I'm interested to know the formula of the redshift used in cosmology, and what distance predicts for that quasar with z=6.4
Also, I wanna know if is true that the radius of the observable universe is 42 billion y.l.
Thanks

Lucas - you might want to post this for the physics geeks...

:m: Peace.

http://arxiv.org/PS_cache/astro-ph/pdf/0111/0111061.pdf

Thanks for the link, (Q), but the formula that Carmeli gives don't include a cosmological constant, so I think that the formula is not correct

Try out the cosmos calculator (http://www.earth.uni.edu/~morgan/ajjar/Cosmology/cosmos.html). For the formula, it's probably within Ned Wright's Cosmology Tutorial (http://www.astro.ucla.edu/~wright/cosmolog.htm).

When I put values {.3, .7, 70, 50000} into the calculator, it says 45 billion ly for the radius of the observable universe (the distance of an object which is now at the edge of the observable universe).

It seems to me we are running in to more and more contradictions in
the currently accepted (by most astronomers) BB theory.
Less than a year ago it was published on this forum -and other sites -
that the universe was exactly 13.7 billion years old. (Not withstanding that most asronomers agree that many stars in globular clusters are very old,14 to 15 billion years).
If we accept zanet's estimate of a radios of 45 billion LY for the universe (and I have no reason to disagree with that) it would mean that the light we receive from the edge of the universe took 45 billion years to reach us. Ergo the universe must be 45 bilion old ? ?

It's getting curioser and curioser as Allis said. Personaly I think we are tying ourselves up in knots by trying to fit all the latest discoveries in to the old BB theory. Anyone for a new theory ?

APOLO

PS. I have no doubt some one will call me cracpot after reading this.

It’s greater than 13 billion ly to the edge of the observable universe, because while the light from an object that is now at the edge was on its way to us, the universe expanded in size.

Have a friend hold one end of a piece of slightly stretched taffy. You hold the other end. Imagine a spider walks along the taffy from your friend to you while you & your friend stretch the taffy. By the time the spider makes it to you, it will appear that it walked farther than it did if you measure its distance traveled from the end that stretched away from you as the spider walked. The spider didn’t really walk that far.

With light it’s an even more believable illusion, because the light shows you the distant object which really is that far away at the moment the light hits you. But like the spider, the object wasn’t that far away from you when it emitted the light.

The distance to the edge of the observable universe is a function of both how old the universe is and how fast it has been expanding.

ZANKEK. The first paregrahf of your last post is obviously corect,so if your estmate in the previous post of 45 billion light years as the radius of the universe is right then the universe must be larger than at least 90 bilion LY. Or possibly infiniteli large

APOLO.

Originally posted by zanket


Have a friend hold one end of a piece of slightly stretched taffy. You hold the other end. Imagine a spider walks along the taffy from your friend to you while you & your friend stretch the taffy. By the time the spider makes it to you, it will appear that it walked farther than it did if you measure its distance traveled from the end that stretched away from you as the spider walked. The spider didn’t really walk that far.


Hello Apolo and Zanket, the image of the spider running over the stretching taffy is a good one. It could help get over the confusion about light traveling in expanding space.

There is a new pedagogical article that tries to identify some of the confusions and how to get over them. It was just posted on arxiv within the past couple of weeks, by Tamara Davis and Charles Lineweaver. It is called "Expanding Confusion"

It is by two cosmologists, and it has some diagrams, and is a sincere effort to clear up very natural confusion, but I am not sure that they come up with anything that is really better than the spider on the taffy.

Your figure of 45 billion LY is just about right as the current radius of the observable U---the present distance of the most distant point from which light could be reaching us. If you look up Davis and Lineweaver article you will see that distance in their space-time diagrams, that show the past light-cone.

In case anyone wants it, I went and found the link

http://arxiv.org/astro-ph/0310808

but it basically just confirms what you say about the spider and the 45 billion LY (even tho the age is just 13.7 billion years or so)