1. what is the maximum known speed a galaxy at the edge of the universe moving and what is the maximum speed possible for a galaxy to attain.

2.

3. Galaxies do not “move” away from us. Galaxies do rotate and they orbit a central point in large groups called superclusters. Space itself is expanding so that the distance between galaxies is increasing and the more distant a galaxy is the faster it is receding from view. In the distant future, only stars in the Milky Way will be visible at night. Think of galaxies as raisins in a lump of dough. As the dough rises the distance between the raisins increase. Similarly, space is expanding but there is no galaxy marathon.

4. Originally Posted by Arch2008
Space itself is expanding so that the distance between galaxies is increasing and the more distant a galaxy is the faster it is receding from view. Think of galaxies as raisins in a lump of dough. As the dough rises the distance between the raisins increase.
I find that with many of the counter-intuitive concepts of physics, expansion velocities are one of the most difficult to understand.

An example, please correct me if I'm wrong:

We'll use a linear string of galaxies (A-Z) that are each 100 million light years from the next, whereas the rate of expansion between them is 100,000 mph. In other words, galaxy A will view galaxy B receding at that velocity.

A<--->B 100K mph

But, A will not view C or any other galaxy cluster in that string receding at that speed, but instead increases proportional to their distances. In my example, I use nice round numbers, adding them together for simplicity, where normally we would use the Hubble constant derivatives to measure.

Hence, A will view C and C will view A receding at 200,000 mph, as would A viewing D and D viewing A receding at 300,000 mph, and so on...

Each cluster will in turn view the exact same observations down either side of the string.

A<--->B<--->C<--->D<--->E<--->F<---G 100K mph to next cluster

A<----------->C 200K mph

A<-------------------->D 300K mph

So, if we are in cluster A and we are viewing cluster B, and they viewing us, we would agree the expansion rate between us is 100K mph.

However, if we are viewing cluster Z, and they viewing us, we can agree the expansion rate between us is 2.6 billion mph.

Corrections?

5. That is how I understand it as well.

6. G'day from the land of ozzzzz

People talk about expanding universe and expanding space and so on.

Is it really expanding?

Or do we really on the line of sight, ie observations. That show us that the parts that make up the universe group together and do not expand as a TOTAL.

Contraction occurs where there is a gravity sink. Eg Stars and so called black holes.

Expansion occurs during supernovae and jets from compacted matter such as Neutron stars and Black Holes.

7. FYI your post is AOK, Q. You addressed the Q&A’s of the A,B,C’s of expansion PDQ and to the point. A+

8. Originally Posted by Arch2008
FYI your post is AOK, Q. You addressed the Q&A’s of the A,B,C’s of expansion PDQ and to the point. A+
10-4.

9. G'day from the land of ozzzzz

Here down under we see 10-4 as 4-10

So people keep on talking about the Expanding universe.

10. Originally Posted by Harry Costas

People talk about expanding universe and expanding space and so on.

Is it really expanding?
Yes Harry, it is. That is what is observed.

It's important to understand the concept behind expansion as some confuse expansion with classical explosions. The above explanation would never occur under the conditions of a classic explosion, where instead of space expanding and carrying with it the objects - the object(s) themselves explode outwards. This is not observed.

11. What is the reason for expansion? Will there be any contraction in future?
Expanding universe will evade galaxy merging?

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