Relative speed between galaxies

Hello,

as a layman I'm interested in the universe.

My question is:

If I shoot (by an imaginairy explosion) an imaginairy galaxy system X from
Earth into some direction into space with a speed that causes that galaxy X
having the same redshift as a galaxy B who's redshift suggests it's at a
distance of 13 Billion lightyears from Earth, will the relative speed
between galaxy X and galaxy Y be zero? Or is this a wrong way of thinking,
because galaxy X is MOVING THROUGH the expanding space while galaxy Y is
('stationary' in, and) PART OF the expanding space?

Regards,

Henk

To Henk

To become comfortable with the motion of galaxies distant from our own
Milky Way you begin with the motion of planets in our own neighborhood
and especially the retrograde motion of Mars.

http://alpha.lasalle.edu/~smithsc/As...retrograd.html

Retrograde motion is a consequence of the heliocentric motions of Mars
and Earth as we watch the orbit of our position change in relation to
the orbit of Mars going around the Sun.

If you become familiar enough with that heliocentric perspective,move
on to the next motion - the galactic orbital motion of the Earth /solar
system along with the rest of the local visible stars around the Milky
Way axis.In principle we know that the local stars are rotating about
the galactic axis because ,over time, they will change their
orientation to the remaining galaxies just as if we are on an enormous
carousel made of stars.

Designating the position and motion of galaxies to local stars and
consequently the true motion of galaxies to our own will rely on the
explosive supernova events and Ole Romer's insight on the correction of
position and motion due to finite light speed but unfortunately
astronomy is still stuck with the Newtonian celestial sphere format
expanded into relativistic homocentricity ,the 'every valid point is
the center of the universe' notion.

In message ,
writes

elementary stuff snipped.


Designating the position and motion of galaxies to local stars and
consequently the true motion of galaxies to our own will rely on the
explosive supernova events and Ole Romer's insight on the correction of
position and motion due to finite light speed but unfortunately
astronomy is still stuck with the Newtonian celestial sphere format
expanded into relativistic homocentricity ,

Whatever that means. And as opposed to what?

I'll be interested to see an informed answer, because I can't be the
only person who thought of the red shift as a Doppler shift due to the
galaxy receding, while the current view seems to be that it is due to a
"stretching" of space (sorry if this is simplistic or just wrong :-)
Time dilation of supernovae agrees with red shift measurements (see
http://adsabs.harvard.edu/cgi-bin/np...97AJ....114..7
22R&db_key=AST, for instance, which looks to me as if the red shift
is a measurement of a real speed. If so, Henk's imaginary galaxy would
have very low velocity relative to the other galaxy with high red shift.
Determining the true motion of _nearby_ galaxies will depend on
measurements of their transverse velocities, not supernova measurements.

BTW, it's good manners and standard practice - "netiquette" - to quote
some of the OP's text.
--
Boycott Jap whale killers
Mail to jsilverlight AT merseia DOT fsnet DOT co DOT uk is welcome.

Two Supernova events observed from Earth occuring in different parent
galaxies .Representing the distance of each supernova from our position
as 186 000 miles for each second ,the difference between actual
occurence of the supernova from the observed occurence against the
principle of rotation of the foreground Milky Way stars generates a far
more complicated picture for the relationship of galaxies to the
rotation of the foreground Milky Way stars and ultimately to each
other.

What provisions have you made for incorporating the change in position
due to the rotation of the local stars to the parent supernova
galaxies ?.Obviously,it is impossible to mesh observed occurence of
the supernova within their parent galaxies with the position they hold
to the continously changing foreground stellar reference ,if the
supernova events are observed simultaneously but actually occured ,say
100 million years apart,it stands to reason that the local Milky Way
stars will have rotated roughly 180 degrees differently from one
supernova actually occuring to the other.

Newton mangled the Roemerian Equation of Light upon which all this
depends with Keplerian motion therefore there will be no progress on
the extremely difficult task of beginning modelling the motion of
galaxies to the Milky Way and to exch other.

"PH=C6NOMENON V.
Then the primary planets, by radii drawn to the earth, describe areas
no wise proportional to the times; but that the areas which they
describe by radii drawn to the sun are proportional to the times of
description.

For to the earth they appear sometimes direct, sometimes stationary,
nay, and sometimes retrograde. But from the sun they are always seen
direct, and to proceed with a motion nearly uniform, that is to say, a
little swifter in the perihelion and a little slower in the aphelion
distances, so as to maintain an equality in the description of the
areas. This a noted proposition among astronomers, and particularly
demonstrable in Jupiter, from the eclipses of his satellites; by the
help of which eclipses, as we have said, the heliocentric longitudes of
that planet, and its distances from the sun, are determined."

http://members.tripod.com/~gravitee/phaenomena.htm

I assure you that supernova data as representative of parent galaxies
and against foreground rotation is an extremely productive avenue once
the Newtonian celestial sphere is dropped .I wrote an outline two years
ago and this is just recycling the same procedure.

In message ,
writes
Two Supernova events observed from Earth occuring in different parent
galaxies .Representing the distance of each supernova from our position
as 186 000 miles for each second ,the difference between actual
occurence of the supernova from the observed occurence against the
principle of rotation of the foreground Milky Way stars generates a far
more complicated picture for the relationship of galaxies to the
rotation of the foreground Milky Way stars and ultimately to each
other.

What provisions have you made for incorporating the change in position
due to the rotation of the local stars to the parent supernova
galaxies ?

What on Earth does the rotation of galaxies have to do with their
cosmological red shift?


Newton mangled the Roemerian Equation of Light upon which all this
depends with Keplerian motion therefore there will be no progress on
the extremely difficult task of beginning modelling the motion of
galaxies to the Milky Way and to exch other.

"PH=C6NOMENON V.

snip

Don't you ever get tired of repeating this? Just what does the
retrograde motion of planets have to do with the rotation of galaxies?

I wrote an outline two years
ago and this is just recycling the same procedure.

Citation please.
--
Mail to jsilverlight AT merseia DOT fsnet DOT co Dot uk is welcome.

Jonathan Silverlight wrote:
I'll be interested to see an informed answer, because I can't be the
only person who thought of the red shift as a Doppler shift due to the
galaxy receding, while the current view seems to be that it is due to a
"stretching" of space

We had a thread on this a year or so ago. The upshot seems to be that
the latter is a better way to think about things, but for "real work"
there is no substitute for plugging into the correct equations.

Time dilation of supernovae agrees with red shift measurements (see
http://adsabs.harvard.edu/cgi-bin/np...97AJ....114..7
22R&db_key=AST, for instance, which looks to me as if the red shift
is a measurement of a real speed.

No, it comes out the same either way. Redshift is redshift, and all
clocks are affected the same. Specifically, an "atomic clock" that
produces a spectral line is affected the same way as a "supernova
clock" based on the SN light curve.

If so, Henk's imaginary galaxy would
have very low velocity relative to the other galaxy with high red shift.

Let's see whether I remember the original question... If you could
mount your instruments on a rocket and fly at high speed towards some
distant galaxy, you could pick a speed such that its redshift would be
zero. You would then see a SN light curve in that galaxy decay at
normal rate, and the galaxy's measured redshift would be zero
regardless of what spectral line you picked to observe.

Steve Willner