Questions tagged [dark-energy]

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

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2
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1answer
377 views

Why would a quantity like the 'Hubble contrast' be squared, then have its square root taken?

From Sabine Hossenfelder's recent video, New Evidence AGAINST Standard Cosmology: And her source.... I don't get why a graph would show a quantity that is squared, then immediately 'square-rooted'......
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0answers
40 views

How much does the Higgs field contribute to the energy of empty space?

The Higgs field was not spontaneously broken when the universe was young and hot (like I am not...:)). At the very high temperature that existed back then, the Higgs' energy of the Higgs field was non-...
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2answers
83 views

How the data collected during 5 year DESI operation will be analyzed with regards to finding what dark energy really is?

Dark Energy Spectroscopic Instrument, or DESI at the end of it's 5 years operation will create the largest 3-D spectroscopic map of the universe. How the data collected during 5 year DESI operation ...
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1answer
41 views

Dark Matter Density Parameter Variation

The definition of the dark energy density parameter is $$\Omega_{\Lambda} = \frac{\epsilon_{\Lambda}}{\epsilon_c}$$ where $\epsilon$ is the energy density, $\Lambda$ subscripts represents dark energy ...
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2answers
71 views

Can Quantum tunneling be possible within Blackhole ? And if so, could that be the source of Dark Energy?

Quantum tunneling starts happening when there are empty energy states available for the electrons to occupy and the energy barrier is of the order of the wavefunction of the electrons. Could there be ...
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1answer
98 views

Energy conservation of the universe

I have tried to derive an equation for the total energy of the universe. I have found that, $$E(t)= \delta\dot a(t)^2a(t)\Omega(t)$$ Where $\delta$ is just a positive constant, a(t) is the scale ...
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1answer
58 views

Are virtual particles the dark energy that curves spacetime negatively?

Dark energy is said to be the cause of the accelerated expansion that all galaxies in the universe seem to have wrt each other. This is said to be caused by an accelerated expansion of space itself, ...
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3answers
185 views

How is it possible that a universe with mass does not have curvature?

I may know the answer to my question. Mass must curve the universe but the pressure due to energy density may curve the universe in the opposite direction, leading to a flat universe, if they exactly ...
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1answer
68 views

Demo to get Matter Power Spectrum in cosmology

I would like please to demonstrate the expression of Power spectrum in Cosmology : First, I have the relative contrast: $$\delta_{i}(\vec{x}, z) \equiv \rho_{i}(\vec{x}, z) / \bar{\rho}_{i}(z)-1\quad(...
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2answers
81 views

Could blackholes warping space-time create dark energy?

I think the effects of blackholes on the surrounding space is localised to a small area around the blackhole but I wondered if the largest blackholes at the centre of massive clusters could be a ...
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1answer
226 views

What are GEODEs?

Phys.org's Researchers predict location of novel candidate for mysterious dark energy says that GEODEs may explain the dark energy problem. I'm not an astronomer but I've never heard of GEODEs. I know ...
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1answer
63 views

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
141 views

What is dark energy made of? [duplicate]

What are the fundamental constituents of Dark Energy? Can we quantize dark energy in the first place, if it is a kind of Energy?
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1answer
235 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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1answer
80 views

Was Guth inflation propelled by what we now call "Dark Energy"?

The more powerful our telescopes become, the more we are able to see earlier and earlier remnants of Guth Inflation. Assuming that it makes sense to associate a location, BB, in space-time where the ...
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0answers
62 views

Definition of space - to cope with "space expansion"

I've searched quite a lot but found no satisfying definition, so please: How do we actually define space when talking of "space expansion"? Isn't it just a metric, a dimension we measure, instead of ...
2
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1answer
157 views

Why dimmer high-redshift supernovae means the expansion is accelerating, if the dilated region pertains the distant past?

I must be seeing this wrong, because it seems to me the data indicates faster expansion in the past, contrary to Adam Reiss' study that led to the birth of the notion of 'dark energy'. In Reiss' ...
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0answers
70 views

Formula to Compute sigma8 for correction in non-linear regime

I try to explain my issue on this forum since it seems to be appropriate. I need to apply a correction on $\sigma_{8}$ between linear and non-linear regime to keep it fixed (I make change the values ...
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2answers
752 views

How exactly will DESI simultaneously capture individual spectra from 5,000 galaxies using optical fibers?

The BBC News article Telescope tracks 35 million galaxies in Dark Energy hunt says: The aim of the five-year programme is to shed light on Dark Energy - the mysterious force thought to drive an ...
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2answers
124 views

The origins of Dark Matter/Dark Energy

Layman here with an affinity for astronomy, space and everything associated with it. I'm a big fan of the space oriented programs on the Discovery and Science channels and I was watching an episode ...
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1answer
127 views

Can expansion of space blueshift galaxies with respect to one another?

Suppose we have two galaxies in an otherwise devoid space, and suppose the galaxies are gravitating. Suddenly, dark energy kicks in, and accelerated expansion of space begins ... (1D force diagram. ...
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1answer
151 views

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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2answers
196 views

Can dark energy or dark matter affect black holes

I was wondering if black holes are the greatest force of gravity how does other highly spoken about concepts such as dark energy or dark matter compare. Can a black hole absorb dark energy or dark ...
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1answer
166 views

Dark energy and light red shifting

When light is red shifted from distant galaxies, the photons have lost energy. When dark energy pushes objects apart, those objects have gained energy from a larger gravitational potential. Is the ...
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1answer
119 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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0answers
56 views

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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1answer
267 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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2answers
230 views

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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1answer
147 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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1answer
103 views

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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1answer
112 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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1answer
168 views

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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1answer
117 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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1answer
182 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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4answers
349 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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1answer
64 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
402 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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2answers
819 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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1answer
270 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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3answers
589 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
142 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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1answer
271 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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2answers
184 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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3answers
341 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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2answers
357 views

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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2answers
110 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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1answer
116 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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1answer
2k 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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1answer
118 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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5answers
2k 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 ...