How far away is Andromeda Galaxy really?

Factual Questions
21

(This post refers to Universe expansion as understood before the recent concept of dark energy etc. That latter is still somewhat unproven and the matter of it’s effect on things is yet to be established. So everything I will be saying is from the “classical” Big Bang theory point of view.)

  1. The stuff in the Universe are not being pushed apart. Repeat: not being pushed apart. The atoms of a coin in your pocket are not being pushed apart. The atoms in you are not pushed apart. The atoms in the Earth are not being pushed apart. The planets of the Solar System are not being pushed apart. The stars in the Milky Way are not being pushed apart. The Galaxies in a cluster or supercluster are not being pushed apart. Galactic superclusters are not being pushed apart.

Is this clear to everybody?

Grab a bunch of pebbles. Throw them. Notice how the pebbles are moving apart. Notice, however, that there is no force pushing them apart. Their motion is is based on how they initially started and nothing more. Especially note that since there is no force pulling them apart, the individual pebbles are stable and not being split apart.

The Universe differs in certain ways from the pebble analogy. From the view of each “pebble” in the universe, it’s not moving and space is being created between the pebbles. This increase in space is not a force. Nothing is pushing on anything.

So:

  1. Galactic clusters and superclusters were just Very Large Pebbles that formed early in the history of the Universe and stuck together while they were hurled thru space. (Or, more like space being hurled away from them.)

(3. Regard dark energy and all. Take that coin out of your pocket. Hold it by the top edge over the ground. Note that the bottom edge is being pulled down by gravity. Why doesn’t the coin break up and fall into the ground? Because the electrical forces holding the coin are far stronger than the gravitational force. Ditto galactic clusters and dark energy. Gravity is far too strong and they are not being pulled apart.)

22

While the location of Andromeda has changed a bit over the past 3 million years, its current position doesn’t matter because we can’t ever get there “now”. The soonest we could ever get there would be in 3 million years, if we were to go the speed of light. Because of the finite speed of light as the ultimate universal speed limit, the concept of “now” is arbitrary and depends on the viewpoint. “Now” Andromeda is in the location we observe it because that’s where its light shows where it is, and that’s all that really matters.

23

I hate to admit this but I read the OP wrong and so even if I’d have known what I was talking about it still would have been screwed up. :smack: But sometimes you learn by making mistakes and I hope this is one of those times. :wink:

24

I thought everything really was being tugged at such that it feels some pull away from everythig else. It’s just that the expansion of space has an unmeasureably small effect on the attraction of one thing to another except on vast distance scales.

If the rate of expansion of space contitues to accelerate, even atomic nuclei will eventually start to “feel” it. Quarks won’t even be able to hold on to one another.

That’s a long, long, long way off, though.