Chatroom
 

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Bad Astronomy and Universe Today Forum > Space and Astronomy > Astronomy
Register FAQ Members List Calendar Mark Forums Read

   

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1 (permalink)  
Old 27-September-2006, 10:01 PM
antoniseb's Avatar
antoniseb antoniseb is offline
Moderator
 
Join Date: Jul 2005
Location: Marlborough, MA
Posts: 14,979
Default Lensed Quasar Time Delay - Independent H Determination

Here's a paper that looks at 15 lensed quasars' time delays and comes up with a value for H of 70 +/- 3. This value is independent of the WMAP data, or similar measurements.

The paper discusses the outlook for studying many other lensed quasars to confirm that the value of H is the same in all directions, and to refine the value arrived at here.
__________________
Forming opinions as we speak
Reply With Quote
  #2 (permalink)  
Old 30-September-2006, 01:42 AM
folkhemmet folkhemmet is offline
Banned
 
Join Date: Mar 2004
Posts: 286
Default closing in on Ho

It is interesting how the spread in values for the hubble parameter has been shrinking over the years. Few groups are still getting results of Ho in the 50s, but many more groups are getting results in the 70s. Even Sandage et al, a proponent of a lower value for Ho, recently published a paper which put Ho at 62. So I think, unless some unlikely trick of nature or coincidence is at work, that the Hubble constant is almost surely between 60 and 80-- and probably right around 70.
Reply With Quote
  #3 (permalink)  
Old 30-September-2006, 03:18 AM
GOURDHEAD GOURDHEAD is offline
Senior Member
 
Join Date: Sep 2003
Posts: 2,169
Default

If the cosmological expansion accelerated 5 billion years ago, shouldn't there be different values for the coefficient of expansion before and after the beginning of the recent acceleration?
__________________
For those inclined to oppose human meddling with the structure of the universe or the composition and configuration of objects and groups of objects within the universe, consider:
Whether there is a limit to the magnitude of a modulation of chaos below which order remains invariant? Or, is order but a fiction invented by perspectives applied over finite, however large, time intervals?
Reply With Quote
  #4 (permalink)  
Old 30-September-2006, 03:26 AM
antoniseb's Avatar
antoniseb antoniseb is offline
Moderator
 
Join Date: Jul 2005
Location: Marlborough, MA
Posts: 14,979
Default

Quote:
Originally Posted by GOURDHEAD View Post
shouldn't there be different values for the coefficient of expansion before and after the beginning of the recent acceleration?
Yes. I'm not sure what the values are, but the older values of H would be smaller than the newer values by a few percent.
__________________
Forming opinions as we speak
Reply With Quote
  #5 (permalink)  
Old 30-September-2006, 02:25 PM
GOURDHEAD GOURDHEAD is offline
Senior Member
 
Join Date: Sep 2003
Posts: 2,169
Default

Are our instruments good enough to detect other variations of the coefficient of expansion that may have ocurred prior to 5 billion years ago?
__________________
For those inclined to oppose human meddling with the structure of the universe or the composition and configuration of objects and groups of objects within the universe, consider:
Whether there is a limit to the magnitude of a modulation of chaos below which order remains invariant? Or, is order but a fiction invented by perspectives applied over finite, however large, time intervals?
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT. The time now is 06:14 AM.


Powered by vBulletin® Version 3.7.3
Copyright ©2000 - 2008, Jelsoft Enterprises Ltd.
LinkBacks Enabled by vBSEO 3.0.0
©  2006 Bad Astronomy and Universe Today