Talk:Particle horizon

message: I did a bit of heavy editing.  There were a few factual inaccuracies (or fuzzy statements), for example
* what was defined previously was not the conformal time but the change in conformal time, 
* the particle horizon is only equal to the conformal time when we're measuring it in comoving distance (otherwise there is a factor of a(t))
* conformal time doesn't describe a universe that is expanding (this is the job of the metric, which can use the c.t. as one coordinate)
* the article seemed to suggest that just because the overall scale of the universe is expanding, then there are no horizons, which is false.
Also it wasn't really clear why things had to be a list.  Anyway, I hope that the edits kept the sense and intention of the original information.  If you don't think so let's talk and come up with a better solution.  Wesino 18:59, 23 November 2006 (UTC)
thread_title:  Major edits 

message: I'm concerned about our event horizon definition, which right now reads --
:while the event horizon is the largest comoving distance from which light emitted now can ever reach the observer at any time in the future.
I don't think that "now" really has any meaning in this context as there is no simultineity in GR, so it seems this def could be cleaned up.  Wesino 22:20, 5 May 2007 (UTC)
replies: text: This article ist about the event horizon really, because the particle horizon describes the distance, objects can be influenced by us in the future. Our event horizon is thus the particle horizon of objects in the past we can observe. Ra-raisch (talk) 23:56, 15 March 2022 (UTC)
thread_title:  event horizon defs 

message: Of course, I'm sure its me but I failed to see any (estimated) numerical value for the particle horizon.  Hence my conclusion that this article needs work.  If you didn't answer the question any 6 year old would ask (namely "but how far IS it?") then you probably aren't being very helpful to most people (and are directing your writing towards the geeks).  —Preceding unsigned comment added by 69.40.243.166 (talk) 21:28, 2 February 2008 (UTC)
replies: text: Eebster the Great (talk) 18:07, 18 March 2008 (UTC)
thread_title:  geeks  =

message: Generally, I found it very odd to land here from the Dark Flow page (this is linked from its 3rd paragraph) and to be almost immediately faced with a wall of mathematics that are unclear to a poor layman who would find this indecipherable. It might help to either include a link to a main article explaining the particle horizon in more general terms or to expand this article with an opening section. To clarify a bit, the Dark Flow article states a Particle Horizon of 46 billion light years. Given the Universe is ~14 billion years old, there's a 32 billion light year gap to leave the public scratching their heads over. The article as it stands does nothing to resolve such confusion. 86.46.117.189 (talk) 13:11, 8 June 2014 (UTC)
replies: text: I've added a contents box with a lead-in before it that should clarify this point - the 32 billion light year gap comes from the expansion of the universe, so that we use the conformal time rather than the age of the universe to work out the particle horizon. In other words light travelling for 14 billion years actually travels a lot further than just 14 billion lightyears (which it would if the universe was static). HannahFord428 (talk) 09:55, 5 August 2014 (UTC)
thread_title:  Layman explanation lacking? 

message: The page says the conformal time today is 1.48*10^18 a bit down the page. But this value is dependent on the Hubble constant. It makes sense to put also the Hubble constant value that the person that has put this value have used. This because there is still large uncertainty in the value of the Hubble constant. This so the page do not cause confusion when students finds other values in books etc. But ball park the value is correct, it is just one need to tell what Hubble constant value is used to get it.ChrisCalif (talk) 09:37, 23 May 2021 (UTC)
replies: text: I thought the error bars on the Hubble constant are about 10%, so its not that large. Anyway, this calculation also assumes FLRW and perfect fluids, and avoids inflation, so there are lots of caveats to interpreting it's result. Although the result could be explained more carefully. 67.198.37.16 (talk) 17:21, 6 June 2021 (UTC)
thread_title:  What Hubble Constant? 

message: The particle horizon today is 14.4 Gpc, and that of recombination is 284 Mpc which is 1.9722E-02 of 14.4 Gpc.
However, 8.9E-03 is written in the equation, which would be a typo.
If possible, I would like to learn how the particle horizon values of recombination and today are determined. RetiredEng (talk) 13:48, 9 May 2023 (UTC)
thread_title:  The particle horizon of recombination