Questions tagged [universe]

Questions regarding all of time and space and its contents.

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CMBR: Is the cold spot a hint at the edge of the universe?

Could the big cold spot in the CMBR map be a sign that almost all radiation from that direction has already passed us, and that be a sign that the end of the universe is closest to earth in that ...
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2 votes
0 answers
47 views

Is there a cosmological model of the evolution of vacuum motion in our universe over time? [closed]

Is there a cosmological model of the evolution of vacuum motion in our universe over time? Does this model starting from a non-vacuum constitute an advantage compared to the cosmological model of ...
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1 answer
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Determining the age and size of the Universe

Before we can determine the size of the Universe, do we not have to determine first if the Universe is infinite or finite because an infinite Universe would have no size ?
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5 votes
6 answers
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Interpretation of Hubble constant in SI units

The standard interpretation of Hubble constant $\approx 70~\text{km/s/Mpc}$ means that each mega-parsec of distance adds $70~\text{km/s}$ to a galaxy recession velocity from us (or to a space ...
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1 vote
1 answer
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Time & The Big Bang [duplicate]

What are the arguments against a perpetual universe, i.e. one that expands from a singularity, like we observe with ours, then suffers from terminal entropy, collapses back upon itself before reaching ...
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5 votes
1 answer
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Is an extreme precession on a tidally locked planet possible?

Let's assume an exoplanet orbits a red dwarf star closely enough that is tidally locked to it. Is it possible for the planet to have a significant axial precession? If not naturally, is it possible to ...
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2 votes
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If a false-vacuum event occurred, would we be able to detect it?

Ever since I read about false vacuum decay a few years ago, I've always been having thoughts about whether or not it would be detectable (the end is near!). As the vacuum bubble propagates at the ...
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1 vote
0 answers
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Can the Universe itself be a black hole? [duplicate]

Can the Universe be a Black Hole? Many years ago, after reading a book by Isaac Asimov (not a novel, but I forgot the title) I started wondering if it is be possible that the Universe itself is a ...
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Heaviest star in universe

Using the estimated age of the universe, can we calculate the heaviest star in the universe using normal fusion reaction rate of our sun? Assuming the star did not die.
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Is the number of galaxies in the observable universe increasing? [duplicate]

Is the number of galaxies in the observable universe increasing? Are more and more galaxies coming into view? Or is the number decreasing? If it's increasing then when will it reach a maximum? If it's ...
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0 votes
1 answer
112 views

Can magnetic monopoles only exist in a curved universe? [closed]

I’m trying to figure out rules for my Sci-fi universe and I need to know what type of universe, the universe needs to be for the existence of magnetic monopoles to exist. I read somewhere that the ...
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6 answers
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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 ...
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15 votes
5 answers
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Will there be collision between universes?

I just watched one of those videos that shows the scale of the universe, zooming out from one thing all the way out to the sphere that is thought to be the universe. However, they also showed other ...
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Question re distribution of the baryonic matter in the Universe

In https://phys.org/news/2021-09-universe.html it says:"Scientists thus discovered some of the universe's missing baryons, thereby confirming that 80–90% of normal matter is located outside of ...
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What is the concept of wormholes? [duplicate]

My main queries for now I guess: What is the theory behind wormholes? What is the possibility and likeliness of their existence based on scientific analysis, not conspiracy theories? What is the ...
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-1 votes
1 answer
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is there any excuse or reason why our bubble in Hawking's space-time foam theory is retained? [closed]

Hawking said that universes are like bubbles that pop into existence and pop back into the vacuum some form then immediately pop, he calls this space-time foam, our bubble doesn't seem to pop ...
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What is the distance between solar system and a distant galaxy

When we say a galaxy is 300 million light-years away, is that its distance now or 300 million years ago?
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1 vote
1 answer
116 views

Because the Universe is expanding, what is it taking up?

It is my understanding that the universe is expanding and that matter takes up space. While the universe only contains small percent of matter, wouldn't expansion indicate that the universe is ...
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9 votes
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Are there only $10^{83}$ atoms in the universe?

I'm a high school junior. I assumed there would be an incredibly huge number of atoms in the universe if not infinite. Recently, I've come across a few articles which claim that scientists believe ...
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1 answer
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Scalar field displacement from the minimum of the potential gives rise to particles/dark matter, why?

The paper Lyman-alpha Constraints on Ultralight Scalar Dark Matter by Kobayashi et al. says, at the beginning of Section 3.1: A light scalar field stays frozen at its initial field value in the early ...
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2 votes
1 answer
54 views

FLWR and curvature

The FLWR metric or model I believe results from Einstein's equations of general relativity if it is assumed the universe is 1. homogeneous and 2. able to expand (or contract). Solutions can have ...
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1 vote
1 answer
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Can two neighboring galaxies move apart at steady speed?

While I was trying to understand the three models that obey Friedmann's two assumptions of a non-static universe, I came across a line that says and I quote "It (referring to Big Bang) starts at ...
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0 votes
1 answer
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Traversing a proton within the Planck time

If I could travel a super small distance (proton) in an even smaller time (Planck time), how long would it take me to cross the observable universe?
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3 votes
1 answer
111 views

What do falsifiability and verifiability actually mean as a precondition of a scientific hypothesis?

What do falsifiability and verifiability actually mean as a precondition of a scientific hypothesis? I have been hearing from science guys that unlike philosophical hypothesis or theory, to be a ...
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3 votes
3 answers
220 views

Density of stars on celestial sphere

The pattern of stars on the surface of the celestial sphere seems perceptually to have an universally looking structure. If you pick a region of the sky at random, for instance by using the (excellent)...
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if the universe is infinite shouldn't it have experienced an infinite number of universe ending events? [closed]

or is it that the definition of infinity used here excludes such events like there are an infinite number of odd numbers but 2 isn't in that set?
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1 vote
1 answer
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Shouldn't the estimate of the universe's age be higher, not lower, after the attractive strength of gravity is taken into account?

From 'Fundamentals: Ten Keys to Reality', by Frank Wilczek : "Running the movie of cosmic history backward in our minds, we found the galaxies all coming together to meet at a definite time. ...
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4 votes
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Significantly blueshifted Lyman-$\alpha$

Lyman-$\alpha$ line in galaxies is notably known to show a double peaked profile, mainly due to its scattering in a moving medium, see e.g., the very recent Matthee et al. 2021, The X-SHOOTER Lyman-α ...
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2 votes
2 answers
102 views

Potential paradox with the Big Rip and the Multiverse?

I came up with this confusing theory a few years ago, but did not ask it on this site. If the Big Rip and the Multiverse theories are true, then when the Big Rip occurs, the universe's size will ...
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How long does it take for a galaxy (or other object) to disappear behind the cosmic sight horizon?

After looking at this question, I am wondering, how long does it take for a galaxy or other space object, to disappear from our view from the Milky Way due to the expansion of the universe? Assume GN-...
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0 votes
0 answers
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How does the universe create more universe ( expand ) out of nothing? [duplicate]

By the law of conversation of energy, mass and matter, how does the universe get the energy to expand itself, and also expand faster than light!! Edit : my main question is that if the matter, energy ...
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8 votes
1 answer
1k views

What are the stages in the life of a universe?

Geological periods describe varying phases in the last few hundred million years on earth. Are there any names for the periods on a timescale 1-2 orders of magnitude greater, that is, for the stages ...
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6 votes
1 answer
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Universe’s Glow Shows There Are Fewer/More Galaxies Than We Thought, Say Scientists

There are several articles like this: Universe’s Glow Shows There Are Fewer Galaxies Than We Thought, Say Scientists NASA’s New Horizons spacecraft beyond Pluto has made a groundbreaking measurement ...
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15 votes
3 answers
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Can there be planets, stars and galaxies made of dark matter or antimatter?

We know that the universe has more dark and anti matter as compared to normal matter. Can there be dark matter galaxies or antimatter galaxies?
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1 answer
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Centre of the Universe [duplicate]

Why shouldn't the original singularity of the big bang happen to be the centre of the Universe? Assume that the universe is expanding isotropically with a constant speed.
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Where can I find galaxy spectra (in the form of FITS files)?

I know there's SDSS and I tried searching for the spectra through the navigate and explore tool under CAS as well as by using RA/Dec coordinates under SAS, but every single time it comes out with 0 ...
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1 vote
2 answers
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List of galaxies with their dark matter halo

Where can one find the list of galaxies with their dark halo masses, I've searched several sites but I found no such proper list where the masses of their dark matter halo is compiled? Can anybody ...
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1 vote
0 answers
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Do apparent magnitude (V) and photometric magnitude (specifically in optical V band between 500-600 nm) have a similar scale to stellar magnitude?

I'm graphing a table and I used the magnitude values from this database https://vizier.u-strasbg.fr/viz-bin/VizieR-4 (It's the V/19/data catalog for "Masses and Ages of stars in 68 open clusters&...
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1 vote
1 answer
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What is a UBV source for stars or stellar objects?

I was using the V19(VizieR) catalog and the main identifier of the stars was in terms of an 'ID' number which they mentioned as being 'Star number in UBV source' I have no idea what that means. How ...
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-2 votes
1 answer
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Was our Universe born inside a Black Hole [duplicate]

Is there any possibility that our Universe was just born inside a Black Hole? If so, then mathematically prove that it happened and if it didn't happen, then please mathematically disprove it.
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40 votes
3 answers
11k views

How do scientists know that the distant parts of the universe obey the physical laws exactly as we observe around us?

How do scientists know that distant parts of the universe obey the physical laws exactly as we observe around us? The question might look a bit odd but I am really stuck on my head. We know, ...
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0 votes
0 answers
87 views

Is the Universe infinite? [duplicate]

https://en.wikipedia.org/wiki/Universe Is the Universe infinite or finite ?
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0 answers
64 views

Was universe spawn from nothing? [duplicate]

Was universe spawn from nothing? Until now, scientists figured out that the Big Bang happened from a tiny particle which was infinitely energy densed and having infinite mass. If that is the case ...
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3 votes
1 answer
180 views

Is most hydrogen in the universe in the form of plasma, atomic neutral hydrogen, ionized hydrogen, or molecular?

I have had trouble finding an answer somewhere.... Some places say most hydrogen is plasma, such as the stuff stars are made of (mostly) and the 'warm-hot intergalactic plasma'. Other places say ...
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1 vote
1 answer
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Does the critical density of the Universe also include Dark Energy?

It is often said that it seems that the Universe is quite close to critical density (for example https://astronomy.swin.edu.au/cosmos/C/Critical+Density). Does this include Dark Energy as well (apart ...
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3 votes
1 answer
227 views

What is the shape of Universe?

What we can assume by the shape of universe. As I know when we talk about universe we talk about multi dimension structure but that structure should have some shape. I wonder that if we look the ...
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3 votes
1 answer
388 views

When will all other galaxies become not visible from Earth/Milky way?

I know that because of the universe expansion, at some point we will not see any other galaxies from Earth, and we will be able to see only our own galaxy. Does anyone have an origin or time ...
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2 votes
0 answers
79 views

How did we measure the mass of the universe?

In an wiki article, observable universe, it was mentioned that, Mass (ordinary matter) 1.5×10^53 kg I wonder how did we measure the mass of our observable universe?
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1 vote
1 answer
60 views

Picking two random points in space and drawing a line between them, what is the chance the line intersects anything?

I thought of this question after pondering how most of the observable universe is observable. If we can observe it, then the space between us and that object must have been unoccupied to allow the ...
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0 votes
1 answer
232 views

How can something infinitely big have expanded from an infinitely small?

Please help me reconcile what I see as contradicting theories: The universe began with the Big Bang and expanded from an infinitesimally small point. The universe is infinite. How can something ...
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