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Cosmology

- The origin, evolution, structure and eventual fate of the universe.
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Quality answers to common cosmology questions
Jul23-14 11:07 PM Greg Bernhardt 
Meta Thread / Thread Starter Last Post Replies Views
Jan16-12 Greg Bernhardt
To have an enjoyable cosmo forum we needed a balance between mental freedom on the one hand and a shared knowledge...
Jul25-14 06:02 PM
marcus
492 159,746
The new A20 tabular calculator lets you look at changing geometry out to about 88 billion years according to the...
Jun11-14 11:00 AM
Jorrie
65 41,563
The energy 'U' of a uniform spherical volume (e.g., a Hubble sphere) is (3/5)(M^2)G/R Conventional wisdom has it...
T 12:20 AM
yogi
14 555
If our universe has a history of infinity of cause-effects/time, how could it ever traverse that infinity to reach...
Y 02:02 PM
marcus
26 3,497
"In physical cosmology, cosmic inflation, cosmological inflation, or just inflation is the exponential expansion of...
Y 09:14 AM
phinds
23 1,285
hi, studying BSc astronomy/physics 3rd year in the UK on part time basis. i am a senior cosmetic dentist by...
Jul26-14 09:55 AM
marcus
2 325
Is it still true that most if not all galaxies have at their center a Black Hole? And that the estimated gravity is...
Jul26-14 09:13 AM
phinds
11 832
It is thought that there are approximately 10^80 protons in the observable universe, but there are approximately 10^90...
Jul25-14 06:22 PM
mfb
6 2,109
In general, what's a good way to understand the structure of the universe? I'm especially curious about the nature...
Jul23-14 06:38 PM
dgjohnsonstein
51 2,801
As far as i understand the current big bang theory, it started as a extremely dense object, finite in size. But we...
Jul23-14 06:29 PM
Student100
4 402
Hi all. Say we have a background inflaton field ##\varphi## and that we've integrated the background equation for...
Jul22-14 10:39 AM
WannabeNewton
9 852
I'm getting a rough idea of the holographic principle relating the shannon entropy of a boundary surface to the...
Jul21-14 05:34 PM
Chalnoth
3 656
I'm a physiologist, not in anyway well-versed in physics beyond what I took as a pre-medical student. Forgive any...
Jul21-14 03:16 AM
Matterwave
7 783
Hi, My question is: Whats the whole point of solving the Boltzmann equation for relic density of dark matter? I...
Jul20-14 03:48 AM
shahbaznihal
5 870
Why does it make more sense to imagine so much dark energy and dark matter to make things work (cosmologically...
Jul20-14 12:30 AM
Chalnoth
3 864
I'll try to develop some notation and explanations that might make the Friedman equations more intuitive to some...
Jul17-14 02:02 PM
marcus
21 4,230
Since dark energy and other models for explaining accelerating universe (which is quite hard to explain) are somewhat...
Jul16-14 05:04 PM
yogi
16 2,036
Hi everyone. I am not a physicist or scientist but this is a question I have pondered for a while now. Everytime I...
Jul15-14 10:42 AM
PeterDonis
3 1,419
These questions applies to both spatially homogenous cosmological models, and multidimensional Kaluza-Klein theories:...
Jul15-14 04:57 AM
center o bass
0 1,058
Hello guys, I was watching video about physical basis for arrow of time.. ...
Jul14-14 01:36 PM
Chronos
2 3,555
I've often read posts where the conservation of energy is questioned regarding redshift due to expansion. The question...
Jul14-14 01:34 AM
Lino
18 2,864
Does the existence of the "Axis of Evil" observed by WMAP and Planck mean that there is a special frame of reference...
Jul13-14 04:02 PM
Evo
10 1,686
T (Gy) R (Gly) 0.00037338 0.00062840 0.00249614 0.00395626 0.01530893 0.02347787...
Jul13-14 12:32 AM
Jorrie
38 6,532
I'm trying to sketch out what empty space is composed of and I'm drawing a blank (pun intended)....
Jul12-14 08:08 PM
DiracPool
6 1,791
Could you please confirm my idea of how to deal with the problem question in the attachment? In case of a...
Jul12-14 02:12 PM
Chalnoth
3 1,612
I thought this was an interesting article. I wondered does it create issues for the isotropic homogeneous view of the...
Jul11-14 11:30 AM
Chalnoth
5 1,475
Looking at the huge clumps of higher elements (carbon silicon iron etc) present in our solar system, it seams as...
Jul9-14 03:06 PM
Chronos
3 1,645
As far as I know, the main argument for the statement that the universe is expanding is that the velocities of...
Jul9-14 02:24 PM
marcus
17 2,866
Suppose you have a universe where Ω_{Λ}=1 and the rest are zero. Then the Friedmann equations are: ...
Jul9-14 10:36 AM
George Jones
7 1,504
Universe is expanding. I know that all the galaxies are getting away from each other due to the expansion. So in...
Jul9-14 10:14 AM
bapowell
7 467
Hello all, thank you for taking the time to read this post, i appologise if it is in the wrong section, as i am new...
Jul8-14 08:45 PM
AgentSmith
20 3,335
In multiverse cosmological models, what sort of infinities are usually used? For instance, in many models is it...
Jul8-14 06:09 PM
PeterDonis
7 805
Hi, I figured out a thought experiment/problem, here it is: A friend of mine is living in a galaxy far away. He...
Jul8-14 05:08 PM
Andrev
7 504
I have been reading about rotation curves, and the I understand the basics, but I am trying to understand the basis /...
Jul8-14 03:31 PM
Lino
10 1,219
I understand that 'roughness' in the universe is explained by inflation, because quantum fluctuations in density get...
Jul8-14 11:41 AM
kw1
8 750
I found an equation relating hubbles constant and time!It is highly simplified but helpful! ...
Jul7-14 01:39 PM
marcus
2 405
Why didn't the big bang just become a black hole? Thanks, Jake
Jul6-14 03:11 PM
PeterDonis
55 11,715
Hi, I am a research student in Theoretical Dark Matter Cosmology. I am currently working on the evolution of dark...
Jul5-14 07:33 AM
shahbaznihal
2 778
Does anyone have a reference to a site plotting the cosmological recessional velocity over the time span from the...
Jul4-14 06:34 PM
yogi
4 599
If size of the sun is increased million times ( trillion times or gazillion times), keeping its mass same and then the...
Jul4-14 06:44 AM
Bandersnatch
13 1,356
I mean the universe as some mass, energy, what does it matter if our local universe is curved or flat, when the...
Jul4-14 12:22 AM
Chalnoth
2 880
I know some folks may get tired of questions about the finite/infinite scope of the universe. Sorry for that. But as...
Jul3-14 08:07 PM
Lino
32 2,862

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