Expert: Ed - 4/10/2005

Question
Hi. Can you help? I want to know where the Milky Way is located in the universe? For example, are we near the middle or near an edge?

I'm a bit confused because I'm watching a space documentary and they said that 'red shift' is observed by all the galaxys scientists can measure and so forth. And a scientist on the doc. said that in the universe everything is moving away from everything else. However, if the universe is expanding, shouldn't some galaxiese we can see being moving toward us and indicate a blue shift? If the universe is expanding outwards then to say everything is moving away from everything else doesn't take into consideration that some things are moving 'toward' other things does it?

Thanks if you could clarify these issues for me.

Answer
Stefan,

These are interesting, thoughtful questions.  Thanks for asking them.

Your first question is related to a topic which astronomers call "cosmology."  It is difficult to answer directly, because of the way that you phrase it.  Basically, you need to understand that the universe does not have a "middle," and it doesn't have "edges" either.  Therefore, the Milky Way is not in either of those regions, because those "regions" don't really exist.

The universe does not really have a "middle" or "edges."  This is similar to asking another question, which some people have asked me.  That question is "In what direction was the Big Bang?"  People want to know if they are looking in the direction of the Big Bang if they look toward Orion, or the Big Dipper, or whatever.  You need to understand that the Big Bang happened EVERYWHERE.  At that time, the word "everywhere" was only a tiny, tiny, tiny dot, but it was literally ALL of space.  That dot WAS everywhere.  Today, the universe itself is expanding, as it has been doing for 13.7 billion years, since the Big Bang.

I think you might like Ned Wright's Cosmology Tutorial.  It's pretty amazing, and it answers lots of these questions.
http://www.astro.ucla.edu/~wright/cosmolog.htm

As for your second question, yes, you are right.  That's pretty perceptive of you, in my personal opinion.  not many people think this through to that extent.  Basically, yes, there are a few galaxies with blue shift, but only a few dozen.  The overwhelming majority of galaxies do exhibit red shift.  

I once saw your question answered on another astronomy question service, so I'm going to connect you to that link.  Look down near the bottom of the webpage, for a link to a list of galaxies with blue shift.
http://www.physlink.com/Education/AskExperts/ae384.cfm

I hope this is helpful.  Keep Looking Up!
--Ed