Galaxies

Post by **peter** » Sun Oct 22, 2017 12:11 pm

Why are they shaped like disks rather than spherical? Why do they spin around the central black holes that gobble them up rather than just pour into them, and do they all spin the same way and if so why? Does the universe spin as well?

Post by **Vraith** » Sun Oct 22, 2017 1:38 pm

Not all of them are disk-shaped. Rotation and gravity and momentum are the cause of diskification [[I'm pretty sure, not positive, that all clusters will either drift apart and end up in other galaxies OR not and then have a disk-phase. Collisions between galaxies also stir things up a bit]]....and conservation of motion/momentum plus the shape of space keeps everything from diving straight in.

Galaxies just don't all spin the same way.

I have heard differing opinions on whether the universe as a whole rotates.
Never really looked into it, just did a quick search, and it seems still unresolved.

Post by **Wosbald** » Mon Oct 23, 2017 2:04 am

+JMJ+

Vraith wrote:I have heard differing opinions on whether the universe as a whole rotates.
Never really looked into it, just did a quick search, and it seems still unresolved.

How would that even make sense? Rotating in relation to what?

Post by **peter** » Mon Oct 23, 2017 7:17 am

That was my thought Wos when I posted, but I had an inkling that I'd heard or read that it might. I wondered whether the spinning of galaxies was caused by quantum irregularities in the fabric of space-time going back to the big-bang, but did think that collisions between objects might play it's part. But somehow, probably because the 'plughole' effect of material in chaotic motion around a hold through which it is passing is so ingrained in us, it just feels right that that is how it should be played out on the Galactic scale. But 'It feels right' ain't enough in science ...... you gotta say how!

Post by **Vraith** » Mon Oct 23, 2017 3:59 pm

Wosbald wrote:+JMJ+

Vraith wrote:I have heard differing opinions on whether the universe as a whole rotates.
Never really looked into it, just did a quick search, and it seems still unresolved.
How would that even make sense? Rotating in relation to what?

Heh, I don't know...I said I hadn't really looked into it.
That seems a similar question to: if space is expanding, expanding into what?

But it also seems to me there might be ways in which it could be rotating in relation to itself, internal motion states/relationships.

Imagine, if you will, that you are a nitrogen molecule inside a rapidly rotating and inflating balloon---but that you have no knowledge of the balloon/edge, cuz you can't "see" that far.
You could still detect the rotation through relations with other gas molecules within the sphere.

That only works, of course, if the balluniverse isn't, in a strange sense, "solid."

And it can't be a normal kind of rotation like the balloon...cuz there is no "center" around which it is rotating...

And it's no less confusing if you try to visualize through the standard analogy where one isn't "in" the balloon, but on the stretching/inflating surface...
Even in that case, though---if the balluniverse were rotating, and wasn't "solid"--or at least inflexible-- [[which it seems it can't be, if it is stretching/expanding...]] then there SHOULD be detectable "twisting." And this would be in relation to itself, its "internal" state/motion/structure.

And...perhaps...the math of relativity provides an empirical lens through which we could observe the twisting. If you're looking at the relative motions/positions of two or more very distant objects the results will be different in a turning balluniverse than a non-turning one...
But how much precision do we need in measurement? If it was rapidly rotating, not very much [relatively speaking]...but the slower the turn, the more difficult to detect...what if the turning only causes a nanometer of difference over tens or hundreds or millions of light-years?

[[or maybe relativity is, in part, an outcome/effect of the rotation---though that gets even weirder, and is a leap across a giant gap to even imagine, let alone show a causal/physical justification for]].

Just improvising out of my mental butt with all that...

Post by **wayfriend** » Mon Oct 23, 2017 5:45 pm

The universe can rotate relative to itself. For example, outer rings may be rotating faster than inner rings. Like that.

Post by **peter** » Tue Oct 24, 2017 6:46 am

The image of V. improvising out of his mental butt makes the thread worth it all on it's own!

Post by **Cord Hurn** » Wed Jan 23, 2019 9:12 pm

wayfriend wrote:The universe can rotate relative to itself. For example, outer rings may be rotating faster than inner rings. Like that.

Makes sense.

Post by **Zarathustra** » Wed Jan 23, 2019 9:54 pm

Why the galaxies form 2D planes (or spiral-like) instead of 3D balls (or spherical-like)?

Post by **peter** » Thu Jan 24, 2019 3:56 am

Excellent link Z! Thanks for posting.

Post by **Skyweir** » Sun Jan 27, 2019 5:43 am

peter wrote:The image of V. improvising out of his mental butt makes the thread worth it all on it's own!

Post by **peter** » Mon Jan 28, 2019 9:22 am

Seared indelibly onto the hard-wiring of my innermost psyche Sky!

Post by **Vraith** » Mon Jan 28, 2019 5:57 pm

peter wrote:Seared indelibly onto the hard-wiring of my innermost psyche Sky!

It's all in the motion, my friend...the collisions, the momentum, the rotation.

WHICH, BTW [the rotation] is way the hell weirder/different from what WF said. Sure, parts within can move like some analogue of that...but the universe, as a whole, single entity, if it is rotating, is not rotating---cannot rotate---much like that.

Kinda like if you take a picture of a football and an actual football and start them spinning. They have practically nothing in common, and all the important stuff is different.

Post by **peter** » Mon Jan 28, 2019 6:33 pm

Well, you wouldn't want to blow that out of your butt - mental or otherwise!

Post by **Ur Dead** » Tue Mar 19, 2019 7:24 am

Well the closest your going to get with a 3D galaxy is the elliptical galaxy.
Some are pretty huge too. Like IC1101

Post by **peter** » Wed Mar 20, 2019 3:55 am

How big in lights years? The size of the Universe is still bugging me as well; I know the observable bit is 15 billion lys, but how far does it stretch on beyond that? I'm betting that is where all of the really interesting stuff is going on.

I'm heading out there for a look see once I get this small matter of life sorted out.

Post by **Skyweir** » Wed Mar 20, 2019 6:49 am

Can I tag along

be interesting to ... boldly go where no man has gone before

Always fantasised about trekking through the universe in the enterprise

Post by **Vraith** » Wed Mar 20, 2019 4:44 pm

peter wrote:How big in lights years? The size of the Universe is still bugging me as well; I know the observable bit is 15 billion lys, but how far does it stretch on beyond that? I'm betting that is where all of the really interesting stuff is going on.

I'm heading out there for a look see once I get this small matter of life sorted out.

Yea...that pesky speed limit.
BUT...the Visible is 15-ish. The OBSERVABLE is 46 in every direction, so diameter over 90Billion.
Beyond that...it gets weird

For instance, IF any of the models with a curved universe [which I think includes any model that ends with a "Big Crunch"] are correct, THEN the current size must be AT LEAST 15 TRILLION light years right now.

Post by **Skyweir** » Thu Mar 21, 2019 12:32 am

And whats beyond that?

Post by **peter** » Thu Mar 21, 2019 3:54 am

If I have it right, it's (or can be at least) mathematically consistent for it to be both infinite but still contained ........ something like a three dimensional version of a sphere's two dimensional surface.

V - can you just spin out a quick explanation of the difference between the visible and observable universe. I'd always thought that they were one and the same (hence my mistake on the size ).

Kevin's Watch

Kevin's Watch

Galaxies

Galaxies