See light that is red-shifting z > 5.4

[Ich]

It depends on the coordinates you choose. What you have to do is to account for space curvature, where circumference/radius != pi. You may either scale the circumference or the radius in your coordinates, but you can't have both be "proper" coordinates if space is curved.
In http://en.wikipedia.org/wiki/Friedmann–Lemaître–Robertson–Walker_metric#General_metric", you scale the radius, and that is what the book does. You have to unscale r to get proper radial distance, but you can use r*dphi directly to get tangential proper distance.
In Hyperspherical coordinates, you scale the circumference, and r measures proper radial distance.
I almost exclusively use hypersherical coordinates, so there's no ambiguity between r now and proper distance now.

 

[granpa]

So we can see light that is red-shifting z > 5.4 which means it would be moving faster than light speed away in relation to us. How can we see this? We couldn't see the object's light while the distance between us is increasing at more than light speed right? I realize the light we are seeing is billions of years old but having a z of more than 5.4 doesn't make sense to me. The only thing I can figure is that the space fabric itself is expanding while the light is traveling through it elongating the light more than when it started. Could anyone shed light on this. I feel really bad for making that pun.

cosmic microwave background is at z = 1100

 

[niceboar]

cosmic microwave background is at z = 1100

Yeah. But apparently light observed currently around 5.4 will reach us redshifted to infinity, so it won't. The cosmic radiation background would account for objects physically impossible to get light from anymore.

 

[mrspeedybob]

One simple way to understand why Hubble constant is decreasing: consider galaxy 1 Mpc away. It is receding from us at 71 km/s. Now, if value of Hubble constant remains the same, once it is 2 Mpc away it should be receding at 142 km/s, and so on. Our universe is accelerating in expansion, but not all that much.

Let me see if I understand this. 1Mpc away an object would be moving away at 71 km/s due to the expansion of space. 1 billion years from now a different object 1 Mpc away would be moving away at a lower rate, <71 km/s. Does this value ever go to 0 or <0?

 

[Calimero]

Let me see if I understand this. 1Mpc away an object would be moving away at 71 km/s due to the expansion of space. 1 billion years from now a different object 1 Mpc away would be moving away at a lower rate, <71 km/s. Does this value ever go to 0 or <0?

Yes, that is correct. In empty (or near-empty) universe it would approach 0 as $$t\rightarrow\infty$$. However in acclelerated expansion model, it should approach asymptotic value around 60.