Questions tagged [universe]
Questions regarding all of time and space and its contents.
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Based on the smallest number of photons that can deliver information about a star, what is the largest size of the universe?
I was watching a summary video about the Banach-Tarski paradox and it led me to a question.
If I (a) assume the universe is infinite and (b) assume it is possible to receive a single photon of light ...
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What exactly is the "paradox" in Olber's Paradox?
To the extent of my understanding, Olber’s paradox states that if the universe was static and homogeneous, we should see a star at every point in the night sky and therefore the night sky should be ...
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Why aren't other kinds of energies considered in the mass-energy of the universe?
Mass-Energy of the Universe:
5% ordinary matter,
27% dark matter,
68% dark energy
What about other energies such as thermal energy, potential energy, kinetic energy, chemical energy, and radiant ...
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How can we say that the universe is expanding [closed]
How can we say that universe is expanding as we r sure about that
energy is neither created nor destroyed
then from where does this more energy come from
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What questions will we be able to answer if we find life on other celestial bodies? [closed]
Will that be able to answer questions such as our origins or why we exist? Will it unlock some sort of new perception towards anything?
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Total mass of light? [duplicate]
I know that light is considered as energy, and as such has a mass.
So it is certainly taken into account in universes models and calculations.
So I'm wondering: How much of the total mass of the ...
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How does dark energy remain constant?
According to cosmological constant, dark energy should have a constant density but since the universe is expanding so is the volume of the universe and so should the mass of dark energy.
But how does ...
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Is our universe flat?
I heard our universe is flat. Then one question is puzzling in my mind. If our universe is really flat, why we measure distance from any point across in a spherical way. In other words, why we say, ...
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The # of Estimated Galaxies increased 10 fold. Where does that leave our # of stars estimate?
I have found oddly different answers through my multiple google searches.
I found one article that mentioned this did not alter the estimated number of stars in the universe. Link: http://www....
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Finding equation for energy density of matter
I'm trying to get an equation for the energy density of matter of the universe $\rho(t)$, assuming the number of particles is conserved and rest mass energy is much greater than kinetic energy. $\rho(...
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Will we start seeing galaxies disappear due to Universe expansion? [duplicate]
Does the fact that universe is currently expanding at an accelerating rate means that far far away objects (FAO) might start disappearing with time, set aside the "red shift"?
I'm saying this ...
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How can the observable universe shrink in a Big Rip?
As far as I know, the Big Rip occurs when the scale factor reaches infinity in a finite time. This will only happen in a universe dominated by phantom energy (i.e. a universe with an equation of state ...
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What existed before the big bang [closed]
What existed before the big bang?
What all thing are there inside big bang object ?.
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Who first hypothesized that the universe is accelerating?
I couldn't find this answer anywhere. Before 1998, was there a notable physicist who conjectured that the universe is accelerating and perhaps even submitted some equations to support it (and the ...
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What is high redshift?
I'm curious about the difference between low redshift and high redshift universe. Is there any defined limit of redshift beyond which we call things high redshifted?
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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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Latest cosmological parameters
I'm looking for the latest values (with uncertainties) of the four main cosmological density parameters $\Omega_i$ :
\begin{align}\tag{1}
\Omega_{\text{mat}} &={} ?,
&\Omega_{\text{rad}} &=...
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If a star orbited another star, how would that affect parallax measurements of the other star from the vantage point of the first?
Example:
If hypothetically, the vantage point would move 2AU along an orbit around the star being measured, would that make it seem as if the other star moved twice the distance over the back-drop?
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How can space expand in accelerating speed when dark energy is constant?
I came to know that dark energy is constant.As mentioned in the Friedmann equations
How can a constant energy cause an ...
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How is a Galaxy formed?
How is a galaxy formed? I know that the center of our galaxy is considered to be Sagittarius A* and it's surrounded by a lot of stars (also a lot of neutron stars).
But what makes this happen? I mean,...
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Centerless expansion or a matter of perspective [duplicate]
I get this question a lot:
Where is the center of the Universe?
I see this question on the internet all of the time:
Where is the center of the Universe?
Now I have a question regarding all ...
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Does the recent news of "ten times more galaxies" imply that there is correspondingly less dark matter?
Nature: Universe has ten times more galaxies than researchers thought
NASA feature: Hubble Reveals Observable Universe Contains 10 Times More Galaxies Than Previously Thought
Headlines sometimes ...
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Why are galaxies distributed as walls and voids, or spider webs?
I have wondered why the "walls and voids" of the cosmological galaxy distribution seem to resemble a "foam", like rising bread that's ready to fall, with "voids" corresponding to empty bubbles in the ...
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Does the age of the universe take into account General Relativity / Special Relativity?
It is generally accepted that the age of the universe is approximately 12-15 billion years old based on the speed of the expansion of the universe. Since everything is moving very fast away from us, ...
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What suggests the cyclic nature of the universe? Proposed by Stephen Hawking
In "A Briefer History of Time" by Stephen Hawking he writes that if we were to travel faster than the universe were expanding and for long enough (in a straight line) we would eventually come back to ...
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Why are some universal entities round and others are flat?
I've been wondering for a while now why some objects in the universe (such as stars, planets, etc.) are round, while others are flat (galaxies, planetary rings and protoplanetary disks).
I know these ...
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How can we use hypervelocity stars to determine the origins of the Universe?
I was reading this article finding evidence of Universe's origin, which describes that in 1 trillion years we may lose the ability to determine how the universe was created.
The answer seems to be ...
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Is the universe moving through infinite space time as it expands?
What I mean by this, is imagine a person blowing up a balloon. As the balloon expands, the person blowing it up is also walking. At a much grander scale, apply this concept to the universe. As the ...
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Do some ELF (Extremely low frequency) radio waves pass the atmosphere
...reach Earth surface and then are reflected passing the atmosphere again to reach outer space? And once in outer space can they travel indefinetely in it or the interplabetary plasma would stop them?...
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Are there any sounds in space?
Is our universe noisy or silent? Can people hear them? When astronauts are out of the Earth and near an explosion, can they hear its noise.
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If the universe is 'flat', what shape is it? [duplicate]
As in the title, If the universe is considered to be 'flat', what shape is it?
Is it a disc, elliptical, square, rectangle?
Or is this still unknown as we can only study a small segment of the ...
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Can information leave the observable Universe?
From what I gather, the observable universe is expanding at the speed of light. In addition, information cannot travel faster than the speed of light. It seems as though these two facts would imply ...
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Why can we trust Hubble Time if the rate of expansion is not constant?
The age of the Universe can be estimated from taking the inverse of the Hubble constant: $t_\text{universe} = 1/H_0 =d/v.$
It seems to me this method assumes that any given galaxy has been receding ...
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Parts of the Universe Shows Fewer Named Stars [duplicate]
I'm becoming interested in the currently identified stars in the universe. There is a wide swath where much fewer named stars are shown. Why is this?
The image below is a mollweide projection of the ...
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Can one calculate the size (i.e. the radius) of our universe? [closed]
If one can estimate the mass of our universe, might one also calculate its ultimate size, (after it fully expands), based on the Schwarzschild formula for the radius of a black hole? Please note that ...
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If the universe keeps expanding, can we travel to the edge of the universe? [duplicate]
If the universe keeps expanding, is it possible to travel to the edge of the universe?
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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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Is there any proof of space being created?
Is there any proof for space being created?
Because I guess an explanation for the dark energy (dark = our understanding of it) could be that there is a gigantic amount of matter/dark matter that we ...
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In a finite universe, what happens when light reaches the boundary?
If a universe is finite and is not expanding at a speed equal to or greater than c, what happens when light or another form of electromagnetic radiation traveling reaches the boundary?
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Birthday of the Universe
With every improvement of measurement we are able to determine the age of the Universe more exactly. I just wondered how much and what means it would need to narrow the range of age so that it would ...
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Evidence of CMB redshift
Are there any known spectral lines shifted by ~1100? If not, then how certain is mainstream that the CMB has a redshift of ~1100? All I see is a blackbody radiation curve void of spectral lines.
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What is the volume of the universe?
Of course it is not exactly known how big the universe is, but I thougt that the universe is about 100 billion lightyears in diameter. But if that is true can you also make an estimation of the volume ...
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Are we center of universe? [duplicate]
So I just learned that CMB redshift is 1100 regardless where we look (up down left right). According to Hubble's Law that makes it around 46 billion light years away, making it the farthest matter ...
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Locations of farthest matter
Regarding matter that has the highest redshifts, do we see such matter in every general direction we look (relative to Earth: up down left right front back)?
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Is the earth bombarded equally in all directions by neutrinos?
Perhaps it is hard to known for sure because neutrinos are very difficult to detect, although they do go through the earth in very large numbers. But are they passing through the earth equally from ...
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Are there events in universe which we receive first from their neutrino's instead of their photons?
Neutrino's are very small though they have mass. Because of that it is probably that the don't have a speed faster than photons.
But is it in all events, like supernova's or else events, where it is ...
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What are the 10 most abundant elements in the universe by number of atomic nuclei?
I've seen websites that show the ratios of the 10 most common elements but they compare them by relative mass. I think it's more interesting to know the relative abundances of atomic nuclei because ...
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Regarding the age / size of the Universe [duplicate]
I believe the current estimated age of the Universe is around 14 billion years. I just read in another post on here that the diameter of the Universe is around 90 billion light years. This doesn't ...
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What happens outside of the universe? [duplicate]
Since the universe is always expanding, that means there's an edge right? So what are some theories for outside of that growing edge.
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How could we tell if the Universe is infinite? [duplicate]
I've heard from a number of people that the Universe is infinite, and from my perspective, I can't see how this can actually be known, especially given that the Universe started out a finite size and ...
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