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4
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2answers
136 views

Cosmological triangle with PLANCK results

Is there an updated version of the cosmological triangle with recent PLANCK results included?
-3
votes
1answer
476 views

Could entropy explain dark energy? [closed]

This was 3rd beer idea, so please bear with me. What if the universe was not actually expanding but the speed of light was slowing? Wouldn't that be indistinguishable to our observations? Either way ...
0
votes
3answers
162 views

Acceleration in the rate of expanansion of the universe due to weakening gravity?

Could the acceleration in the rate of expansion of the universe be due to the weakening of gravitational forces, as the distance between objects continues to increase?
5
votes
1answer
468 views

How the CMB anisotropy is linked to the existence of cold dark matter and dark energy?

After the data from the cosmic microwave background has been collected by WMAP or Planck, what types of analysis is needed to conduct in order to deduce the cold dark matter density and the ...
6
votes
2answers
121 views

Why are *high redshift* measurements of supernovae required to measure dark energy?

Why are high redshift measurements of supernovae required... in order to measure the equation of state parameter of dark energy? The luminosity distance can be written as \begin{equation} d_{L}(z) = ...
-2
votes
4answers
204 views

Dark energy and dark matter [duplicate]

Our galaxies are speeding apart from each other and that is because of dark energy, but we don't know where it comes from right? If I'm not mistaken could dark matter have dark energy? (If they are ...
5
votes
4answers
740 views

Why is it important that the equation of state parameter of dark energy is measured?

The equation of state for a perfect fluid is that $p=\omega \rho c^{2}$, where $p$ is the pressure, $\rho$ is the density, $c$ is the vacuum speed of light, and $\omega$ is called the equation of ...
2
votes
0answers
164 views

Our Universe in collision with another one

This question is related to the possibility that there are many other universes in the UNIVERSE,the multiverse, that were created during collisions between membranes, according to string theories. The ...
-4
votes
1answer
769 views

Is antigravity the source of accelerating expansion (dark energy)?

Is antigravity the source of accelerating expansion(dark energy)? From the observation of 1998, we found that our universe has been continuing accelerating expansion, and the unknown cause for this ...
1
vote
1answer
57 views

Could there be a small-scale observation of dark energy?

The amount of dark energy in the universe is pinned down fairly precisely by fluctuations in the cosmic microwave background, if I understand correctly. So in that sense there's very good evidence of ...
1
vote
2answers
255 views

Is cosmic background radiation dark-matter and/or dark-energy?

Dumb question alert: Is it possible that the cosmic background radiation might be the source of dark-matter and/or dark-energy? What is the mass of the background radiation in the known universe?
0
votes
3answers
223 views

Black hole accretion of dark energy

Dark energy physically can be interpreted as either a fluid with positive mass but pressure the negative of its density (pressure has units of energy/volume, and energy is mass), or a property of ...
2
votes
1answer
63 views

Dark Energy and Conservation of Momentum

IF dark energy was not perfectly evenly distributed(as some theories suggest), in other words if some cubic centimeter had a very small difference from another cubic centimeter, would that imply that ...
2
votes
1answer
80 views

Dark energy before radiation or after?

In the cosmic history of the universe, does the dark energy comes before the radiation epoch, or only now, in the 'matter' universe (matter dominated era)? Because, we now know that like 75% of our ...
-1
votes
2answers
226 views

Is Dark Energy converted to Gravitational Potential Energy?

Dark Energy is basically doing work against gravity to accelerate the expansion of universe. So, for time-translational symmetry to be hold, dark energy must be converted to gravitational potential ...
2
votes
3answers
522 views

Less than absolute zero possible? [duplicate]

Possible Duplicate: Temperature below absolute zero? According to this article http://www.sciencemag.org/content/339/6115/52 (preprint: http://arxiv.org/abs/1211.0545) it is. What do you ...
2
votes
2answers
394 views

Dark matter and dark energy [duplicate]

Possible Duplicate: Dark matter references I have recently read about dark matter and dark energy, and why physicists think it must exist (dark matter: mass of galaxies are far bigger than ...
1
vote
2answers
250 views

Cosmology questions from a novice

These ideas/questions probably represent a lack of understanding on my part, but here they are: 1) Cosmologists talk about the increasing speed of expansion of the universe and talk of dark energy as ...
4
votes
1answer
121 views

Why is it desirable to have a symmetry to make cosmological constant zero?

It is sometimes stated that absence of a symmetry to make cosmological constant zero is a problem. But observed value of dark energy is very small and non-zero. So why is it desirable to have a ...
2
votes
2answers
289 views

Could dark energy be heat? Could dark matter be stuff that is not seen because of its refraction limits?

Heat has to go somewhere. Would the light and heat of the stars in the universe amount up to being dark matter ...and dark energy ... Dark matter would just be small pieces of stuff. Dark energy ...
4
votes
2answers
244 views

Dark Energy saving the world

Ok, my understanding of physics is still limited, hoping to change that in the following years, but I have a question. Dark energy is what provokes the expansion of the universe, so, in theory, it ...
0
votes
1answer
113 views

Why the world is so deep and dark?

We live in a dark world, and the light is results of big bang. The world is really made mostly of dark matter and dark energy? Why the world is so deep and dark?
0
votes
1answer
152 views

Is a new universe created when dark energy rips open a singularity?

Dark energy will tear everything apart, even black holes. Is a new universe created when dark energy rips open the singularity of a black hole ? And does the topology of the universe depend on the ...
0
votes
2answers
249 views

What are the differences between dark energy and a cosmological constant?

My possibly mistaken understanding is that dark energy changes with time, whereas a cosmological constant is, well, constant. What about gravitational clumping? Detecting relative motion?
4
votes
1answer
217 views

How much does electromagnetic radiation contribute to dark matter?

EM radiation has a relativistic mass (see for instance, Does a photon exert a gravitational pull?), and therefore exerts a gravitational pull. Intuitively it makes sense to include EM radiation ...
4
votes
3answers
220 views

Could dark energy be powered by force particles that obey quantum mechanics?

From what (little) I know about physics, I understand that the universe is expanding due to dark energy, and I understand that no one quite understands it yet. I also understand that the cosmic ...
2
votes
0answers
426 views

Is large-scale “time reversal” (Poincaré recurrence) possible given infinite time?

The following are some assumptions I'm basing my question on, from what (little) I understand of physics. I list them so an expert can (kindly) tell me where I'm going wrong. There is a probability ...
1
vote
2answers
126 views

Cosmological constant of standard model of cosmology and observational data

I am curious whether the current Lambda-CDM model of cosmology matches well with observational data, especially expansion of the universe. How well does Lambda-CDM defend its established status from ...
1
vote
2answers
183 views

Possibility of making dark energy equivalent with dark matter

I was curious whether it is possible to make dark energy equivalent to dark matter. Can this unification be done? If it can, why do scientists prefer to separate dark energy from dark matter?
5
votes
2answers
852 views

How is dark energy consistent with conservation of mass and energy?

I initially thought that dark energy must in some way violate conservation of mass and energy since the component of the energy density of space that comes from dark energy is constant, and space is ...
3
votes
0answers
50 views

squeezed radiation astronomy

Squeezed electromagnetic vacuum does have a renormalized energy density smaller than the vacuum. So it makes it in my opinion a inconspicuous candidate for a dark energy carrier. Are there ...
1
vote
1answer
278 views

What exactly are super WIMPs?

I recently got confused (and slightly annoyed by the lack of technical details) when reading a popular article (authored by Jonathan Feng and Mark Trodden) introducing the concept of super WIMPs. The ...
4
votes
3answers
123 views

Proportion of dark matter/energy to other matters/energy at the beginning of the universe?

What was the proportion of dark matter/energy to other matters/energy at the moments after the beginning of the universe (standard Big Bang model)?
3
votes
3answers
339 views

Theory that gets rid of dark matter/energy

Is there any physics theory that either groups together gravity and dark energy/dark matter or eliminates dark energy/dark matter by modifying standard understanding of gravity or any force? If so, ...
4
votes
2answers
612 views

How much light is there in space and how heavy is it?

Our night sky is filled with stars. On a dark night a significant fraction of the sky is light. This light, we are told, has been in transit for many millions of years. There must therefore be quite a ...
0
votes
1answer
144 views

Proportion of energy compared to mass in universe

In Wikipedia (http://en.wikipedia.org/wiki/Dark_matter), there is a picture that shows us the proportion of matter and energy in the current universe - CMB. It seems to suggest there is nothing that ...
1
vote
1answer
321 views

What allows us to infer the existence of dark energy?

A recent Indian examination asked: how do we infer dark energy is there? It gave as options: rotation curves of galaxies, accelerated expansion of the universe, existence of microwave background ...
5
votes
2answers
483 views

Is dark matter really matter?

Is dark matter really a form of matter? We know it has a gravitional attraction and we know that everything that has a gravitional force is made by matter. But maybe this is an exception? And if ...
8
votes
3answers
270 views

Why doesn't dark energy vary with time?

Trying to teach myself the basics of cosmology. I can see why, in an expanding universe, radiation and matter density, and radiation and matter pressure vary with time. But why is it assumed that dark ...
2
votes
1answer
87 views

Why do we need the concept of dark energy to explain the expansion of the universe?

Why can't the expansion of the universe be thought as the Big Bang itself still in progress? Why do we need to introduce dark energy? The Big Bang was powerful, and that explosion itself could still ...
5
votes
1answer
137 views

Can dark matter and energy be formulated as local perturbations of the metric

Note, my formal physics education ended over ten years ago so I may be missing some obvious piece of understanding. The relationship between space-time and matter/energy distribution is described by ...
2
votes
2answers
285 views

Why is it concluded that the cosmos is expanding when in fact the observations are for events further back in time?

Why is it concluded that the cosmos is expanding at an ever increasing rate when looking further out and therefore further back in time? Surely, if the time were reversed to play forwards, the ...
0
votes
2answers
217 views

Is existence of cosmic dark energy falsifiable yet?

Is "existence of cosmic dark energy" falsifiable yet? And what about dark matters? Let me rephrase it again(pardon me for my previous poor expression)- Is there any condition discovered which can be ...
1
vote
0answers
62 views

How many times brighter could the stars shine without raising the temperature of space?

If my understanding is correct, the temperature of space (as defined by the temperature that a black-body will reach) has been decreasing since the big bang. It has never increased. Additionally, ...
3
votes
1answer
439 views

Gravitational waves as dark energy?

Is the energy carried by gravitational radiation a viable candidate for $\Lambda$ / dark energy?
3
votes
2answers
131 views

“Dark” quantities

I don't know much about the so-called dark matter, apart from what has been described in popular descriptions of the reasons for it being postulated. My question is, is there dark momentum, dark ...
5
votes
3answers
375 views

Could the acceleration of universe expansion be caused by gravity itself?

Dark energy is suggested to be a repulsive force in the universe causing an accelerated expansion. If the amount of mass outside our observable universe is greater than inside (higher mass density), ...
2
votes
0answers
125 views

Dark-energy sources and respective implications

Firstly, I want this to be a very layman/simple level. According to Sean Carroll, we have certain possibilities for where dark-energy comes from: http://www.youtube.com/watch?v=v6o2bUPdxV0 ...
8
votes
1answer
35 views

New Type of Type Ia supernova. Implications to Dark Energy measurement?

As I understand it, we used Type Ia supernovas to determine that there is some sort of repulsive force (which we call dark energy) making things fly away from us at an accelerated rate. The reason we ...
2
votes
0answers
213 views

Why do galaxies collide? Reconciling dark energy and an expanding universe with the fact that some galaxies are on a collision course

My layman understanding of cosmology is: galaxies are uniformly (more or less) spread throughout the universe, per the Big Bang and the fact that in a central explosion, all dispersed points are ...