Dark energy is the unknown form of energy that drives the acceleration of the universe's expansion.

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Dark Energy & Dark Matter [on hold]

Do we know so little about dark energy and dark matter that it could be all around us and maybe even within our own bodies?
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Is there any primordial gravitational wave(form) that could explain dark energy?

First, I asked myself the question: Is there any gravitational waveform, however fantastical, that could explain dark energy. I suppose for a ubiquitous gravitational wave to be an explanation for ...
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Deceleration parameter in a Universe dominated by the cosmological constant

See Deriving the deceleration parameter of a universe whose density is dominated by matter for a derivation of $q_0 = \frac{\Omega_m}{2}-\Omega_\Lambda$ If the universe were $\Lambda$ dominated, ...
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Source of Dark Energy.

In accelerated expansion dark energy play a crucial role because of negative pressure, but during expansion Dark Energy(DE) do not dilute. DE density is independent of scale factor unlike matter and ...
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Before Dark Energy was discovered

I'm really confused on this topic. Pardon my French if my questions seem really stupid. Before Dark Energy was discovered in 1998 did scientists know that the cosmological constant calculated, I ...
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Deriving the field equations for a dark energy / modified gravity effective field theory

Question I'm trying to derive the modified gravity EFT field equations and, from their 00 component, this Friedmann equation: \begin{equation} H^{2}+H\frac{\dot{\Omega}}{\Omega}=\frac{\kappa \rho_{m}+...
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Dark energy and gravitation force

This might be a silly question to ask but still I had to ask. we know that gravitational force between two galaxies are quite less as compared to the dark energy. so two galaxy are separated at speed ...
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How did the universe shift from “dark matter dominated” to “dark energy dominated”?

In order to get dark energy to dominate, wouldn't you first need another form of energy to push the expansion until dark energy could dominate? Otherwise I don't understand how the universe could ...
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Considering dark energy and other factors, what is the most distant object light could reach?

If we send a photon from Earth at this moment, what is the most distant object that it could reach? This question is partly inspired by this video which states we cannot ever travel beyond our local ...
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Could Dark energy and Dark matter just simply be a warping of spacetime? [closed]

Why do most theories about what Dark energy and Dark matter is make it so that these substances (or not) need to be some kind of undiscovered particle? Would it be possible for Dark energy to simply ...
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How does the inclusion of vacuum energy modify Newtonian gravity equation of motion?

The equation of motion (in the center of mass frame) due only to gravitational forces between two point masses is: $$\frac{d^2r}{dt^2} = -\frac{GM}{r^2}$$ How does the equation get modified when a ...
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Is it possible for dark energy density be decreasing? [closed]

I have an equation relating dark energy density and temperature, actually they have a linear relationship, my question is how to choose the temperature? If I choose the temperature of universe, the ...
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1answer
281 views

What is the difference between the Big Bang Model and the Λ-CDM Model?

If I'm going to write about "The Consensus Model of Cosmology" should I include Big Bang Model or should I go with just the $\Lambda$-CDM Model?
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49 views

Could dark energy and Hawking radiation be the same thing? [closed]

Specifically, could black holes effectively emit some kind of negative mass or other form of dark energy, so that the mass of the black hole itself would actually increase rather than decrease (...
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1answer
59 views

Exponentially accelerating universe, dark energy, the universe's temperature and event horizons.. (sorry in advance!)

Ok.. assume that space-time is accelerating away from itself with a>0 and.. jerk - j⃗ (t)>0 (sorry - don't know how to write "a dot"! :s ).. If this continues on without the rate of acceleration ever ...
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2answers
218 views

How do we know that the galaxies the farthest away from us are actually speeding up?

What i mean is Hubble proved that the galaxies the farthest away from us were moving away faster than the galaxies closer to us. I have a basic understanding of red shift. I've always wondered (and ...
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What is dark matter? Also what is dark energy? I am not duplicating it put just want to write as an article for helping others [duplicate]

Today one of the greatest questions coming up is what is dark matter. also what is dark energy. we don't know much about it still!!! I have tried to bring some light on this question. To prevent ...
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1answer
62 views

Rate of change of temperature of the Universe

Temperature of the whole universe is about 2.7K base on the wmap satellite. I know that temperature has to decrease to time and I have difficult time finding references for rate of change of ...
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Dark energy and virtual particles

If space time is accelerating away from itself everywhere due to dark energy, could this acceleration be the cause of virtual particles, essentially Unruh radiation?
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Can we in the far future have an energy source made from vacuum energy, antimatter, dark energy, Higgs boson? [closed]

Can we in the far future have an energy source made from vacuum energy, antimatter, dark energy, Higgs boson and all kind of these like stuffs?
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Where did all the photon energy go?

From the wikipedia page on dark energy, in reference to the total mass-energy of the universe: The mass–energy of dark matter and ordinary (baryonic) matter contribute 26.8% and 4.9%, ...
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2answers
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Why doesn't the cosmological constant cause black holes to form?

The cosmological constant acts as matter with positive energy but negative pressure. Then a region $R$ should have energy $E\sim \Lambda r^3$. On the other hand, we know that the energy for a black ...
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130 views

What is the amount of dark energy in the Universe, in joules?

I'm toying with an idea, and need absolute amounts of dark energy. I'd also like the same for dark matter. If these values are not estimated, why not?
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1answer
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Could the universe really be expanding at a constant rate? [closed]

I was just thinking, sorry if this idea is idiotic, but since we know galaxies move away from each other at an accelerating rate, could this be due to a weakening gravitational force between galaxies? ...
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1answer
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Was the matter-energy content of our universe always distributed in the same ratios?

Currently, Dark energy (68.3%) and Dark matter (26.8%) together constitute about 95.1% total matter-energy content of the universe while only 4.9% is ordinary baryonic matter. Was this always the case?...
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Could a perfect vacuum exist at the boundary of the universe?

Space is not truly a vacuum because of our observation of quantum foam, but if causality does not exist outside our universe, could that mean that quantum foam cannot exist outside our observable ...
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How come the cosmological constant supports the idea of dark energy existing? [duplicate]

According to an article I've read recently, the cosmological constant was used to support the theory of dark energy. But the cosmological constant already defines an inclination in the essence of ...
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How to determine the size of other galaxy's/The dark matter problem

From what i understand there are two methods (well as far as i know) to determine how much mass there is in a distant galaxy. First, Luminosity. By measuring the amount of light produced from a ...
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Doesn't the presence of dark energy make the flatness problem less important?

If the cosmological constant (aka dark energy / vacuum energy) were zero, then an Omega greater than 1 would mean both positive curvature and a recollapse while an Omega less than 1 would mean both ...
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1answer
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Is it possible for the universe to be already developed when the dark energy appeared and expansion started?

The main piece of evidence that supports Big Bang Theory is basically evidence that the expansion of the universe started long time ago (not necessarily from the begining of the universe). Is it ...
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Relation of General Relativity to Dark Matter and Dark Energy

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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Question of the scale factor $a(t)$ for the dark-energy, $\Lambda$, epoch

Just a quick question. I find a lot that the scale-factor $a(t)$ goes as $a(t)\propto{\exp(Ht)}$ in the $\Lambda$ dominated model, however, what I am specifically looking for is the exact scale factor ...
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Dark Energy Density Paramater For Unlimited Expansion

Suppose that the universe is dominated by matter and dark energy. Let $\Omega_m$ and $\Omega_\Lambda$ denote the respective relative density parameters. Given $\Omega_m$, what does $\Omega_\Lambda$ ...
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Matter and dark energy

So dark energy is the biggest thing in the universe, it keeps accelerating the expansion. But it's a constant so at some point there was a matter - dark energy equivalence. My question is how can you ...
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Does matter shrink due to energy radiation and does it have anything to do with dark matter and dark energy?

Is matter shrinking? Is shrinking the cause of concentrated dark matter that makes up matter moving from concentration to unconcentration. Does dark energy and expansion of the universe come from this ...
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G4v Gravity Theory: Why does this get rid of Dark Energy?

Earlier this year, Carver Mead of CalTech published a paper which seems to be garnering a lot of attention: http://arxiv.org/abs/1503.04866 http://www.npl.washington.edu/AV/altvw180.html http://...
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Why is the universe expanding while its components actually attract each other?

First of all, what's the difference between gravity & gravitation? Anyway that's not the actual question. If every matter attracts each other toward itself, then wasn't the universe supposed to be ...
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Gravitational constant, $G$, What if it is not Constant?

The question is on title; What if Gravitational Constant, $G$, is not constant? Let's skip all the local consequences if it would suddenly change, like asked here; Can gravitational constant be ...
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Why is the expansion of universe continuously increasing? [closed]

If our universe is expanding and the concept of the multiverse is true, then why is the rate of the expansion of the universe increasing? Surely it must decrease?
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1answer
301 views

Can Gravity be a repulsive 'push' from Dark Energy, rather than an attractive 'pull' from Matter?

Gravity makes things that are more dense fall. If we extrapolate this fact through the entire Universe, we can imagine Ordinary Matter falling more than Dark Matter, and Dark Matter falling more than ...
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How do radio signals contribute to gravity?

First, the inspiration for this question: I just read that it takes one hour to send a picture from the New Horizons space probe, to Earth. It also takes around 5 hours for that picture to reach ...
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Why does dark energy seem to push things apart? [duplicate]

Ordinary matter acts to slow down the expansion of the universe. That makes intuitive sense, because the matter is exerting a gravitational force, acting to pull things together. Moreover, dark ...
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2answers
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What evidence is there for additional dark energy coming into existence when space increases?

As I understand since cosmological constant is a 'constant' - increasing the space must generate additional dark energy that fills that space This does sound counter-intuitive to me, but I am sure ...
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Could observed accelerating expansion be an illusion based on distance?

The thought occurred to me that if we just happened to be born into a time when the the universe started slowing down, it would take some time for us to observe this - especially in more distant ...
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Can dark energy be converted into energy source? [duplicate]

Dark energy is an unexplained phenomena. But can it be used as a energy source?
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146 views

Does the density of virtual particles decrease when space expands due to dark energy? [closed]

I understand that vacuum (i.e. QED vacuum) is theorized to contain spontaneously appearing and annihilating pairs of virtual particles. Suppose the average density of those particles at a given moment ...
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3answers
253 views

How does dark energy allow the universes expansion to accelerate?

I was wondering how dark energy is effecting the rate at which the universes expansion occurs.
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52 views

Does space expansion change value when traveling near the speed of light?

To draw an analogy, we receive roughly the same amount of cosmic background radiation from all directions. However if we were to travel near the speed of light relative to the reference frame where ...
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Dark Energy and Wormhole stability

Is it possible that the "negative energy" needed to create stable wormholes as theorized by Morris and Thorne (?) could be dark energy? Could this be the "exotic" negative energy matter referred to?
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Gravitational waves in general relativity

After reading some concepts of general relativity,is it true that the universe communicate with its different constituents (stars, galaxies, etc...) via gravitational wave? If so, how is that? Do ...