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Early Light, Galaxies, and Big Bang
Name: Richard
Status: other
Grade: other
Location: NV
Country: N/A
Date: N/A
Question:
Scientists believe that the universe is around 14 billion
years old, give or take. We are able to look into the past using
telescopes, in which we are able to see, according to the Hubble
Ultra Deep Field images, the way the universe looked 13 billion
years. But the image shows galaxies that look completely formed,
and not in the process or forming. None of these deep space images
shows a primordial universe, with structures that should later have
formed into galaxies billions of years later. My question is, do these
images of well formed galaxies from 13 billion years ago therefore
shed doubt on the Big Bang theory, and if not, why not, and why
are we unable to view a primordial universe when looking back in time?
Replies:
Howdy Richard,
Indeed, we do look back in time by observing objects father away.
I think most of the objects in the Hubble Deep Field are around
12 billion years in age. This would give them a rather long time to
develop after the big-bang. There are images where objects older are
observed, for instance in the Hubble Ultra Deep Field (HUDF).
The HUDF images appear to observe galaxies that were already forming
within the first billion years after the big bang. Indeed, many of
these galaxies do appear to be quite young in character when compared to
other, closer galaxies. There are a few surprises, for instance finding
galaxies that appear slightly older than anticipated. However, these
are most probably a chance for further explanation and refinement of the
existing ideas and not direct contradictions.
A discussion of this very topic, a "teenager" galaxy among a group of
"toddler" galaxies can be found at :
http://hubblesite.org/newscenter/archive/releases/2005/28/full/
This suggests that our ideas about exactly what was happening with
galaxy formation in the early universe need a little refinement, but not
a wholesale revision. The article itself mentions that interactions (or
even collisions) between new galaxies may well explain the presence of a
more developed galaxy amongst younger appearing ones. It's actually a
nice example of how science works.
Furthermore, the basic idea and predictions of the big-bang theory are
quite sound and robust. In short the big-bang theory predicts a
red shift that increases with distance, a cosmic background radiation,
and the relative abundance of Hydrogen and Helium in the universe. It
does all this with some rather simple ideas.
I suppose the other things to remember in all this, is that the
time scales involved are ones which we have difficulty fully
appreciating. A million years is a very long time for things to happen.
A hundred million years, a billion years, those are really huge lengths
of time.
best wishes,
Michael S. Pierce
Materials Science Division
Argonne National Laboratory
The deep field galaxies are small, close together, and irregular. They
are not equivalent to the galaxies that exist in the present time. A lot
of evolution and merging has occurred since the time of the galaxies imaged
in the deep field and ultra deep field pictures.
Some of the galaxies seen in the deep field photo are not so old because
they are not so far away. To get an idea of where things are, take a look
at the deep field picture posted at
http://nedwww.ipac.caltech.edu/level5/Deep_Fields/mirror/hdfn/.
This image map is rigged so that you can click on a galaxy in the
image and learn about its characteristics, including its red shift
"z" value, which correlates to its distance and age. (The bigger
the z value, the farther away the galaxy, and the sooner after the
big bang.)
You will note that all of the galaxies of recognizable classical shape
(spirals, ellipticals) are fairly contemporary. The really old stuff
(note, for example, a little smudge above one of the stars in the image -
a star in the lower left right next to a yellow spiral galaxy oriented
upper left-to-lower right - the smudge galaxy is to the right of the yellow
spiral galaxy and above the star, and has a z value of 3-4) is fairly
undistinguished. These are not the galaxies in our local group.
Richard Barrans
University of Wyoming
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Update: June 2012
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