average human expects.</p>

CC BY-SA 4.0
2023-10-13T15:54:41.730Z
This doesn't really address what the question is asking. Whether the image is taken as a single short exposure or a mosaic of small long-exposure images makes essentially no difference for the significance of any hypothetical objects obscuring the line of sight somewhere in the middle of the 7k lyr void. Unless it's very small or impossibly fast or you're thinking of exposure times in the millions of years, it'll obscure the sight the whole time the same way.
leftaroundabout
CC BY-SA 4.0
2023-10-13T23:43:18.983Z
@leftaroundabout: The third paragraph asks a different question than the fourth paragraph. I'm answering the question in the third paragraph.
Flater
CC BY-SA 4.0
2023-10-13T04:19:36.673Z
2023-10-13T04:19:36.673Z
Flater
<p>Yes, space is very empty. There is not nothing between us an the Eagle nebula, but little enough that we can still get a reasonable view of it.</p>
<p>The pillars are ephemeral, they are evolving on timescales that, whilst slow on human timescales, are quite rapid on the timescales of galactic evolution. There probably won't be much evidence of them in a few million years.</p>
<p>The pillars do &quot;hide&quot; a portion of space behind them (and inside them). This is why you often see observations taken at infrared wavelengths because light at this wavelength can penetrate the gas and (mainly) dust making up the pillars more easily than visible wavelengths and we can see into them and behind them. See <a href="https://www.esa.int/ESA_Multimedia/Images/2022/10/Hubble_and_Webb_showcase_the_Pillars_of_Creation_side_by_side" rel="noreferrer">here for example</a>.</p>

CC BY-SA 4.0
2023-10-11T13:17:27.507Z
On the last paragraph, https://www.esa.int/ESA_Multimedia/Images/2022/10/Hubble_and_Webb_showcase_the_Pillars_of_Creation_side_by_side is useful -- It shows the difference between Hubble's (visible) and Webb's (infrared) view of the pillars.
R.M.
CC BY-SA 4.0
2023-10-10T16:22:20.583Z
2023-10-11T13:35:33.253Z
2023-10-11T13:35:33.253Z
ProfRob
<p>I'm impressed that we have any telescope imagery at all. Take the images we have from the &quot;Pillars of Creation&quot;.</p>
<p>The Pillars of Creation is in the Eagle Nebula, some 7,000 light-years away from Earth. It's estimated its size is about 4 light years.</p>
<p>Does that mean that between those 7,000 light-years, there's absolute nothing in the way that obscures the pillars? Given its arcseconds, I'd expect that any kind of disturbance would make it simply impossible to visualize it.</p>
<p>Also, does that also means that the pillars occupy that portion (albeit minuscule) of the sky permanently? What I wonder is, what is behind the ever growing portion of the sky being hidden by those 4 light years of size?</p>

CC BY-SA 4.0
2023-10-10T15:50:22.730Z
Mostly yes. Space is large and empty
planetmaker
CC BY-SA 4.0
2023-10-10T15:54:34.613Z
Cue Hitchhikers Guide to the Galaxy…
Jon Custer
CC BY-SA 4.0
2023-10-10T19:04:30.910Z
The fact that space objects block the things behind them is one of the difficulties of viewing our own galaxy -- you can't see the center of the Milky Way very well because it's so dense with stars and dust that it blocks the view of whatever is behind it.
Darth Pseudonym
CC BY-SA 4.0
2023-10-11T07:28:41.680Z
https://www.youtube.com/watch?v=DrStUegqTkU
Leos Ondra
CC BY-SA 4.0
2023-10-11T18:33:20.600Z
The pillars are the thing obstructing the view the objects behind them.
Lamar Latrell
CC BY-SA 4.0
2023-10-11T20:56:19.897Z
That's a testament to how empty and big space is. That's why it's called space. ;)
DKNguyen
CC BY-SA 4.0
2023-10-12T16:10:38.687Z
Yes, this is why we call it "Space".
RBarryYoung
CC BY-SA 4.0
2023-10-12T18:40:23.540Z
@JonCuster For those who don't get the reference, or just want to enjoy it again: https://youtu.be/Hv1spjsvu-A?t=7
gidds
CC BY-SA 4.0
2023-10-13T01:35:43.073Z
Or *"[Space, it says, is big, really big.](https://www.youtube.com/watch?v=Dwz3XLVxXac&list=PLSoD2CcPrumFUOPyA8aLONTz5jr-IQFu5&index=9&t=0m19s)"*
Peter Mortensen
CC BY-SA 4.0
2023-10-16T22:20:07.957Z
It doesn't at mean there's absolute nothing in the way that obscures the pillars… merely that there's not enough in the way to matter.

That there's not enough in the way matters only at current resolutions. Seeing through the same obstructions might need nothing but better optics and either way other considerations such as infra-red, ultra-violet and what have might huge differences.
Robbie Goodwin
<telescope><observable-universe>
How can telescopes see anything at all?
Victor Debone
# How can telescopes see anything at all?

(Asked by: username_0 on 2023-10-10)

I'm impressed that we have any telescope imagery at all. Take the images we have from the "Pillars of Creation".

The Pillars of Creation is in the Eagle Nebula, some 7,000 light-years away from Earth. It's estimated its size is about 4 light years.

Does that mean that between those 7,000 light-years, there's absolute nothing in the way that obscures the pillars? Given its arcseconds, I'd expect that any kind of disturbance would make it simply impossible to visualize it.

Also, does that also means that the pillars occupy that portion (albeit minuscule) of the sky permanently? What I wonder is, what is behind the ever growing portion of the sky being hidden by those 4 light years of size?

**Tags:** telescope, observable-universe
> **Comments:**
> **username_1**: Mostly yes. Space is large and empty  
> **username_2**: Cue Hitchhikers Guide to the Galaxy…  
> **username_3**: The fact that space objects block the things behind them is one of the difficulties of viewing our own galaxy -- you can't see the center of the Milky Way very well because it's so dense with stars and dust that it blocks the view of whatever is behind it.  
> **username_4**: https://www.youtube.com/watch?v=DrStUegqTkU  
> **username_5**: The pillars are the thing obstructing the view the objects behind them.  
> **username_6**: That's a testament to how empty and big space is. That's why it's called space. ;)  
> **username_7**: Yes, this is why we call it "Space".  
> **username_8**: @JonCuster For those who don't get the reference, or just want to enjoy it again: https://youtu.be/Hv1spjsvu-A?t=7  
> **username_9**: Or *"[Space, it says, is big, really big.](https://www.youtube.com/watch?v=Dwz3XLVxXac&list=PLSoD2CcPrumFUOPyA8aLONTz5jr-IQFu5&index=9&t=0m19s)"*  
> **username_10**: It doesn't at mean there's absolute nothing in the way that obscures the pillars… merely that there's not enough in the way to matter.  That there's not enough in the way matters only at current resolutions. Seeing through the same obstructions might need nothing but better optics and either way other considerations such as infra-red, ultra-violet and what have might huge differences.  

---

## 3 answers

### Answer by username_13 on 2023-10-10. Score: 49 | Accepted answer

Yes, space is very empty. There is not nothing between us an the Eagle nebula, but little enough that we can still get a reasonable view of it.

The pillars are ephemeral, they are evolving on timescales that, whilst slow on human timescales, are quite rapid on the timescales of galactic evolution. There probably won't be much evidence of them in a few million years.

The pillars do "hide" a portion of space behind them (and inside them). This is why you often see observations taken at infrared wavelengths because light at this wavelength can penetrate the gas and (mainly) dust making up the pillars more easily than visible wavelengths and we can see into them and behind them. See [here for example](https://www.esa.int/ESA_Multimedia/Images/2022/10/Hubble_and_Webb_showcase_the_Pillars_of_Creation_side_by_side).

> **Comments:**
> **username_18**: On the last paragraph, https://www.esa.int/ESA_Multimedia/Images/2022/10/Hubble_and_Webb_showcase_the_Pillars_of_Creation_side_by_side is useful -- It shows the difference between Hubble's (visible) and Webb's (infrared) view of the pillars.  

---

### Answer by username_11 on 2023-10-11. Score: 22

> Does that mean that between those 7,000 light-years, there's absolute nothing in the way that obscures the pillars? Given it's arcseconds, I'd expect that any kind of disturbance would make it simply impossible to visualize it.

Almost, with a few details.

It means there's nothing *opaque* in the way. At risk of being trite, the telescope lens and the atmosphere (well, not for Hubble) is often "in the way", but they're transparent. Many substances are opaque only in some wavelengths and transparent in others. Astronomical photographs are sometimes not literally what you would see with your eye, they are false-color.

While it may seem amazing that no object happens to be in a 7k lyr cone, keep in mind that's not the "experiment". It is actually an infinitely long cone and we see only the first object. For example, there could be an object directly behind Proxima Centauri, and we wouldn't see it. So the true "property" is the distribution of distances to the *foremost* object in each cone coming out of the telescope. This distribution is generally as you would expect given the number, size and type of objects you find in the universe.

Of course if there was actually an object behind Proxima Centauri, we could still detect it as it moves around (and we do) - it would eventually "peek out". Incidentally, other planets, the Moon, the Earth, the Sun often obscure celestial bodies - but not all the time. But if by unlikely coincidence the obstacle's orbit was in perfect sync with the telescope and the obstacle, we might still be able to detect it due to [gravity bending light around the obstacle](https://en.wikipedia.org/wiki/Einstein_Cross).

So in sum:

* Not every obstacle blocks every wavelength
* Most objects (including us) are moving so they are not always *permanently* obscured
* Even objects that are truly obscured can still be observed indirectly
* Objects that are truly obscured are unknown to us, therefore you can't rightly marvel at how few of them there are, since you don't rightly know if there's few or many

> **Comments:**
> **username_1**: Still, if there are many, we would see something in every direction. That is obviously not true. That is Olbers' paradox, and shows that the universe is finite in space and has a finite age, and stars don't live forever  
> **username_12**: @planetmaker if there are many obscured? That's not obvious. In fact our [deep scans](https://en.wikipedia.org/wiki/Hubble_Deep_Field) show that looking at the darkest parts of the sky long enough will show you entire galaxies that are distant and dim. Such galaxies could easily be hiding behind most visible stars. While the universe is sparse, the sky is packed.  
> **username_13**: @candied_orange if every sightline ended on a star, the sky would be as bright as the surface of a star.  
> **username_12**: @ProfRob technically true but only because the surface of a star comes in many different brightness's. Black sky is not the same as an empty sky.  
> **username_12**: @ProfRob And while I didn't claim that every sightline ended on a star, one could argue that every site line ends at the big bang.  
> **username_12**: @ProfRob what units are you using?  
> **username_14**: @candied_orange z as a measurement of redshift is pretty much just a multiplier, doesn’t really have any units  
> **username_13**: Almost all sightlines end at redshift z=1100.  
> **username_12**: Redshift affects the light. Not the line. Which only further supports the idea that black != empty.  
> **username_15**: The large telescopes needed for such images are not build with lenses of that diameter, mirrors are used instead, sometimes together with a small corrective lens.  
> **username_13**: See https://astronomy.stackexchange.com/a/55013/2531 @candied_orange  

---

### Answer by username_16 on 2023-10-13. Score: 1

I can't speak to the creation of a photo of Pillars of Creation specifically, but in general:

> I'd expect that any kind of disturbance would make it simply impossible to visualize it.

Your question is built on the assumption that an image is taken as a single complete snapshot. It isn't, usually because of the kinds of perturbations that you're referencing.

Think of it as if I cut out a 10cm circle in a large piece of cardboard, I put it over a painting, and I move it around. You never see the painting in its entirety, but if you keep looking and combine your individual observations, you will be able to reconstruct the full painting (assuming that I've shown you all the parts of the painting at some point in time).

You could never use your camera to photograph the entire painting in a single go, but you could take many photos and stitch them together in order to form an aggregate image.

So yes, while you might not get the full image simultaneously, with a long enough exposure time you will be able to reconstruct it with enough visual fidelity for what the average human expects.

> **Comments:**
> **username_17**: This doesn't really address what the question is asking. Whether the image is taken as a single short exposure or a mosaic of small long-exposure images makes essentially no difference for the significance of any hypothetical objects obscuring the line of sight somewhere in the middle of the 7k lyr void. Unless it's very small or impossibly fast or you're thinking of exposure times in the millions of years, it'll obscure the sight the whole time the same way.  
> **username_16**: @leftaroundabout: The third paragraph asks a different question than the fourth paragraph. I'm answering the question in the third paragraph.  

---

