Questions tagged [dark-energy]

Questions regarding the as-yet-unknown energy permeating the universe that is responsible for its expansion.

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82 views

In what form was dark energy stored 6 billion years ago?

Bearing in mind the provisions of the 1st Law of Thermodynamics, which decrees that energy can neither be created nor destroyed, all the energy in the Universe must have been there at the time of the ...
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How are constraints on dark energy improved the most?

Today we have various data available from independent probes to constrain dark energy, i.e. its equation of state $w$. These include Type 1a supernovae, BAO, CMB, large-scale galaxy surveys, etc. Are ...
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156 views

Has the Big Crunch been ruled out?

If the dark energy equation of state $\omega$ evolves with time, and becomes larger, this would result in decelerated expansion and eventually a Big Crunch. If $\omega$ decreases with time, becoming ...
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If objects don't move when the universe expands, how can the expansion result in redshift?

I am approaching this topic from a layman's perspective and view this as a logic puzzle, but when someone tries to get me to accept the logic, I'm never convinced by their arguments. According to ...
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89 views

Are gravitational waves part of dark energy?

Do the current models of the universe consider the energy release of gravitational waves? E.g. iirc, the last black hole merger detected had a gravitational wave energy equal to ~3 solar masses (hope ...
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Can the Dark Energy be Pauli pressure?

Some neutrinos are fermions. There are quite of few of them out there. Could their degeneracy pressure give rise to an expansion force to explain Dark Energy?
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96 views

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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Can eternal inflation and gravity explain dark energy?

First of all, I have absolutely no background in astronomy and physics. I just watch a lot of "i-hope-scientific" youtube channels talking about physics and astrophysics and I can kind of follow the ...
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97 views

Are there Dark Stars

In the visible universe, we have a lot of matter to energy conversion going on in stars. Is there an equivalent structure that is converting dark matter to dark energy?
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107 views

What is the closest candidate for Dark Matter currently?

I've both fascinated and frustrated after learning about the existence of Dark Matter. Can we find evidence of Dark Matter within our Solar system? What is currently the closest candidate for Dark ...
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235 views

Influences from outside the observable universe explaining dark energy and expansion?

Could some influence from outside the observable universe be causing the expansion?
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61 views

How might WFIRST help us better understand dark energy?

In the video linked in the Space.com article What Would It Mean for Astronomers If the WFIRST Space Telescope Is Killed?, (available in YouTube as WFIRST: The Best of Both Worlds) after ...
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2answers
255 views

Does gravity repel when dark energy is involved?

So I am currently reading the book We have no idea by Jorge Cham and Daniel Whiteson. In one of their chapters they talk about how gravity is a force that only attracts and doesn't repel, most of the ...
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562 views

Relationship between Dark Energy and Dark Matter

I have encountered two seemingly contradictory theories on this(I don't know which one of them is correct, or where I am wrong):- From Wikipedia: Measurements of cosmic microwave background (CMB) ...
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224 views

What is the distribution of dark energy?

Dark matter is not distributed evenly. It forms clouds, it concentrates in galaxies, it forms hairs around celestial bodies. A google search for dark energy distribution floods me with dark matter ...
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347 views

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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1answer
132 views

How strong is the gravity from half of the distant universe?

I would like to know, how strong would the gravity be from the distant universe if we were somehow able to remove half of it. For example, if everything behind us did not exist, how strongly would ...
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219 views

How strong is the gravitational stretch we experience from the edge of the universe?

How much gravitational effect do we experience (e.g. maybe -.00001 G or smaller) from the edge of the visible universe? By edge of the visible universe, I am talking about the region of the cosmic ...
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150 views

Could Dark Energy be a “Cosmic Gravity Background”

Could dark energy (the accelerating expansion of the universe) be the result of gravity from the dense past universe "pulling" outward from all directions? The universe theoretically started out ...
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215 views

Why is dark energy density given in grams per cm$^3?$

According to Wikipedia article, The density of dark energy ($~ 7 × 10^{−30} g/cm^3$) is very low, much less than the density of ordinary matter or dark matter within galaxies. However, it comes to ...
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Are they talking about the observable universe or the unobservable universe? [closed]

When people say that 95% of the universe is dark matter and dark energy, are they talking about it being in the observable universe or the unobservable universe? Because surely all matter in the ...
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94 views

How do you measure something that has already left the observable universe?

They say that the observable universe is only 5% of the entire equation. The rest of it consists of dark matter and energy. I believe that they are trying to find a way to see something that cannot be ...
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109 views

Can the diminishing energy of the CMBR be the source of dark energy?

I was just told the CMBR energy diminishes with time. Can it be that the lost energy is somehow transferred to spacetime, causing the expansion to accelerate?
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830 views

Can virtual particles be the source of dark matter and dark energy? [closed]

I had this question for a long time. But otherwise the question basically sums the whole thing up.
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106 views

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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575 views

How is the Universe's Expansion Accelerating if the Hubble Constant is Decreasing?

I am just getting into the field of cosmology and was wondering what it means practically to say that the Hubble Constant is decreasing while the expansion rate of the Universe is accelerating. I am ...
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141 views

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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124 views

Could dark matter be “inside-out” reality?

Where we are, and in the conventional galaxies etc. that we see, there is a whole lot of relatively uniform space but in isolated places within that space, there are pockets of concentrated "mass" ...
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Conventional matter to dark matter ratio, outside of galaxies (Bounty!)

I'm pleased to offer a bounty to attract more attention to the fantastic Astronomy site. Consider say this outstanding diagram from another question, To begin with galaxies have a typical density D. ...
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146 views

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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200 views

Is nucleosynthesis responsible for the expansion of the universe?

Is it just a coincidence that the two major expansionary periods occur close to periods of nucleosynthesis? Big Bang nucleosynthesis occurred very close to the inflationary period. Supernova and ...
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315 views

Will gravitational waves too far away ever reach us?

Gravity is the curvature of spacetime, and its effects travel at lightspeed. However, space is expanding; eventually, light from distant galaxies will become more and more redshifted, and we will no ...
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3answers
236 views

Can “dark matter” be the additional mass from the speed of the Galactic Cluster?

Considering that the Earth orbits the Sun at 100 000 km/h and that the Sun orbits the Milky Way at almost 1 000 000 km/h, could it be possible that the galactic cluster orbits some super cluster at ...
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128 views

What's the relation between Einstein's Gravitational Theory and Dark Matter?

I was reading an elementary book on dark matter (in fact, a historical perspective) and there were mentioned how the scientific community react to the idea of dark matter proposed as a solution to ...
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702 views

If the Universe is infinite, would heat death be impossible?

If the Universe is infinite, one would imagine that if we kept moving through space, we'd constantly find newer and newer galaxies and objects forever. This would imply that there is an infinite ...
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358 views

could dark energy be a force coming from the hyperspace outside the universe?

It seems to me that the expansion of the universe is only being looked at one way. a repelling force, basically being the opposite of gravity. After pondering this for many nights, I began to wonder ...
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171 views

TIME TRAVEL-Can it be really done? [closed]

Is it posssible for us to time travel? Is light essential factor or the dark matter and dark energy?
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176 views

Relationship between the Casimir force and dark energy

This is related to another question I asked. Might we actually be observing dark energy when we do experiments that verify the Casimir effect?
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1answer
106 views

The largest discrepancy in the history of science

I watched a cosmology lecture given by Leonard Susskind that convinced me to put my money on dark energy being a pressure caused by energy that is evenly distributed throughout the "vacuum" of space. ...
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2k views

Does the universe expand at the same rate everywhere in the universe?

Specifically, I am wondering if some areas of the universe expand faster than other areas and whether the faster expanding areas diffuse the expansion through the slower expanding areas or does the ...
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194 views

Why is dark energy preferred to the cosmological constant?

Dark energy and the cosmological constant are often identified, but Peebles and Ratra explain that "Einstein did not consider the cosmological constant to be part of the stress-energy term... a ...
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2answers
164 views

Would dark energy save the earth for a while as the sun heats up?

Would the expansion of space (e.g. dark energy) move the earth further away from the sun over time, possibly saving us for perhaps a few billion years as the sun heats up? Scientists now tend to ...
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118 views

Is dark energy evenly spaced throughout Universe?

Are there certain parts of the Universe that are expanding faster than others? Is there anyway to definitively measure this?
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165 views

Is there a connection between black holes and dark matter/energy?

Is there a spatial or gravitational relationship between black holes and dark matter/energy?
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128 views

What are dark matter and dark energy? [closed]

I've recently read about dark matter and dark energy. But unfortunately, there were not enough answers for me. The article I read was more of a hypothesis than a real answer. So I'm asking for all the ...
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1answer
138 views

Is the dark energy between the moon and Earth measurable in any capacity?

What are the experiments, or measurements, that can detect, or account for, dark energy involved in making calculations concerning Earth and its only natural satellite?
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99 views

why do we look at dark energy as an energy?

We call dark matter dark matter, because of the way it acts on galaxies, but why do we look at dark energy as an energy? With $E = m c^2$, can't dark energy be mass as well? Why dont we look at dark ...
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How can light reach us from 14 billion light years away?

One thing that I can't quite wrap my head around is how light is traveling to Earth from 14 billion light years away, aka the beginning of the universe. The way I see it, the universe itself was very ...
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151 views

Is dark energy constant?

Does the "amount" of dark energy in the universe change over time, or is it constant? The dark energy I am asking about is the rate of acceleration of the universe's expansion.
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190 views

Dark Energy Expansion

The new Cosmos extra features mentions that at about 6,771,500,000 years ago the universe began an accelerated expansion. How do we know this? What evidence do we have for this renewed and accelerated ...