Questions tagged [universe]

Questions regarding all of time and space and its contents.

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1answer
42 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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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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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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1answer
112 views

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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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?

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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4answers
2k views

Does the universe have an edge?

I've heard the universe is just an empty cavity. Does the universe have any edge or stop or is it just an infinite empty cavity?
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5answers
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Does the Milky Way move through space?

Does our galaxy moves through space? Or does it stay in a single location? If it does move, what causes it to move?
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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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193 views

As the Universe expands, do things like planets expand also, or just the space in between?

Just what the question says. As the universe expands, and space expands, do objects like planets ever expand? Does the space INSIDE of those objects expand?
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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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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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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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50 views

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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The energy density of DM (to be fluid,state parameter=-2)increases with time. Does it violate the concept of accelerating universe?

We know that dark energy with value of state parameter $\omega<-1$ is called phantom dark energy model. In this model if we assume dark energy to be a fluid with value of state parameter $\omega=-2$...
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Fate of the Universe

Which scenario will be worse for the ultimate fate of the Universe, forever expanding or the "Big Crunch"? Will the Universe be destroyed in both scenarios? At the present time does it appear that it ...
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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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3answers
153 views

Is the eventual heat death of the universe due to the expansion of the universe?

I am reading about the accelerating expansion of the universe and something struck me. The observation that things further away were accelerating away faster and that early observations made it look ...
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1answer
736 views

What will the universe be like in a googolplex years time?

It will be cold and dark in 10^(10^100) years. What else can be said of the state of things in the far distant future? Will everything have fallen into supermassive black holes and then radiated ...
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Why black holes are extremely cold?

"The most massive black holes in the Universe, the supermassive black holes with millions of times the math [sic] of the Sun will have a temperature of 1.4 x $10^{-14}$ Kelvin. That's low. Almost ...
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Does time slow down because the universe is expanding at an accelerating rate?

If the universe is expanding at an accelerating rate, such that the galaxies' moving away from each other is accelerated, then time should also slow down. And when universe will accelerate to the ...
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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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how are the celestial objects measured? [closed]

So I am guessing that chemical composition of the starts is measured using the spectrum analysis of waves emitted by them. But what if the spectrum is super packed by different wave lengths? How do ...
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Why is there a difference between the cosmic event horizon and the age of the universe?

According to wiki the cosmic event horizon is 5 Gpc but the age of the universe is about 13,7 billion years. Usually light from far galaxys needed at most 13,7 billion years to reach the earth so the ...
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Is there a star over my head?

Say I'm standing up straight, and I draw a straight line from my core through the top of my head (perpendicular to the ground). What is the probability that that line intersects with a star? EDIT: I'...
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Do we know what happens at the boundary of the universe, what are some theories about it? [duplicate]

Do we know what happens at the boundary of the universe, what are some theories about it? Does space time differ at the boundary? Do things become larger at the boundary? Do the trajectories curve and ...
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3answers
195 views

Does the universe curve in on itself?

I've read a little bit about the universe, but its not clear to me if there is a place in the universe beyond which there are no stars. For example, is there anywhere in the universe that one could ...
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Probability of collision of another bubble universe with our universe

This is rephrased from a previous question and expanding on it. Considering the model of an "inflating" universe which extends infinitely in past (and possibly future) time, constantly creating new ...
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How can 'HD 140283' be older than the universe?

Scientists have known about the star HD 140283, informally nicknamed the Methuselah star, for more than 100 years, since it cruises across the sky at a relatively rapid clip. The star moves at about ...
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Energy to expand

I do have a small question, which may seem a bit stupid but we are all here to learn. Anyways my question is: Is the universe expanding using the energy it had from the Big Bang? if so what would ...
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How can the universe be infinite?

I've heard from renowned astrophysicists that we don't yet know whether or not the Universe is infinite. How is that possible regarding the big bang theory is accepted (as they all do)? Are they ...
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225 views

How can cosmological bubble universes “collide” with each other?

In Eternal Inflation Theory, there exists the idea of multiple "bubble" Universes that grow and according to this theory, can "collide" with each other. The paper suggests that you can search for ...
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1answer
644 views

In the end what is the ultimate matter/element in the universe, due to fusion process in stars?

We know that, in stars, hydrogen is used by the stars and due to the fusion in two hydrogen elements we get helium -> Carbon -> Oxygen ->Other elements -> Iron -> then Super/Hypernova. If everywhere ...
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Is the age of the universe relative to an observer's location in that universe?

According to Wiki the age of the universe is 13 billion years old, and I was taught that background radiation made the universe uniform in all directions. Doesn't this define a sphere of space in the ...
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1answer
151 views

Could the Universe really be 12.5-13 billion years old?

My initial reaction is that "this must be wrong" and apparently that's a lot of people's initial reaction according to the article. https://www.nbcnews.com/mach/science/universe-may-be-billion-years-...
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What is the effect of this expanding universe on the energy density of it?

We know that our universe is expanding i.e. volume of the universe is getting larger with time with total energy being conserved. My question is whether the energy density is getting smaller with ...
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The destruction of the Universe by a bubble

So I was watching a documentary on television about this and a number of theories that are proposed as to what the fate of the Universe will be: "Big Crunch" "Big Freeze" "Big Rip" I understand ...
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137 views

Observable universe equals its Schwarzschild radius (event horizon)?

The estimated age of the universe is 14 billion years. The estimated Schwarzschild radius (event horizon) of the observable universe is 14 billion light-years. What are the ramifications?
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What's the largest non-spherical astronomical object in the universe?

Some asteroids and comets are non-spherical. But is the nature of big things and gravity so that large things in the universe are always spherical? What is the biggest astronomical object in terms of ...
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What is the most dense object in the universe?

Inspired by this answer to the question, Why is the Sun's density less than the inner planets?, what is the most dense object in the universe?
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Does the expansion of the universe increase with distance?

I read something in a book the other day which has gotten me really confused. They were talking about the expansion of the universe, and if I understood it all, they said that the expansion of the ...
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Invisible Mass Affecting the Expansion of the Universe

Are there enough neutrinos & other invisible particles in a cubic light year of space to significantly affect the expansion of the universe,& at a very rough estimate without taking into ...
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How is “surface brightness dimming” derived from redshift in the NED extragalactic database

I have several questions regarding “Surface Brightness Dimming” in the “Quantities Derived from Redshift” section of the Nasa/ipac Extragalactic Database. As an example, please use quasar IRAS F08279+...
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how to define the universe itself is expanding greater than than the speed of light?

since we observe galaxies and other steller objects in very tiny tiny scale, and how we can understand that the speed of expansion on universe is higher than the speed of light ? even using the ...
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How many earths fit in the observable universe?

I was pondering our insignificance, when I wondered - how much smaller is our planet then the (observable) universe? And being as I don't know how to do the math, I'm asking it here. So how many of ...
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What covers the outside of the Universe? [closed]

Is the Universe a sphere with water or ice surrounding its' confinement? Are there any theories that imply the Universe being confined within a sphere of water/ice material?
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Are there ways to estimate size of the “whole universe”?

Words escape me, but by "whole universe" (I think) I mean everything that's spatially connected to the observable universe in a conventional sense. If there is a better term for it, please let me know!...

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