Starship Asterisk*

The Observable Universe

Explanation: How far can you see? Everything you can see, and everything you could possibly see, right now, assuming your eyes could detect all types of radiations around you -- is the observable universe. In light, the farthest we can see comes from the cosmic microwave background, a time 13.8 billion years ago when the universe was opaque like thick fog. Some neutrinos and gravitational waves that surround us come from even farther out, but humanity does not yet have the technology to detect them. The featured image illustrates the observable universe on an increasingly compact scale, with the Earth and Sun at the center surrounded by our Solar System, nearby stars, nearby galaxies, distant galaxies, filaments of early matter, and the cosmic microwave background. Cosmologists typically assume that our observable universe is just the nearby part of a greater entity known as "the universe" where the same physics applies. However, there are several lines of popular but speculative reasoning that assert that even our universe is part of a greater multiverse where either different physical constants occur, different physical laws apply, higher dimensions operate, or slightly different-by-chance versions of our standard universe exist.

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APOD Robot wrote: ↑Wed Mar 16, 2022 4:06 am Explanation: How far can you see? Everything you can see, and everything you could possibly see, right now, assuming your eyes could detect all types of radiations around you -- is the observable universe.

Not the observable universe, but an observable universe. Every observer in the Universe has their own observable universe, all different.

Chris Peterson wrote: ↑Wed Mar 16, 2022 4:37 am

APOD Robot wrote: ↑Wed Mar 16, 2022 4:06 am Explanation: How far can you see? Everything you can see, and everything you could possibly see, right now, assuming your eyes could detect all types of radiations around you -- is the observable universe.

Not the observable universe, but an observable universe. Every observer in the Universe has their own observable universe, all different.

Right. I saw a video the other day from "The Science Asylum", Is the Universe Infinite?. That video demonstrated the nature of our observable Universe very neatly:


Start at 1.53 if you want to see how "our past light cone" works. I thought that was a great illustration of what our observable Universe is.

Ann

Ann wrote: ↑Wed Mar 16, 2022 5:06 am
Right. I saw a video the other day from "The Science Asylum", Is the Universe Infinite?. That video demonstrated the nature of our observable Universe very neatly: Start at 1.53 if you want to see how "our past light cone" works. I thought that was a great illustration of what our observable Universe is.

Very cool concept!
That's the direct link to that point in the video:
https://youtu.be/fApKpDGGDYk?t=113

I really like this highly detailed APOD. I love the fact that so many stars and galaxies were annotated! All right, I found it borderline offensive that the blue stellar beacon of the north, Vega, is being shown as deeply orange! A few other blue stars are also shown as orange, like Algol and Altair, and tiny rather cool white dwarf Van Maanen's Star is shown as a bright blue star. But I can't really expect every star to be matched with its "true" color or luminosity when so many stars are being shown here!

I love all the galaxies, too. Here are a few "translations":

Bode's galaxy = M81

Sunflower galaxy = M63

Black Eye galaxy = M64

Whirlpool galaxy = M51

Pinwheel galaxy = M101

Sombrero galaxy = M104

NGC 7318, 7319 and 7320: Galaxies relating to Stephan's Quintet

Bird galaxy = ESO 593-8

Mice galaxies = NGC 4676

Arp 147 = IC 298

Cigar galaxy = M82

Mayall's Object = Arp 148

Tadpole galaxy = Arp 188

Hoag's Object = PGC 54559

Sculptor galaxy = NGC 253

Bubble galaxy = NGC 3521? Arp 220? Something else?

Eyes Galaxies = NGC 4435 and NGC 4438

Atoms for Peace galaxy = NGC 7252

Butterfly galaxies = NGC 4567 and NGC 4568

Sarah's galaxy = Hamburger galaxy

The Circinus galaxy = ESO 97-G13

Centaurus A = NGC 5128

Maffei 2 = PGC 10217

Footprint galaxy = UGC 8091

Phew! I'm done.

Ann

Beautiful work yet it also manages to make the universe seem rather creepy…

Eric

Well that may make the Heliocentrists happy, but also seems to big up the Geocentrists!
Copernicus may be either happy or sad, depending on which way he observes this.
John

JohnD wrote: ↑Wed Mar 16, 2022 11:51 am Well that may make the Heliocentrists happy, but also seems to big up the Geocentrists!
Copernicus may be either happy or sad, depending on which way he observes this.
John

We are not the center of the Universe. But we are, indeed, the center of our universe.

Our observable universe.

Ann

Ann wrote: ↑Wed Mar 16, 2022 12:32 pm

JohnD wrote: ↑Wed Mar 16, 2022 11:51 am Well that may make the Heliocentrists happy, but also seems to big up the Geocentrists!
Copernicus may be either happy or sad, depending on which way he observes this.
John

We are not the center of the Universe. But we are, indeed, the center of our universe.

Our observable universe.

Actually, there is good reason to believe that each of us exists at the geometric center of the entire universe, at least when we consider its three spatial dimensions.

Why does it seem that M66 is listed twice?

Oh My; mind bungling isn't it? My belief is that there is no end to the
universe! but who knows! Any way; what would there be at the end
of the universe? There would have to be more space, I would think!
???????????????????????????
Picture kind of reminds me of a virus image!

orin stepanek wrote: ↑Wed Mar 16, 2022 1:56 pm VisUni_WikiBudassi_2400.jpg
Oh My; mind bungling isn't it? My belief is that there is no end to the
universe! but who knows! Any way; what would there be at the end
of the universe? There would have to be more space, I would think!

To be clear, as this image might be misunderstood, it in no way suggests that there is any "end" or edge to the Universe.

Chris Peterson wrote: ↑Wed Mar 16, 2022 2:06 pm To be clear, as this image might be misunderstood, it in no way suggests that there is any "end" or edge to the Universe.

Indeed, Chris, which was my point above!

But I would not agree with your "Every observer in the Universe has their own observable universe, all different" which panders to the neoliberals and their negotiable 'truths'. Which may have a reality in politics but not in life, nor for goodness sake in science.
John

Chris Peterson wrote: ↑Wed Mar 16, 2022 2:06 pm

orin stepanek wrote: ↑Wed Mar 16, 2022 1:56 pm VisUni_WikiBudassi_2400.jpg
Oh My; mind bungling isn't it? My belief is that there is no end to the
universe! but who knows! Any way; what would there be at the end
of the universe? There would have to be more space, I would think!

To be clear, as this image might be misunderstood, it in no way suggests that there is any "end" or edge to the Universe.

Thanks Chris! I wasn't trying to mislead anyone! Just my own Idea on beyond what we can see!

JohnD wrote: ↑Wed Mar 16, 2022 2:33 pm

Chris Peterson wrote: ↑Wed Mar 16, 2022 2:06 pm To be clear, as this image might be misunderstood, it in no way suggests that there is any "end" or edge to the Universe.

Indeed, Chris, which was my point above!

But I would not agree with your "Every observer in the Universe has their own observable universe, all different" which panders to the neoliberals and their negotiable 'truths'. Which may have a reality in politics but not in life, nor for goodness sake in science.
John

What? That we are each at the center of a unique and different observable universe is a simple fact. There is no alternative explanation. An observable universe is defined by a sphere of a certain radius around a 3D point. There are an infinite number of such center points in the Universe. The apparent edge of the universe I see is different from the apparent edge of the one you see.

(Whether we are all at our own centers of the Universe as a whole depends upon how we define "center" and on the topology of the Universe.)

Actually there is more universe than i will ever need!

This is a fantastic APOD. Thank you also for all the comments. I have often wondered about the phraseology used to define the limits of our universe. This makes it more reasonable that our "observable" universe is 13.4 billion years old rather than "the" universe is 13.4 billion years old. This should indicate as our technical skills increase, the age and size of our "observable" universe may also increase leading to the necessity of rewriting our science books!

NCTom wrote: ↑Wed Mar 16, 2022 2:56 pm This is a fantastic APOD. Thank you also for all the comments. I have often wondered about the phraseology used to define the limits of our universe. This makes it more reasonable that our "observable" universe is 13.4 billion years old rather than "the" universe is 13.4 billion years old. This should indicate as our technical skills increase, the age and size of our "observable" universe may also increase leading to the necessity of rewriting our science books!

No. The entire universe is 13.4 billion years old (most recent analysis: 13.8 billion years old). The observable universe is no younger.

Chris Peterson wrote: ↑Wed Mar 16, 2022 4:37 am

APOD Robot wrote: ↑Wed Mar 16, 2022 4:06 am Explanation: How far can you see? Everything you can see, and everything you could possibly see, right now, assuming your eyes could detect all types of radiations around you -- is the observable universe.

Not the observable universe, but an observable universe. Every observer in the Universe has their own observable universe, all different.

Valid point. But right now, my observable universe is bounded by the walls of a small office. So, we could define, for the sake of convenience in conversation, the union over the set of all humans currently alive, of the portion of space that any of them will be able to observe over the next year or so. And then we could call that the observable universe, which I would consider a useful notion. This would automatically cover the question of different types of signals, because it would include our use of Hubble, JWST, LIGO, Chandra, etc.

(Still many philosophical issues remain with my definition. For one, we don't observe space, but we observe signals that have come to us. And so we're talking about points in space that we are surmising to be the points of origin of the signals. And then that's still rather complicated, given current cosmological views of the history of things in that observable universe.)

NCTom wrote: ↑Wed Mar 16, 2022 2:56 pm This is a fantastic APOD. Thank you also for all the comments. I have often wondered about the phraseology used to define the limits of our universe. This makes it more reasonable that our "observable" universe is 13.4 billion years old rather than "the" universe is 13.4 billion years old. This should indicate as our technical skills increase, the age and size of our "observable" universe may also increase leading to the necessity of rewriting our science books!

I wholeheartedly agree! And I'm placing my bet that the James Webb Telescope (JWST) is going to observe some things that puncture our current view of how things are. I don't know if it's possible, but if it images a highly red-shifted galaxy that figures to be 20 billion years old, that'll be a great moment.

MarkBour wrote: ↑Wed Mar 16, 2022 3:48 pm

NCTom wrote: ↑Wed Mar 16, 2022 2:56 pm This is a fantastic APOD. Thank you also for all the comments. I have often wondered about the phraseology used to define the limits of our universe. This makes it more reasonable that our "observable" universe is 13.4 billion years old rather than "the" universe is 13.4 billion years old. This should indicate as our technical skills increase, the age and size of our "observable" universe may also increase leading to the necessity of rewriting our science books!

I wholeheartedly agree! And I'm placing my bet that the James Webb Telescope (JWST) is going to observe some things that puncture our current view of how things are. I don't know if it's possible, but if it images a highly red-shifted galaxy that figures to be 20 billion years old, that'll be a great moment.

That's not really possible. Anything we observe has to have a redshift less than that of the CMB, which marks the edge of what is observable at all with electromagnetic radiation, regardless of the technology used.

The CMB redshift is z = 1100, which corresponds to a light travel time of 13.7 billion years.

It is unlikely that JWST will alter our understanding of the age of the Universe. It very likely will allow us to refine our understanding of the evolution of the Universe, however, by letting us see how galaxies (and maybe even stars) were forming very early on.

Is our universe just an unfolding version of its earlier self? Are we existing in dimensions 7-8-9 but can’t physically access the others?

If so, I still contemplate size and time as being the same thing. By the way, where’s Art in the big picture

I think it is funny and very narcissistic that we are always placed in the center of the universe. How do we know we are not at an "edge"?

Guest wrote: ↑Wed Mar 16, 2022 4:39 pm I think it is funny and very narcissistic that we are always placed in the center of the universe. How do we know we are not at an "edge"?

Because there is no edge.

Guest wrote: ↑Wed Mar 16, 2022 1:41 pm Why does it seem that M66 is listed twice?

Good point. Because the artist behind the image likes it so much? M66

(Or he got distracted - darn, I forgot to buy milk, and I bet I didn't include M66 among the galaxies in my picture of the observable Universe - better fix that right away...)

Ann