What is the current radius of the observable universe?

[heusdens]

Originally posted by marcus
Hi heusdens, it is a nice try but doesn't work

I am replying to what you said in previous post:
"But what if our length unit would be choosen in such a way, that it does express some fundamental property of nature. As I suggest, the expansion of space itself, ..."

You have been given a bad misconception from popular accounts and the careless way astronomers talk

The rate that space is expanding is different in different places.
It is uneven.
Uniform expansion is not at all a "fundamental property" of space built into its nature.

When they talk about the expansion rate they mean a kind of temporary average.
The average is only strictly correct for the present moment (t=0) which is why they write the zero subscript on H₀.

And it is only a rough estimate gotten by averaging the expansion in various places and directions from us, which rigorously speaking are all different.

The main equations of cosmology---Friedmann's two equations---are boiled down from Einsteins by ASSUMING that the distribution of energy in space is isotropic and homogeneous (same everywhere and in all directions) which it obviously is NOT.

However the Friedmann equations are simple and terribly useful and the work soooooo well! Even though predicated on obviously false assumptions. These equations contain the definition of the Hubble constant----the idealized expansion rate.

We have enough to worry about with the fundamental constants we already have. Please do not suggest that the expansion-rate of space is also a "fundamental constant"!
Compared with other things it is highly changeable.
One should really call it "Hubble parameter" (as some people are starting to do) and not call it Hubble "constant."

But cheers anyway, I sympathize with your interest in scales of measurement and foundations-issues

That's a good point!

And there is one other thing about the Hubble correlation parameter.
We can only observe this correlation in a very tiny spatial and temporal extent (namely: the temporal and spatial extend in which we know about, or since we do scientific cosmologic observations).

How do we know then that there is a distance - velocity ("virtual" recession speed) relation, it could as well be a time - velocity / virt. reces. speed relation.

 

[meteor]

For me, the answer is 14 billion y.l. And look what says Alan Guth, the creator of the theory of inflation:
"We find that the universe is expected to be at least 10 to the power of 23 times larger than the observed universe. If the inflationary theory is correct, then the observed universe is only a minute speck in a universe that is many orders of magnitude larger"

 

[heusdens]

Originally posted by meteor
For me, the answer is 14 billion y.l. And look what says Alan Guth, the creator of the theory of inflation:
"We find that the universe is expected to be at least 10 to the power of 23 times larger than the observed universe. If the inflationary theory is correct, then the observed universe is only a minute speck in a universe that is many orders of magnitude larger"

Alan Guth worked out his own version of what is called inflation, based on an idea of the Soviet scientist Starobinsky, end of the '70-ies. This model, about a large scale transformation of matter in the universe, was however too complicated, and in fact did not work.
But it has lead to new attempts, for instance by Alan Guth and others. There have appeared a number of ideas in that field, for instance that of eternal / chaotic / open inflation by Andrei Linde.

 

[Michael F. Dmitriyev]

All contradictions withdraws if take as a basis the law of conservation of Time Cycle of objects (universe in particular). In this case the universe can enlarges, in the same way can compresses. These phenomenas can be as global , in the same way can be as local. It is possible to present universe as a complex system with automatic regulation.