Questions tagged [universe]

Questions regarding all of time and space and its contents.

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53 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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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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Can you debunk this argument argument against expanding of universe? [duplicate]

We know that universe is expanding because of doppler effects. Because redshift effects. But redshift effects can be cause be Compton effects, Tired light and gravitational effect. So why do we say ...
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1answer
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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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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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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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1answer
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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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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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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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1answer
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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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1answer
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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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How do scientists know that 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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55 views

Is the Universe infinite? [duplicate]

https://en.wikipedia.org/wiki/Universe Is the Universe infinite or finite ?
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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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1answer
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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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1answer
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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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1answer
169 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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1answer
91 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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76 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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1answer
49 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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1answer
91 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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1answer
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What was the the value of the Hubble constant at the time of the CMB's 'release' (i.e., 379,000 years after Big Bang)?

What about its value roughly 9 billion years after the Big Bang, when dark energy started to 'take over' and accelerate the expansion of the universe? Is there a timeline or chart somewhere that shows ...
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38 views

How to calculate the mass of a galaxy?

How to calculate the mass of a galaxy? I have its apparent angular diameter and its distance. A H2 cloud at the galaxy's disc has a velocity of 410 km/s. How to calculate the mass of the galaxy?
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Bounded Observable Universe; is there an object we once could see but can no longer? [duplicate]

If the universe is expanding faster than the speed of light, then there will be objects (matter or energy or whatever) that previously could be seen, but no longer can be seen, precisely because the ...
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1answer
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Bounded Observable Universe and General Relativity

The book General Relativity for Mathematicians by Sachs and Wu defines a "spacetime" as a connected 4-dimensional, oriented and time oriented Lorentzian manifold. I emphasize the word "connected." ...
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1answer
112 views

What is the composition of the Universe in terms of Types Of Stars?

There are Main Sequence Stars Red Giants White Dwarfs Red Dwarfs Neutron Stars and other types of Stars. How many % of stars are Main Sequence? How many are Red Giants? and so on. I searched ...
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109 views

Will the “fabric of space time” rip from expansion?

I'm quite familiar with the fabric of space time theory and as I've been quite lonely these past few weeks, I started thinking that since the universe is expanding and since the "fabric" is the ...
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2answers
106 views

Is it be correct to say that we live in a young (only 14 billion years old) universe?

From what I have read, it seems that our universe is expected to function more or less as it does now for some $10^{12}$ years, possibly more. If that is correct, our universe's current age of $14$ ...
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what is the acceleration parameter in a universe?

Obtain the value of the acceleration parameter in a universe, including cosmological radiation and constant. what is the exactly acceleration parameter in a universe means ?
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How do we measure the age of the universe?

As mentioned in wiki/Age_of_the_universe, The current measurement of the age of the universe is around 13.8 billion years (as of 2015) – 13.799±0.021 billion years When my friend who is not from ...
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322 views

Will the Heat Death scenario ever occur or just the Big Freeze?

According to the Wikipedia page regarding the ultimate fate of the universe, heat death is a different scenario than the big freeze. It states that in the big freeze, temperature will asymptotically ...
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Why is rotational motion absolute, is the universe spinning? [duplicate]

When considering any object, one can say its translational movement is relative, depending on the point of view or reference frame adopted. If it moves at 1/4c relative to some observer, one might say ...
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1answer
86 views

If a black hole pulls every object in the universe, why there is a light around it?

I've seen some black hole images and I've seen some movies about it e.g(interstellar). I wonder why it has a light around it. Even if I know that light can't escape through it. Can someone enlighten ...
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The Matter Anti Matter Asymmetry

The matter anti matter asymmetry is still a mystery that still can't be explained. But what if there wasn't an asymmetry? Isn't it possible that there was exactly equal amounts of matter and anti ...
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Is the Big Bounce Theory valid? If so does that mean all this have happened before?

IF the universe is just an infinite loop of events from expanding to contracting does that mean all this has happened before? The initial conditions for the next big bang would (or rather could) be ...
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What book(s) should I read to get started learning about astronomy? [duplicate]

I'm an undergrad software engineer but I also love physics and math. I'm starting to get going in AI/Machine Learning techniques and I'm going to use NASA data-sets to conduct analysis. However, I am ...
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Why does the star formation rate correlate with the total stellar mass in star forming galaxies?

The so-called "Main Sequence" of star-forming galaxies (e.g., Brinchmann et al. 2004; Noeske et al. 2007) clearly points to a linear relation between the stellar mass of galaxies and their star ...
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How do astrophysicists handle the topic 'boundaries'?

The naive perception, at least mine, is that in astrophysics the objects of investigation evolve in an infinitely large environment. Since the scenery is so much larger than the events unfolding in it,...
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1answer
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How is the Dating of Samples of Cosmic Objects Performed, Including Pre-Solar Dust?

In the new Space.com article 7 billion-year-old stardust is oldest material found on Earth I had read about some pre-solar grains dating back to 7 billion years. What techniques are used in ...
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1answer
132 views

Does a flat universe mean not finite and circular?

I am trying to wrap my head around what a flat universe means; Trying to imagine why angles of triangles in spherical volumes are different. Because my brain can't do that well and I became a bit ...
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1answer
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Any theories about universal expansion due to action at the universal event horizon?

I'm curious if there are any theories about the increasing rate of the expansion of the universe that are centered around gravitational pull from matter outside the event horizon of either the ...
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1answer
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Anecdote of an astronomer looking for correlations in antipodal pairings of stars; what am I remembering?

The question Are the stars distributed in uniform distribution, on the celestial dome, with respect to brightness? brings to mind a different study that I vaguely remember hearing about a while ago, ...
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Why the space is so dark even there are billions of stars and many quasars emitting light [duplicate]

In our galaxy itself, there are millions of stars, and there are many more other galaxies in our local group and billions in the observable universes. For sure they all emit a lot of light, still why ...
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24th Nov 2019.0515 hrs.GMT +1.saw a line of stars moving in a staright line.straight.what could it be? [duplicate]

While doing our morning navigation watch.. we saw stars moving in line.. it continued for atleast 10 mins.. not a airplane or shooting stars.. Can it be satellites orbiting??
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What makes the planets to be symmetric [closed]

I have seen, in my text books, and on nasa sites, the all the planets are symmetrical. And universe also love symmetry. What cause this symmetry, why the symmetry is important. As we know that ...
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1answer
247 views

Based off of the study that found the universe has a positive curvature, how big would the whole universe be?

This study found that the universe has a positive curvature https://www.nature.com/articles/s41550-019-0906-9. I didn't really want to buy it and see if it says how big the universe might be. I know ...
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1answer
166 views

How do we know so many details about Big Bang, but we do not know if Universe is finite/infinite?

I understand that this question may be too vague, but I am confused about the following: On one hand we know a lot of "details" about Big Bang, like really precise details, evolution of universe, age ...
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What is the largest cluster of merging galaxies?

Reading about the Andromeda–Milky Way collision, a galactic collision predicted to occur in about 4.5 billion years between the two galaxies, I went to the galaxy merger page and Wikipedia states that ...

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