Tagged Questions
4
votes
2answers
66 views
Cosmological triangle with PLANCK results
Is there an updated version of the cosmological triangle with recent PLANCK results included?
0
votes
3answers
80 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?
4
votes
1answer
71 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
73 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) = ...
5
votes
4answers
284 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
82 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 ...
-2
votes
1answer
179 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
2answers
132 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?
2
votes
1answer
64 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 ...
0
votes
1answer
116 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 ...
1
vote
2answers
192 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
216 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 ...
2
votes
2answers
152 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 ...
0
votes
1answer
123 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
1answer
134 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
3answers
146 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
252 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 ...
0
votes
1answer
74 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 ...
0
votes
2answers
139 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?
3
votes
0answers
49 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
150 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 ...
1
vote
2answers
63 views
proportion of dark matter/energy to other matters/energy at the beginning of the universe
How will the proportion of dark matter/energy to other matters/energy be like at the momenets after the beginning of the universe (standard Big Bang model)?
0
votes
1answer
126 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
180 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 ...
7
votes
2answers
206 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
2answers
255 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 ...
4
votes
2answers
262 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), ...
1
vote
0answers
175 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 ...
-3
votes
2answers
143 views
Could dark matter be expanded atoms, and dark energy expanded radiation?
After watching Lawrence Krauss' lecture 'life, universe, and nothing', an interesting idea lighted up in my mind. Is it possible that dark matter is just spread out matter waves and dark energy ...
4
votes
1answer
386 views
When will the Hubble volume coincide with the volume of the observable Universe?
The Hubble volume is the volume that corresponds to objects so far from the Earth that the space between us and them is expanding faster than the speed of light. (I.e. objects outside this volume ...
16
votes
3answers
604 views
Are modified theories of gravity credible?
I'm a statistician with a little training in physics and would just like to know the general consensus on a few things.
I'm reading a book by John Moffat which basically tries to state how GR makes ...
6
votes
4answers
306 views
Dark matter references
I've been looking for questions about dark matter, and I've read some very interesting answers. However, I desire too look into it deeply.
This is not actually a question. I'm asking the community ...
3
votes
2answers
222 views
asymptotic curvature of the universe and correlation with local curvature
There is not-so-rough evidence that at very large scale the universe is flat. However we
see everywhere that there are local lumps of matter with positive curvature. So i have several questions ...
12
votes
5answers
390 views
What experiments, other than Hubble Expansion, support the Dark Energy theory?
Dark energy is introduced as a constant inside Einstein's equations. Its primary purpose, from what I understand, is to make Einstein's equations compatible with the accelerating expansion of the ...
4
votes
3answers
302 views
What current alternatives are there to the standard concordance model of cosmology?
The current "standard model" or concordance model of cosmology is Lambda CDM which includes late time acceleration due to a cosmological constant, cold dark matter as the missing matter component and ...
