Not only do I not “dig” but I can’t make any sense out of what you have said.
Can you please explain (non-math) how “space expands and moves objects apart” but “the expansion of space doesn't actually make objects "move”.” (don’t know why the quotes).
Okay, ynot, fair enough. I goofed a little. Before I explain my goof, let's start from the beginning, just to be sure. This time, I'm going to pull out all the stops. This is my last card to play, the final showstopper, the ultimate answer, the explanation to end all explanations.
It's time...for the
over-extended analogy (pun intended)...
Let's start with a simple universe: you, me, and a rubber sheet. We each stand on an end of the rubber sheet. We each take out a big marker, and mark a big ol' "X" right under our feet.
Let's examine the difference between peculiar motion and space expansion...
Case #1: Peculiar motion. Startled, you take off running away. After awhile, you stop. I call out to you: "Ynot, have you moved?". You respond, "Yes, Frank, I have. The big X-mark is no longer under my feet. I have very clearly moved!" While you were running away, I recorded your image. Indeed, I noticed you had a redshift, and it matched my calculation of a Doppler effect. Thus, your motion caused a Doppler shift. You knew that you had moved, because you no longer were on top of the big X-mark.
Case #2: space expansion. Our devious friends pull on the ends of the rubber sheet, without us knowing. Jerks. Both of us notice that the other is getting smaller and smaller and getting farther and farther away. Worried, you call out to me, "Frank! You are getting farther away! Are you moving???" I reply: "Sorry, ynot, but I am not! The big X-mark remains solidly under my feet. So, I am not moving! What about you?". "The same for me, I'm afraid," you respond, "my big X-mark is right there, all big and X-ey. I can confidently say that I am not moving!"
So what gives? We are getting farther away, but each of us is reporting that we are not moving! Indeed, as we examine the light from each other, we notice a redshift, but that redshift does not agree with calculations from a Doppler effect. So the expansion of space
does not make us move!
The expansion of space makes us farther away from each other, not by making us move, but by
making more space between us. The light, on its way from you and me, was redshifted not from Doppler effects, but because as it was traveling along, space got more stretched out, which made the photon itself stretch out...a cosmological redshift!
So the lesson is this: the expansion of space creates the
illusion of motion; the
illusion that galaxies are "flying" away from each other. But the galaxies are
not moving, there is just more space between them. This is why I put "move" in quotes earlier: because it
looks like the galaxies are moving, but it's really just space expanding. The expansion of space does not "push" galaxies away from each other...there is just more space between the galaxies. The galaxies
are farther away from each other, just like you and me were farther away. But not because they moved (they still see a big X under their feet), but because there is more space!
There! That's the best I can come up with! I think I know what you're struggling with, and it's the following statement I put: "space expands and moves objects apart". That was very sloppy on my part, and I am very sorry. I'm a sloppy guy! It should read: "space expands and objects are farther apart". With cosmological expansion, there is no "pushing" or "pulling" or "moving" or "flying"...there is
just more space.
I really hope this did the trick! If not, my apologies.
Cheers,
TV's Frank