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Questions tagged [observable-universe]

Questions regarding the region of space containing all the objects that we can detect using any method of observation.

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Would we know if the universe was rotating?

I was wondering what we would observe if the universe had a small rotation. My conclusion was that galaxies on the equatorial plane of the universe would be slightly more redshifted than galaxies than ...
KDP's user avatar
  • 373
11 votes
1 answer
1k views

How many individual extrasolar "shiny" objects has humanity identified?

Sorry, if this is a 'stupid' question of a non-expert, but this question came recently up in family discussion of mine and I couldn't give a satisfactory answer: I know we have good (?) estimates of ...
BmyGuest's user avatar
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-2 votes
1 answer
167 views

Why no Big Bang are happening now?

Why we are not able to see any Big Bang now? There is a possibility, I think. Is it that Universe is so large that the probability of it's happening in the observable universe is almost zero, or is ...
KeShAw's user avatar
  • 21
0 votes
0 answers
87 views

How can the universe be 13 billion years old, but objects are seen farther away than that? [duplicate]

I keep running into this paradox, and the answers I get seem to be the same and not satisfying. Most sites say the universe is about 13 billion years old, but we can see objects farther away, like 50 ...
eSurfsnake's user avatar
5 votes
1 answer
796 views

Is there any way to detect the three-dimensional distribution of baryonic gas in our Universe?

As the title suggests, can the current observational techniques detect the 3D large-scale distribution of the baryonic gas, rather than just the gas within groups or clusters?
Wang Yun's user avatar
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13 votes
1 answer
2k views

As of now how much larger is our practically observable universe compared to just prior to JWST becoming operational

On April 2 2022 I asked for estimates of expected results. How much larger will the "observable by us" universe be when JWST becomes operational?. As of Jan 27 2024 with JWST operational for ...
BradV's user avatar
  • 767
4 votes
2 answers
345 views

Was the Big Bang an event within a preexisting Universe, or did it mark the beginning of the entire Universe, beyond just the observable Universe?

Could it be that the Universe is truly infinite, and the Big Bang was merely a singular, specific event that resulted in the birth of a 'bubble,' i.e. what we perceive as 'the observable universe'? ...
impact's user avatar
  • 51
0 votes
1 answer
50 views

Formula for rate of expansion of the universe vs distance?

How does the distance $r$ scale with the expansion of the universe?For example if $r_{o}$ is the distance between us and a galaxy and $V(r_{o})$ is the rate of expansion of the universe at that ...
Root's user avatar
  • 21
21 votes
3 answers
6k views

How can telescopes see anything at all?

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 ...
Victor Debone's user avatar
0 votes
1 answer
118 views

Is the universe still considered "finite but unbounded"?

The BBC reports in Alien life in Universe: Scientists say finding it is 'only a matter of time' that Scotland's Astronomer Royal, Catherine Heymans, has said We live in an infinite Universe, with ...
Mark Morgan Lloyd's user avatar
6 votes
1 answer
151 views

What natural astronomical object is rare on a Hubble volume scale?

There are some milestone objects on different scales of the universe. The star is a notable feature on a solar system scale The supermassive black hole is a feature on a scale of a galaxy ?? The ...
FrogOfJuly's user avatar
1 vote
0 answers
42 views

Has any astronomer/physicist used geometry and trigonometry to calculate where the center of the universe is? [duplicate]

Since we are pretty sure that the universe is expanding at a steady and accelerating rate wouldn’t it be possible to simultaneously observe 4 points (galaxies) that are all, as closely as we can tell, ...
Nivek Oheg's user avatar
1 vote
0 answers
74 views

What Parts of the Observable Universe have we Observed?

Everyone talks about how big the observable universe is, all of the complexity, etc... But what parts of the observable universe have we actually seen? What Parts are hidden in relative shadows? Is ...
skout's user avatar
  • 309
1 vote
0 answers
62 views

Can the gravity of objects entering the observable universe be detected?

As time passes, we will be able to see objects that are further away, as their light eventually reaches us. Since gravity also travels at the speed of light, would we be able to detect when a super ...
Colin's user avatar
  • 79
3 votes
3 answers
1k views

Could the redshift of all incoming photons be explained by a massive ring of distant masses pulling the sources of the photons away?

ChatGPT and wikipedia have informed me that the primary evidence for the theory that the universe is expanding is the fact that photons that arrive to our planet from all directions are being ...
Hisham's user avatar
  • 231
1 vote
1 answer
709 views

What is the rarest stable element in the universe? [closed]

I am making a hard sci-fi game with a focus on realism, in this game there is a need for a hard element to base money off of. Similar to how gold is used on earth. I know there are lots of elements ...
Dylan Bozarth's user avatar
0 votes
0 answers
170 views

where are we in the universe as compared to the observable universe? [duplicate]

For distant galaxies to be accelerating away at equal speed in every direction, Earth would have to be at the centre of the universe. Since it is not, some region of the distant galaxies should appear ...
Clifford Lingwood's user avatar
3 votes
1 answer
260 views

Conditions in the Early Universe

I am interested in how the large-scale properties of the Universe change over time. Does anyone know a trusted website which gives the temperature, density and radius (distance to the particle horizon)...
John Davies's user avatar
5 votes
2 answers
339 views

Size of the whole universe if it were spherical

Suppose the universe is spherical and its density ratio is $\Omega \leq 1.00125$ $\Omega = 1.00125$ is approximately the maximum possible value of the density ratio according to the Planck Mission ...
Albert's user avatar
  • 2,182
1 vote
1 answer
71 views

Other Hubble spheres with no Lorentz symmetry?

Perhaps this may be a stupid question but anyways here it goes... If the Lorentz symmetry is not global but rather local, wouldn't that mean that is possible that other Hubble spheres outside our ...
vengaq's user avatar
  • 1,017
3 votes
0 answers
120 views

When Only 50% percent of the sky will be filled with stars?

Answers to Approximately what percent of the sky has nothing in it? seem to suggest that with enough depth, we will finally hit something hence the sky is basically 100% full for any given resolution. ...
d_e's user avatar
  • 1,667
20 votes
5 answers
4k views

Approximately what percent of the sky has nothing in it?

From my persepective here on Earth, the sky seems to look like a few large-ish things and a bunch of tiny things. Hubble teaches us that even the apparent void between the tiny things has many very ...
Him's user avatar
  • 337
2 votes
1 answer
408 views

Would an observer standing at the edge of the "observable universe" perceive the expansion of space-time?

I got this bizarre idea in my mind, after reading SCP-3321 There, as a person gets teleported through a wormhole, ends up at the edge of the Observable Universe, 46 billion light-years away from Earth....
Alastor's user avatar
  • 2,668
3 votes
0 answers
89 views

Are there any binary red supergiants?

I wonder if we ever have identified or observed a pair of binary stars (red supergiants). And I also wonder what would happen if they exploded, (theoretically) as we haven’t observed it. Also, would ...
schrodingerscat's user avatar
3 votes
0 answers
69 views

How do we know universe is expanding and not light slowing down? [duplicate]

We tend to take some things for granted, for example the light of speed is constant, but what if it isn't? How can we know that light is not slowing down at great distances for example, or that light ...
Dimitris's user avatar
10 votes
3 answers
8k views

Is there anything currently 46 billion light years away from Earth that we can see?

If the oldest galaxy ever discovered, i.e GLASS-z13, is at a present proper distance of around 33 billion ly from Earth, why then do we define the observable universe to have a radius of around 46 ...
William's user avatar
  • 657
5 votes
1 answer
399 views

Does "Angular Diameter Turnaround Point" solve the Great Wall Problem?

According to Wikipedia, The Hercules–Corona Borealis Great Wall is the largest known structure in the observable universe, measuring approximately 10 billion light-years in length. But since it's ...
Monster196883's user avatar
24 votes
2 answers
5k views

How much larger will the "observable by us" universe be when JWST becomes operational?

Right now, using all our various current means of observing, we can "see" a sphere of X diameter around us. Webb will increase that to Y diameter. So our observable volume will increase by ...
BradV's user avatar
  • 767
-2 votes
1 answer
105 views

Is the solar system the only survivor of cosmic evolution? [closed]

A question has entered my mind, we know that all the phenomena in the universe are several thousand light years away from us, so the light we see from them is related to the past few years, now my ...
kiumars khaleghi's user avatar
8 votes
1 answer
226 views

How is observable matter distributed in the universe?

The observable matter in the universe is distributed and arranged into various structures, including black holes, stars, nebulae, and the much more diffuse regions of the inter-stellar and inter-...
YiFan's user avatar
  • 558
6 votes
1 answer
296 views

Can we consider the Universe to be some kind of 3-sphere?

This is probably a naive question. I'm learning a bit of cosmology and I've recently covered the so called angular size-redshift relation, which states that in an expanding Universe the angular size ...
Swike's user avatar
  • 3,926
2 votes
2 answers
145 views

How can the JWST telescope detect matter “shortly” after the big bang?

Since space is expanding, and accelerating, with distant locations accelerating at such a high rate that they are receding at greater than the speed of light, how can the Webb detect these distant ...
Gabe's user avatar
  • 29
0 votes
1 answer
145 views

If the ratio of actual total mass to critical mass (Ω) in the universe is only about 0.3, why do cosmologists believe it is flat, as far as we see?

What about astronomical observations makes scientists believe our universe is flat, at least as far as they can tell? Despite the critical Friedmann density being less than one, plus the existence of ...
Kurt Hikes's user avatar
  • 5,177
-2 votes
3 answers
313 views

If we could fly off edge of observable universe what would happen? [closed]

If we could be at the edge of expanding universe in a fast space ship such that we could go beyond the edge, what does the science think we might experience? Would we still be floating in space? Would ...
clearlight's user avatar
1 vote
0 answers
49 views

Can we observe galaxies after their recession velocity exceeds the speed of light? [duplicate]

It doesn't make sense to me that light could ever reach us from a galaxy moving away from us faster than the speed of light. But this video says that it can happen. Is this true? Could someone ...
Connor Garcia's user avatar
  • 16.3k
4 votes
6 answers
6k views

Logically, how can the universe be infinite in size?

Many people have told me that the “universe doesn’t care what you think” in my regards to it being infinite in size, and I know something that seems logical doesn’t mean anything when measured by ...
Max's user avatar
  • 59
4 votes
2 answers
404 views

Can we estimate the number of stars which have died in the observable universe?

We know there are currently between 10^22 and 10^24 stars in the observable universe, but can we make an estimate of how many stars have died so far? Or, in other words, how many supernovæ have taken ...
user2906's user avatar
  • 141
2 votes
1 answer
450 views

Why would a quantity like the 'Hubble contrast' be squared, then have its square root taken?

From Sabine Hossenfelder's recent video, New Evidence AGAINST Standard Cosmology: And her source.... Figure 2. The variation with increasing void radius of the variance of the Hubble parameter, the ...
Kurt Hikes's user avatar
  • 5,177
0 votes
1 answer
153 views

What defines Universe's Boundary? [duplicate]

We consider Heliopause as our solar system's boundary, Galaxy has its own boundary, certain theories says that there can be lots of universes, only when we define a boundary we can distinguish a ...
Kavin Ishwaran's user avatar
1 vote
1 answer
75 views

Universe is a cluster of orbiting Galaxies?

Like planets orbiting stars, solar systems and other celestial objects orbiting a blackhole in the center of a galaxy, are the Galaxies and Galaxy clusters orbiting the centre of a universe (for ...
Kavin Ishwaran's user avatar
4 votes
1 answer
323 views

Is quasar 2M1310-1714 outside the observable universe?

This Einstein ring Image credit: NASA / ESA / Hubble / T. Treu / Judy Schmidt shows multiple images of the quasar 2M1310-1714. Its distance is quoted at 17 billion light years and although the age ...
Dave Gremlin's user avatar
  • 1,071
9 votes
1 answer
279 views

How distant were the furthest currently-observable cosmic events when their currently-observed radiation was emitted?

(Edited for clarity. Thanks to James K and Connor Garcia.) This question about the most distant, observable cosmic objects made me wonder if we know the distance that was between us and them at the ...
Glycoversi's user avatar
6 votes
2 answers
184 views

How does the hypothesis of the "inconstant Hubble constant" solve the current crisis in cosmology?

It was published in a paper more or less like two months ago. I'd like to know also if more accurate measurements are necessary to close the gap between the model of the universe and the data reported....
bestofthebeast's user avatar
0 votes
0 answers
152 views

Volume of the observable universe [duplicate]

What about the volume of the observable universe? Can we find it? And what is the result in cubic light years?
Panagiotis Makris's user avatar
4 votes
2 answers
394 views

Is it "nonsense to even talk about" objects outside the observable universe not having gravitational influence on us? (finite speed of gravity)

In this supplemental answer to Is the zero gravity experienced in ISS the “artificial” kind? in Space Exploration SE I said: Gravity moves at the speed of light so nothing outside out observable ...
uhoh's user avatar
  • 31.1k
2 votes
0 answers
54 views

What are the one-dimensional observables that can reveal the matter clustering properties of the Universe?

As we all know, the distribution of galaxies, which depend on the spatial coordinates, can help us understand the large-scale structure of the Universe. We can measure the distribution of galaxies ...
Wang Yun's user avatar
  • 431
5 votes
1 answer
350 views

If we watched extremely red-shifted galaxies near the edge of the observable universe for a very long time, how would they change? Would more appear?

I have understanding sphere eversion as #1 on my bucket list (if I ever get a round tuit) but understanding metric expansion seems to be a rapidly receding possibility :-) Question: Suppose it takes ...
uhoh's user avatar
  • 31.1k
1 vote
0 answers
65 views

Can the other side of the observable universe be seen as a black hole?

When looking at the objects near the horizon of the observable universe, the objects seem to emit radiation that is red-shifted. Time seems to advance at a slower rate than our own and at the horizon ...
Deschele Schilder's user avatar
1 vote
3 answers
606 views

Is the dark matter just regular matter out of the observable universe?

Could it be that darkmatter is actually the gravitational influence of regular matter that is situated out of the observable universe?
sir_pi's user avatar
  • 11
2 votes
0 answers
96 views

How many galaxies are predicted in the observable universe? Does it contain dwarfs? Is there any size-ratio diagram?

According to quite recent research the observable universe contains about 2 trillion galaxies ($2 \cdot 10^{12}$). But what is counted there? Does this number also contain dwarf galaxies? According to ...
J. Doe's user avatar
  • 245