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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64 views

Kardashev scale [closed]

Why is becoming a type 3 from a type 2 civilization the hardest? I have watched many videos on the topic and still can't figure out why? Also is there a difference in technology between a type 4 and a ...
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Demonstration of scales for the two components (transverse and perpendicular) of Baryonic Acoustic Oscillations (BAO)

I transfer here a post that has not had any answer pn physics exchange, so I am going to delete this latter. Maybe I will have more luckiness here. In an astrophysics context about BAO (Baryonic ...
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37 views

Intuitive explanation for why the Doppler effect (and red-shift) happens?

I was looking for an intuitive explanation as to why the Doppler effect happens. I haven't found any, but this is what I thought: -Waves emitted travel at a constant speed -The source emits a wave -If ...
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38 views

The definition of eclipsing binary star systems

In the second minimum (the 3rd step) there is a smaller decrease in light intensity. For this to happen, wouldn't you need to be looking at the plane of orbit from above rather than directly along the ...
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can we calculate the velocity of galaxies at the edge of the observable universe?

I read this post Does the edge of the Universe travel faster than the speed of light? but there was no calculation, so I tried it thusly: The observable universe is 28.5 Gpc (gigaparsecs) = 28500 ...
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109 views

How frequently do Jupiter & Regulus have triple conjunctions?

I am wanting to know if the triple conjunction of Jupiter with Regulus in: Sep 10, 3 BC Feb 7, 3 BC & May 8, 2 BC with Jupiter later having a conjunction with Venus in Jun 17, 2 BC has happened ...
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I sighted a group of satélites moving in a interesting pattern in a way I never seen from this area where I live is this posible? [duplicate]

I live in the rural area of the state of São Paulo in brasil (mata atlántica). the sky is absolutely clear, when there is no clouds you see the milky way perfectly and a sky full of stars. I just ...
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How is the gravitational effect of galaxies outside of the visible universe on galaxies within the visible universe currently modeled?

Given currently accepted models of the universe, How much mass is outside of the visible universe? What is the gravitational effect of that mass on the visible universe? The question How strong is ...
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With the expansion of the universe is time also increasing?

With more space being created would there be more time in that new region formed? Is the over all universe increasing in time? This is my first question so go easy on me. PS. Would that also mean that ...
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Various stars moving in a line [duplicate]

I from India saw various stars moving in a line from North-West direction to the South-East direction at 5:27 AM on date 13 february 2020... They all are moving rapidly and can be easily seen from the ...
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Earth as a grain of sand

If Earth was a grain of sand in Buenos Aires in what point in this observable universe map would be LA be?
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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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137 views

At what rate is the observable universe expanding?

The observable universe is $4.4 \times 10^{26} m $ in every direction. I told this to my daughter and then added, "And guess what? It's a little bigger today than it was yesterday." "Wow!" But by ...
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Could different views of the universe simply be different points in time?

I'm not sure if this is the correct stackexchange site for this question. I've been reading this article on Vice Motherboard There’s Growing Evidence That the Universe Is Connected by Giant ...
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214 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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What is the hottest thing in the universe?

Straight from my 7 year old to you, exactly what it says on the cover: What is the hottest thing in the universe? To make it Stack Exchange-friendly, I'll add the following caveats: it should be ...
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236 views

How do we know the radius of the universe is 47 billion light years?

Hubble deep field image at maximum resolution shows a few of the furthest galaxies very small & faint, only just visible, but suggests that there is more to see beyond if only the resolution were ...
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130 views

What Is The Maximum Distance Our Finest Instruments Could See When They're Perfected?

Radius of the observable universe is 47.5 billion light years,which means we are seeing things which are about 48 billion light years away. At a rough estimate,at what distance would our finest ...
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139 views

How much of the Universe is invisible to us, and how does it affect our theories?

I watched an interview with Neil deGrasse Tyson on The Late Show with Stephen Colbert where he briefly mentioned a disturbing thought. It is something that I have never thought of before, and the idea ...
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How has the estimate of the number of stars in the universe changed over time?

Current estimates for the number of stars in the universe are about 10^22. However, that number has changed several times as new observations have come forth. How has the estimate of the number of ...
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What exactly is wrong with this plaque in Neil deGrasse Tyson's “back yard”? Has it been fixed?

The Wikipedia subsection Observable Universe; Misconceptions on its size shows this image of a plaque, with the caption: An example of the misconception that the radius of the observable universe ...
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Ideas about the origin of the “black hole - galaxy mass” relation?

It has been extensively shown that the mass of black-holes located at the center of galaxies scales with several galaxy properties, most notably the stellar velocity dispersion of the stellar bulge, ...
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Can the range of the observable universe be extended through an intermediary?

I understand that the so called observable universe has a limit we cannot see through. My question is whether we might get information through an intermediate hypothetical actor located halfway to ...
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Expansion of space - how do we end up with an unobservable region?

I've just been answering a question on this issue,in physics SE,and realised that my answer conceals a point I don't myself understand. I understand that The expansion of metric isn't affected by ...
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30 views

How far out would we need to travel to measure the “constant observer”?

One hypothetical tenet of much astrophysics is that the Universe is uniform on large scales. This actually hinges on many deep theoretical results from astrophysics, since what we actually observe is ...
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Terminology for empty space at the edge of the observable universe?

Is there a name for a point at the edge of the observable universe at which there is no visible matter, that appears completely dark? I'm thinking something like "empty space", but that could equally ...
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Where is the North of the Universe

Does it exist North of the Universe? (Which is probably used for determining coordinates of far galaxies.) If so, then where it is? On what is it aligned? (Is it orientated on Earth, Sun, Milky Way, ...
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Necessary steps to calculate photon's path by using null geodesic equation

Can anyone please give me an explanation on how to calculate photon's path by using the null geodesic equation? N.B. I know all of the non-zero values of Christoffel symbols.
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Can two planets in an empty universe meet/be pulled together?

For this question assume that the entire universe is completely empty. The universe is not expanding or contracting, it is completely motionless since time immemorial and has never moved before. Only ...
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116 views

If the whole observable Universe is as big as planet Earth, how big would Earth be?

If the whole observable Universe is as big as planet Earth, how big would Earth be?
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What was the process of calculating how much darkmatter/matter/dark energy the observable universe consists of and how did it come at this conclusion

In 2015 the Planck satellite consortium released an analysis of data collected by the Planck satellite that showed this percentage break down of the universe’s mass/energy. Ordinary matter: 4.9% ...
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711 views

Is our universe stable or metastable?

I've been reading and thinking about this subject for some time, but I can't seem to find a clear answer. After reading Q14: Aspects of the Higgs boson suggest that our Universe is only “...
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Can Einstein-Rosen bridges - if they exist - link two points of which one lies outside of the observable universe of the other?

So there's stuff very far away that is, due to expansion, accelerating away faster than the speed of light, so fast that its light will never reach us even with infinite time - and we can't reach that ...
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how do we know the universe is STILL expanding?

According to Hubble more distant galaxies are moving away faster but since the light took billions of years to reach us we should say they WERE moving away faster billions of years ago. How do we know ...
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Is the acceleration of the expansion of the universe a direct observation or an interpretation?

Is the acceleration of expansion we observe with supernovae direct or is this an interpretation according $\Lambda$CDM model ? I mean what we observe is luminosity distance versus redshift, so to see ...
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526 views

Why there are less massive stars than low mass stars?

What factor determines the selection of star mass? And how we know that the number of massive stars is less than the number of low mass stars?
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157 views

How thick is the cosmic microwave background, including the part we cannot see within the observable universe?

What I want to know is how thick the observable universe is from the point of the cosmic microwave background and beyond. It appears the thickness of the cosmic microwave background itself (the part ...
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Light beam (1 photon) in the limited universe?

If our universe is not infinite, what happens with the light beam (or photon) when it will travel through the whole universe? For example, observable universe according to wikipedia has diameter 93 ...
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Yet another Question about the expansion of universe

A galaxy 13 billion light-years distant is 94% of the way to the big bang. The universe was 800 million years old when the light was emitted. That galaxy today is traveling away from us at 94% of the ...
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Does the CMB pattern evolve in a human lifetime?

I was thinking, as CMB is a snapshot of a slice of the Universe during recombination, how much the cmb is changing with time ? I mean as we progress in time we look a CMB a bit more faraway each time, ...
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336 views

What is the present day radius of the observable universe?

The radius of the observable universe is generally taken to be ~45 billion light years. However, we see distant galaxies as they were many millions of years in the past, so there are two ways I can ...
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243 views

Is the shape of observable universe and shape of space same?

I have read that Euclidean space is considered as flat space and Minkowski space is flat space-time. So when we say our observable universe is flat are we saying that the space is flat or space-time ...
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Bousso bound within particle horizon, discrete Q.field theory

I have 2 questions: Could you please give me arxiv numbers of papers dealing with the Bousso bound for the particle horizon (known Universe), from masters level upwards, with also some papers a bit ...
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Is there a physical limit to how far we can go?

Is there a physical limit to how far we can go? I am thinking there could be based on the following: 1: There are parts of the universe expanding faster than the speed of light that we will never be ...
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If I look beyond (about same region, higher redshift) a galaxy, will I see its progenitors?

Is there a range of redhsift dz, such that if I look at z+dz from a massive object at redshift z, I will see its progenitors? (in a LCDM scenario of halo assembling, with smaller halos evolving ...
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false to stable vacuum transition [closed]

if the universe transitioned from a meta-stable vacuum to a stable vacuum we assume a universal death scenario. However since it cannot propagate faster than the speed of light, from any particular ...
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Can an infinite universe explain the Fermi Paradox?

Explanation of potential problem: We're not completely sure exactly how unlikely an event Abiogenesis was, given both the extreme unlikelihood of nucleotides randomly assembling into anything making ...
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510 views

What is beyond the observable universe? [closed]

What is beyond the edge of the observable universe? Scientists say that the Big Bang is the cause of all creation in the known universe, but it would seem the bang must have happened in the center of ...
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702 views

How can the universe be expanding faster than speed of light? [duplicate]

So the story goes like this: A long time ago, 13.799±0.021 billion years to be exact, something happened. It was a big bang, loud explosion and universe came to existence. It grew and grew, and now ...
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897 views

Maximum distance light can travel? [duplicate]

If we assume that there is nothing except the sun in the universe then how far the light can travel ??