wrote:
How to measure the size of Universe!
http://www.studyandjobs.com/universe_size.html
This article is a litany of misconceptions. First sentence:
The current, observable universe has been determined to have a width of
156 billion light years, with an error of less than 1%, by the latest
deep-space telescope WMAP.
The widely-reported figure of 156 billion light years derives from a lower
bound on the size of the whole universe, not an estimate of the size of the
visible universe. Most of the news articles got this wrong.
Second sentence:
At first, it might seem impossible that scientists are so sure of this
astronomical measurement, but this figure has been narrowed by years of
research and determined by several paths of inquiry.
No, it hasn't. This figure is unique to one paper (astro-ph/0310233), and
was based on a single line of attack (looking for matching circles in the
WMAP data).
Skipping a bit:
We can only possibly look or communicate up to the edge, or "horizon," of
where light has traveled since the beginning of the universe.
It's where light has traveled from, not where it's traveled to, that
determines what we can see. In the usual Friedmann-Robertson-Walker
cosmology, the universe is infinite in size and there's light everywhere.
That doesn't change the fact that we can only see a finite part of the
universe. And this has nothing to do with how far we can communicate,
whatever that means.
The size of the universe means the space in which we can interact with
anything.
Maybe, but that has nothing to do with the size of the visible universe. You
don't seem to understand the difference.
We will never ever know what is "beyond" this boundary, because there is
no way to know anything about it, so it's illogical to consider the realm
"outside" of our universe, or to wonder what we are expanding "into."
Presumably you read somewhere that it's meaningless to ask what the universe
is expanding into. That's talking about the fact that there's nothing
outside the spacetime manifold. It has nothing to do with the particle
horizon (the farthest place we can possibly see now), nor the cosmological
event horizon (the farthest place we'll ever be able to see).
I suppose you're trying to be helpful by writing this article, but all
you're doing is spreading misinformation. Can't you write about a subject
you're personally familiar with?
-- Ben
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