Expert: Tom Whiting - 9/7/2005

Question
My co-workers and I are trying to figure out this question.  If we are correct, we are assuming that all objects are moving away from the center of the universe.  We were under the impression that the fastest moving material is at the edges of the universe and that the slower moving material would be closer to the center of the universe.  If this is so, then under what circumstances does an object in the night sky show a blue shift toward the Earth?  We are all moving away from the center, but what could cause the speeds of the objects closer to the center of the universe to be greater than our galaxies speed?  Does it have anything to do with our position in our orbit around the sun, or in our solar system's position in its orbit around the center of our galaxy?  

Answer
Hi Debbie....
Very good questions, and I'll take them from bottom to top.
1.  Our position in space, the sun, the Earth, the Solar System,
even our Milky Way Galaxy, has nothing to do with any of
this expansion of space, which BTW, is now thought to
be accelerating rather than decelerating as we originally thought.  (And it is the space itself expanding, not the
contained matter- the galaxies are just along for the ride,
similar to an empty canoe going downstream in a river,
faster and faster).

You state...."We are all moving away from the center....

Debbie, there is no "center", any more than ants crawling
around on an inflated ballon have a center in their mind.
Think of it more as a baking raison bread in the oven,
and our galaxy is one of the raisons.....(any raison, as it does not matter-you'll see the same from any raison). As the bread
expands, the closer raisons (nearby galaxies, except for
the Local Group...see below) are receding....moving away......slower.  More distant raisons are moving away still faster, and the most distant raison is moving away the fastest (exhibits the greatest red shift).  And the bread is rising,
getting bigger, faster and faster, as time goes by.

So your original assumption is incorrect....there is no center.
Another reason there is no center.....we, and everything
else in our known visible Universe, is INSIDE the Big Bang....
we are all part of it, enclosed by it, and this is why any direction you observe, you are always looking backward in
time (Yes, a telescope can be thought of as a "time machine"); And the farther out we look, the further back in time we see, all the way to the initial Big Bang event. We can
never see the Universe, or Big Bang event, from "outside"
the Universe or Big Bang, because we are all part of it, on
the inside.
SO, we are not moving away from any center,  because there is no center to move away from.  So every galaxy exhibits a doppler Red shift or recessional velocity....EXCEPT......
Our Local Group of 30 odd galaxies....the Milky Way, the
Andromeda Galaxy (M-31), the Pinwheel Galaxy (M-33),
NGC 2403, and a collection of some 27 dwarf galaxies.....where local gravity over-rides the general expansion of space which is only 71 Km per second per Megaparsec  (sorry) the Hubble expansion constant....so a few of the Local Group galaxies are in fact approaching the Milky Way, thus they exhibit a rare blue shift...coming toward us.  (In fact, M-31 and the Milky Way will have a near miss or collision some 5-6 billion years from now.)
But the sun will swell into the Red Giant stage in about
3-4 billion years, so we won't watch the collison from this
planet as Earth  will not exist anymore, being swallowed up
by the giant sun.

But back to your questions...
No, the fastest moving objects are the farthest away from
us, and those are the galaxies that formed right after the
Big Bang.....I believe we....Hubble...can image proto-galaxies
that formed only about 500,000 years ABB (after Big Bang)
which occurred some 14 billion years ago.  (+ or - 0.5 billion
years).  And those are receding at a terrific recessional
velocity relative to the Milky Way...in fact, you'll hear the
terms UV dropout and visible light dropout...many of those
distant galaxies are actually redshifted down into the infrared
and radio part of the electromagnetic spectrum.  In fact the
remnant radiation from the Big Bang event itself, can be seen
in the microwave part of the radio spectrum, at 1.1 mm wavelength....discovered by Arno Pensias and Robert
Wilson- back in 1965 with their radio telescope.
(Google CBR - Cosmic Background radiation, if interested.)

So we (Milky Way galaxy) are not moving away from any
center, but rather, moving away from everything else, as
everything is moving away from everything....(except for
the Local Group which is gravitationally tied together)
and doing so, faster and faster. A billion years from now
the only galaxies we will see is the Local Group...the others
will have receded far into the distance so as to be not
visible to us any more.  A lonely, heat death ending, but
don't lose any sleep over it.....that won't happen for hundreds
of quadtrillion years from now....So actually, this Universe
just began about..."a month ago"....We, the Solar System,
formed up about 10 days ago (1/3 the age of the Universe) and humans have only existed a second or two....this "Experiment" has just begun.  And it has a long way to go.....in fact, the known visible Universe
is still 97% hydrogen (H) and helium (He) from the Big Bang event.....only 3% of our Universe is Lithium (atomic number 3) to Uranium (atomic number 92) - what astronomers call the 'heavy metals' or heavy elements.  (The heavies are
synthesized by nuclear fusion in the core of stars, and the
supernovae release the heavy elements into the original
H-He mix-that's where they come from).   So stop and think about that....and like me, you'll reach the conclusion that we're darn lucky to be here as early as we are....we hit the Big Lottery....how many other
"places" have a concentration of those 3% heavy elements...
the stuff we're made of...calcium, carbon, iron, etc.
Probably not very many...in fact, we could very easily be
alone in the Milky Way Galaxy, this early....in fact, we may
just be the first life form in the Galaxy.  Numbers of stars
(200 billion in the Milky Way) are meaningless if you don't
have the heavy elements....Many people play the Big Power
Ball Lottery, but there is only one winner per year, approximately.  So sheer numbers of stars, is academic in
this case...you have to have the proper raw materials
(heavy elements) present in abundance.

Oh, one other thing....you keep throwing out terms...faster,
slower.....realize velocity is all relative to some other object.
There is no such thing as "absolute rest"....when you are sleeping in bed, you are only stationary, relative to the
surface of the Earth.  But the Earth is rotating at 1000 mph
at the equator, relative to the center of the Earth;  The Earth is traveling at 18.5 miles per second
around, relative to, the sun.  The sun is traveling some
200 mps around the Galaxy, relative to the center of the
Galaxy, and the Galaxy is traveling about 600 mps relative
to the Virgo Supercluster, and it is probably moving too,
relative to something else.  So we are never back to where
we started, even after one year....we are always forging ahead, breaking "new ground" as we travel thru space.

Oh, one other thing....there is no huge galactic coordinate system either, as Star Trek would have you believe....both
your position and speed (velocity) are always relative to some other body.
When Capt. Kirk is tooling along in the Starship Enterprise,
with the starship Lexington far behind, and he says,
"Let's stop here and wait for the Lexington to catch up".....
what the heck does he mean by that? Let's analyze that
statement.

STOP?  stop, relative to what?  Everything is moving, relative
to everything else.....that Solar System off to our right,
perhaps?  You have to have another body so you can stop
relative to it....but you are still moving relative to any other
body.
HERE?  Where is here?  Here, is only relative to some other
body, at the same time...again, that Solar System off to our right?  But then you will have a different position relative
to any other body.
Star Trek wants you to believe that there is this huge
galactic coordinate system out there, and we can navigate
by it.....But it does not exist....so his original statement is
meaningless - non-sequitor...and only for your convenience and entertainment.

I know I've rambled here, but I hope all this helps you
understand the current thinking relative to spacial
orientations and velocities....if I've missed something, or
one of your questions, sorry....feel free to contact me directly
at
bwhiting@velocity.net   (no pun intended-velocity) ;-)
as I am retired USAF pilot and welcome student questions
about astronomy and cosmology.

Clear Skies,
Tom Whiting
Erie, PA

Please visit our club website for great pictures of my new
30 inch portable scope, at
http://www.velocity.net/~bwhiting/


FOLLOW UP....
Oh, historically, it is interesting to note that it was
Edwin Hubble that first announced, in 1924, that all
galaxies (except the Local Group) were moving away from
us....and then in 1929 he added, moving away
proportionally.....that is,  a galaxy 10 times farther away
is moving 10 times faster, and 30 times further away 30
times faster.....thus establishing the Hubble constant
of expansion of around 70 Km per second per Megaparsec.
But today we know it's not a true constant because
spacial expansion is actually accelerating  (not decelerating
as we once thought) so it's not a true constant, and
varies with time and perhaps distance.
FWIW,
Clear Skies,
Tom Whiting
Erie, PA