Are the Galxies Expanding?

[Rhondazvous]

I was reading Isaac Asimov’s book How Did We Find Out About the Universe. He says scientists noticed the star Sirius was red shifting. This goes against my understanding of the raisin bread dough model of universal expansion. According to what I understand of this model, the d ark energy acts as a kind of yeast while the space between the raisins/galaxies is the dough. Just as yeast doesn’t make the raisins expand so dark matter doesn’t infiltrate galaxies causing them to expand.

But if Sirius is red shifting that means intra galactic expansion. I always thought of dark energy and gravity acting like oil and water—not mixing. But if dark energy can defeat the gravity that holds the galaxies together, what keeps it from infiltrating atoms and defeating the weak force that holds atoms together? This is scarier than a renegade higgs boson playing around in a false vacuum.

I first knew Asimov as a science fiction author. But he was also a scientist and professor and has written many books expounding real science to young readers. This lends weight to what he says here.

[Gawdzilla Sama]

Or Sirius has a high velocity relative to the galactic center than us.

[Little lunch]

Or in a couple of hundred years, people laugh at how primitive we were, thinking that the galaxies were expanding. :-)

[Gawdzilla Sama]

Nah, a bunch of meat sacks on a tiny planet circling a mundane star in a somewhat larger than average galaxy residing in a typical supercluster of galaxies has already figured everything out. Nothing left to learn, or we would have already learned it.

[brewer]

I've got no clue. Just nice to see ya around more Rhonda.

[Brian37]

Yea welcome back Rhonda, we missed you.

[Jackalope]

Redshift is not necessarily indicative of expansion - expansion works on larger scales. What causes redshift between within in our galaxy is relative motion. Stars can have unusual trajectories, etc. It's not a result of the same phenomenon

[Rhondazvous]

Yea welcome back Rhonda, we missed you.

Well, you've had plety time to practice your aim.
(You knew somebody was going to say that)

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Redshift is not necessarily indicative of expansion - expansion works on larger scales.  What causes redshift between within in our galaxy is relative motion.  Stars can have unusual trajectories, etc.  It's not a result of the same phenomenon

He didn't use the term redshift. He just said the star is moving away as an example of universal expansion. But then, he also said Andromeda is moving closer. The man just messed me all up. My understanding is tore up from the floor up.

[Jackalope]

Andromeda is moving closer because it and our galaxy are gravitationally bound and are in mutual orbit - on those scales gravity overpowers the pressure of DE. Same with stars. DE works on intergalactic scales where distance between objects precludes any kind of significant gravitational interaction.

Simply, other, stronger forces are at work here that aren't elsewhere.

[Gawdzilla Sama]

Try keep in mind that the universe is actually orbiting around a certain politician's ego.