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Quality answers to common cosmology questions
Jun25-11 08:50 PM bcrowell 

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Cosmology

- The origin, evolution, structure and eventual fate of the universe.
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To have an enjoyable cosmo forum we needed a balance between mental freedom on the one hand and a shared knowledge...
Apr8-14 08:39 AM
Jorrie
483 125,152
The new A20 tabular calculator lets you look at changing geometry out to about 88 billion years according to the...
Feb8-14 08:31 AM
mfb
61 23,397
So two of the theories of the universe are the big rip and the big crunch or bounce. Big crunch being expansion of the...
May21-13 11:10 AM
Mordred
2 778
Why didn't the big bang just become a black hole? Thanks, Jake
May20-13 08:55 PM
brianhurren
51 8,047
I don't know whether this has much general interest. I am interested by communication horizons in cosmology, or causal...
May20-13 11:31 AM
Chalnoth
11 875
Regarding the creation of the universe and the current model: Is it assumed that the universe, at the time of...
May20-13 01:10 AM
marcus
19 1,398
Hi there Am to teach a lesson on stars and galaxies to my year 7 class on Monday... Want to brush up on a few...
May19-13 11:11 PM
Chronos
8 748
By quantitative cosmology I mean with real times, distances, expansion rates, horizons, CMB stationary observers etc ,...
May18-13 12:36 PM
Mordred
13 813
Hi all, It is my understanding that a Doppler shift is the result of a change in wave frequency due to a change in...
May18-13 05:56 AM
mfb
1 572
I'm not a big fan of quintessence, but, this paper is interesting - Quintessence with Hybrid Potential,...
May17-13 01:35 AM
Chronos
0 590
I have been watching Susskind's lectures on Cosmology which are great. There is something that I can't wrap my head...
May16-13 08:57 PM
marcus
4 735
The basic equation of GR has a curvature constant Λ on the lefthand (geometric) side. The Friedman equation is...
May14-13 12:08 PM
Mordred
12 968
Everyday I sit and think about the universe, and after some thinking I always end up letting my imagination run wild...
May14-13 09:08 AM
Forensics
6 1,186
Where is the edge/boundary of the universe may sound like a simple question but I can see 3 possibilities. 1...
May13-13 05:09 PM
Spourk
133 7,423
There's a tutorial wiki for Jorrie's calculator. It needs exercises that beginning learners can do to help them get...
May12-13 01:36 PM
marcus
7 773
Quick question: is there a general formula for the redshift zC for a photon travelled in a spacetime with arbitrary...
May10-13 06:11 PM
George Jones
52 3,788
I tried out the new version of Lightcone today...
May10-13 03:45 PM
marcus
8 965
In a sense the universe is its own clock and the pointer-hand is the scalefactor, as in: "when distances were 0.1...
May9-13 05:18 PM
Mordred
10 1,097
I was trying to find an updated view on the plausibility of the Big Freeze. I believe that a couple of years ago, it...
May9-13 06:57 AM
bapowell
2 897
Is it possible for technology to advance such that we can travel back in time and be the ones to set the universe into...
May8-13 05:13 PM
Vanadium 50
4 841
The first stars formed when distances were 9% of their present size. The solar system began forming when distances...
May8-13 12:21 PM
Mordred
20 1,207
Developing a basic explanatory manual for the Light cone 1.0 calculator. This is as a supplement to give a basic...
May6-13 01:52 PM
Mordred
1 574
Hi. I read due interest papers in Arxiv. There is many times refereed to so called N-Body Simulations. Is that...
May6-13 10:25 AM
phyzguy
3 616
http://www.youtube.com/watch?v=VZiWKmhuaZE At about 7:00 he talked about imaginary time. Does that account for...
May5-13 09:24 PM
Simon Bridge
1 747
When the universe was young, and everything was closer together, did the extra gravity cause time to run slower than...
May5-13 05:48 PM
petm1
20 1,804
Einstein discovered that general covariance allows his GR equation to have just TWO gravitational/geometric constants:...
May4-13 03:32 PM
marcus
5 837
My question is what sort of material/matter existed to allow an expansion of the early universe? It had to be some...
May4-13 03:00 PM
spark802
8 785
It seems as though the contemporary consensus among cosmologists is that the universe is basically flat and Euclidean:...
May4-13 02:11 PM
WannabeNewton
33 1,848
Where did scientists reach so far about this matter? Any who had rejected it?
May4-13 05:11 AM
M. next
11 911
Here is a new paper, and thorough discussion of dark matter: Non-Baryonic Dark Matter in Cosmology,...
May3-13 07:24 PM
Chronos
6 700
So if there are as many galaxies in the Universe as is claimed what's the role of interstellar combination of light...
May3-13 07:18 PM
Chronos
6 271
(c^4/(8 pi G))*3*(17.3e9 light years)^(-2) Paste that in the google window, and see what you get. When I paste...
May3-13 05:12 PM
marcus
9 798
Hi I rarely have a background in physics (yet!) But based on my popular knowledge I understand that the Universe...
May3-13 04:40 PM
marcus
3 665
A new paper appeared on the arxiv today suggesting this possibility: http://uk.arxiv.org/abs/1305.0498 I would not ...
May3-13 10:32 AM
Mordred
3 671
New release of Jorrie's tabular calculator....
May2-13 08:40 PM
Mordred
4 778
Hello everybody! This is my first post! I was wondering about the fact that we have measure our universe to be flat...
May2-13 01:47 PM
vattoman
11 961
The medium gravitational potential must have been higher in the past than today (assuming constant mass/energy and an...
May1-13 12:47 PM
Mordred
7 886
Experience and conventional wisdom say that whenever there is a really good idea ready to makes its entrance it often...
May1-13 11:39 AM
Mordred
76 9,635
Since Omega-lambda is very close to Omega-matter, what could it mean if we assume they are exactly equal to each...
Apr30-13 05:40 PM
ftr
7 913
I'm interested in the history tables other PF members are getting as they try out Jorrie's online tabulator. What's...
Apr30-13 05:13 PM
Mordred
26 1,927
How can a black hole have a high entropy state if the matter inside it is in a supercondensed form with maximum...
Apr30-13 01:25 PM
jambaugh
14 1,061
"Normal" matter makes up about 5% of the mass/energy content of the universe. From studying this 5% we have discovered...
Apr30-13 12:55 PM
Haelfix
2 618

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