Are the Galxies Expanding?

[bennyboy]

No, all the stuff in the Universe is shrinking.

[Gawdzilla Sama]

No, all the stuff in the Universe is shrinking.

https://en.wikipedia.org/wiki/He_Who_Shrank

[robvalue]

I don’t understand enough about it to say, but here’s that awesome song. Monty Python seem to think so.

[polymath257]

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.

According to this: https://en.wikipedia.org/wiki/Sirius, Sirius is current *approaching* the sun at about 5.5 km/s, which would mean it has a *blue* shift.

[bennyboy]

Red shifting is just the doppler effect-- if a star is moving away, its spectrographic spikes shift toward red. It doesn't necessarily imply a general expansion, unless a collection of bodies are ALL red-shifted-- which they mostly are. Pretty much everything we observe seems to be red-shifted.

[Jackalope]

Red shifting is just the doppler effect-- if a star is moving away, its spectrographic spikes shift toward red.  It doesn't necessarily imply a general expansion, unless a collection of bodies are ALL red-shifted-- which they mostly are.  Pretty much everything we observe seems to be red-shifted.

Except objects in our local galaxy. Those are moving away or towards depending on their relative motion due to gravity. Other galaxies not gravitationally interacting with our galaxy, sure.

[Gawdzilla Sama]

https://en.wikipedia.org/wiki/Redshift

[bennyboy]

Red shifting is just the doppler effect-- if a star is moving away, its spectrographic spikes shift toward red.  It doesn't necessarily imply a general expansion, unless a collection of bodies are ALL red-shifted-- which they mostly are.  Pretty much everything we observe seems to be red-shifted.

Except objects in our local galaxy.  Those are moving away or towards depending on their relative motion due to gravity.  Other galaxies not gravitationally interacting with our galaxy, sure.

"Unless a collection  of bodies are all  red-shifted."

[Gawdzilla Sama]

Like Hubble noticed?

[bennyboy]

Like Hubble noticed?

Yes, exactly like that.  Or, more precisely-- that.