
#19
Jun2804, 07:08 PM

Astronomy
Sci Advisor
PF Gold
P: 22,793

by Niel cornish] and some other people http://www.physicsforums.com/showthr...969#post244969 there you will find an arxiv link to the paper and also to a BBC popularization article IIRC, and also a link to Niel Cornish website his 24 gigaparsec is a "radiuslike" figure so you double it to 58 gigaparsec to a "diameterlike" thing and convert parsecs to lightyears and get 156 billion LY. It didnt turn into 156 billion LY until he started talking to reporters and taking interviews it is pretty abstruse, good luck trying to understand Niel's writing. the main thing is it is a MINIMUM size figurethe U could be flat and infinite and that is kind of the simplest picture but if it is finite then it has to be AT LEAST what Niel says, or we would notice it curving aroundhe and his buddies looked for signs of it curving around in the CMB and were able to rule it out for anything smaller than what he says 



#20
Jun2804, 07:30 PM

P: 608

We know so little about the universe I don't know how you could make a good guess. But I guess we have to start somewhere... I'd say the universe is 20+ billion years old.




#21
Jun2904, 12:40 AM

Emeritus
Sci Advisor
PF Gold
P: 10,424

WMAP, among other experiments, has determined the universe is 13.7 billion years old. We don't have to guess.
 Warren 



#22
Jun2904, 01:21 AM

Astronomy
Sci Advisor
PF Gold
P: 22,793

mainstream professional cosmologists are nearly all using the same model of the universe and these days they have arrived at a broad agreement on the observational data to plug into the model the error bounds have been narrowed way down so you take the model, which is two Friedmann equations, and you take the data (which since 1998 they are generally very confident in) and put the parameters into the model and it tells you lots of stuff: like the age is 13.7 Up until the mid 1990s the field was much more vague and there were people saying things like the universe is 20+ old, like you said just now. But mainstream people dont say that any more because it doesnt make sense. Of course it is your privilege to believe a very fringe thing like 20+ we can all believe what we want. but since your taxes support the cosmology profession and they have finally agreed on some basic things about the universe I would advise you to at least try to understand what they are saying and why they are so sure about 13.7 first understand the Friedmann equations, which are nice and simple, and then disbelieve if you are inclined towards nonconformism. no one can blame you if you understand what you are rejecting 



#23
Jun2904, 05:57 AM

P: 4

Kurdt & other friends,
The source from which I got the info is space.com http://www.space.com/scienceastronom...ay_040524.html As I understand our universe is like a bubble and our three dimensional space is the surface and the thickness of the bubble. From the illustration shown with the article, 156 BLight Yeras is the width or diameter of the universe. 



#24
Jun2904, 06:06 AM

P: 4

You have just touched the very core of my question. With your argument the question that arises is If the universe was at a single point 13.7 BLY ago, then how two points in the universe got seperated by say 43 BLYs in 13 BLYs? 



#25
Jun2904, 06:30 AM

Sci Advisor
P: 1,047

First note that when talking about the radius of the observable universe a proper distance is meant. This is the distance between us and our particle horizon measured with a rod today (which is obviously unphysical according to special relativity). Consider a radial photon beeing sent from our location at the time of bigbang. The location of the photon at each time is our particle horizon. If it were no expansion of space, then the distance today between us and our particle horizon would be indeed 13.7 GLyr. But since space is expanding behind the particle horizon (between us and the photon) during this 13.7 Gyr, the proper distance between us and our particle horizon (after 13.7 Gyr) will be greater than 13.7 GLyr. The actual distance depends on the cosmological model (in general it depends on Omega_matter, Omega_Lambda and the Hubble parameter). Regards. 



#26
Jun2904, 07:20 AM

P: 4

to have travelled faster than light? i.e. More than 13.7BLYs distance in 13.7BLYs. 



#27
Jun2904, 07:33 AM

Emeritus
Sci Advisor
PF Gold
P: 4,975

Here, I believe it is important to note that Einstein's premise that nothing travels faster than light was not broken since the space ITSELF expanded and not matter travelling through it. We can use the inflating balloon analogy for this. Two points on the surface increase their distance from one another as the balloon expands, but neither point on the surface moves at all, it is the space expanding that moves them apart and therfore any matter embedded in spacetime does not violate this dictum.




#28
Jun2904, 07:56 AM

Sci Advisor
P: 1,047





#29
Jun2904, 03:01 PM

P: 250

http://www.sciencemag.org/cgi/conten...304/5675/1226b 


Register to reply 
Related Discussions  
age and size of the Universe  Cosmology  9  
Size of universe?  Cosmology  9  
Size of the Universe  General Astronomy  7  
Size of the Universe  General Astronomy  10  
The size of the universe  General Astronomy  2 