Author Topic: Why record the galaxy rotation?  (Read 17378 times)

GeoHani

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Re: Why record the galaxy rotation?
« Reply #15 on: August 26, 2008, 09:36:56 pm »
...so what we see as far galaxy structure CW, ACW and Edge On is just based on how the center (or core)  decided to start spinning? And for the next 13 million years this will not change? Thats a tough one for me to accept... I'm not saying I won't... just saying its tough.


FermatsBrother

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Re: Why record the galaxy rotation?
« Reply #16 on: August 27, 2008, 11:06:26 am »
...so what we see as far galaxy structure CW, ACW and Edge On is just based on how the center (or core)  decided to start spinning? And for the next 13 million years this will not change? Thats a tough one for me to accept... I'm not saying I won't... just saying its tough.
Hi GeoHani - A couple of points:

Who said that spirals originated 13 million years ago ? ::) ::)

"..decided to start spinning". ;D ;D
A fundamental question, which no-one seems able to answer for me, is what is the origin of the angular momentum in spirals ?
It is suggested that it's (elliptical) galaxies sweeping past each other, but I can't see that working.
I think that there's some other mechanism at work, which has yet to be discovered.

(BTW, if you start any object spinning in space, and there is no mechanism for it to loose the energy from the spin, it will spin forever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever & ever..... ad infinitum !! ;D ;D ;D)

Fermats Brother
« Last Edit: August 27, 2008, 11:13:47 am by FermatsBrother »
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GeoHani

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Re: Why record the galaxy rotation?
« Reply #17 on: August 27, 2008, 12:02:04 pm »
Quote
Who said that spirals originated 13 million years ago ?

I don't know... I didn't say that. I said for the next 13 million years they would continue unchanged :-)

Alice

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Re: Why record the galaxy rotation?
« Reply #18 on: August 27, 2008, 01:49:54 pm »
Isn't the origin of angular momentum just gravity and collapse? Imagine a massive cloud of hydrogen and helium, which eventually starts to collapse . . . you know those things in museums where you roll a ball towards a well, it goes round and round and round it first - because that's what everything does unless you aim it dead straight at the centre! Or would my argument mean that the spiral should collapse? Which as far as I know it doesn't, so my suggestion would be wrong.
« Last Edit: August 27, 2008, 01:58:03 pm by Alice »

FermatsBrother

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Re: Why record the galaxy rotation?
« Reply #19 on: August 27, 2008, 01:52:26 pm »
Quote
Who said that spirals originated 13 million years ago ?

I don't know... I didn't say that. I said for the next 13 million years they would continue unchanged :-)

Hi George - Such is the ambiguity of language ! ;D ;D
The context ("decided" = past tense) suggested to me that you meant 13 million years ago.
However, the argument still applies if the spiral was formed 13 million years ago, today or 13 million years in the future !

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FermatsBrother

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Re: Why record the galaxy rotation?
« Reply #20 on: August 27, 2008, 01:58:13 pm »
Isn't the origin of angular momentum just gravity and collapse? Imagine a massive cloud of hydrogen and helium, which eventually starts to collapse . . . you know those things in museums where you roll a ball towards a well, it goes round and round and round it first - because that's what everything does unless you aim it dead straight at the centre! Or would my argument mean that the spiral should collapse?
Hi Alice - If the "cloud of hydrogen and helium" had angular momentum before the collapse, then it would be preserved in the final (spiral) galaxy.
The problem is that in a "cloud of hydrogen and helium" there is no reason for it to have any angular momentum when you summate all the material.

It is generally accepted that galaxy rotation results from either "tidal torqueing" with another passing galaxy, or "galactic/satellite combination".

When you "roll a ball towards a well", you are applying a force (a torque) in a particular direction (because of friction) and inducing angular momentum.
If your ball wasn't on a surface, it wouldn't rotate! ;D ;D

FB
« Last Edit: August 27, 2008, 02:11:17 pm by FermatsBrother »
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Alice

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Re: Why record the galaxy rotation?
« Reply #21 on: August 27, 2008, 02:30:20 pm »
So if a cloud started to collapse, it wouldn't necessarily start rotating?

GeoHani

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Re: Why record the galaxy rotation?
« Reply #22 on: August 27, 2008, 03:53:44 pm »
...so a galaxy seen as 'edge on' will stay that way forever basically? Assuming a relative base of observation and no outside forces.

FermatsBrother

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Re: Why record the galaxy rotation?
« Reply #23 on: August 27, 2008, 07:42:58 pm »
So if a cloud started to collapse, it wouldn't necessarily start rotating?
Hi Alice - That's right. Where do you think the ellipticals came from ?

FB
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FermatsBrother

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Re: Why record the galaxy rotation?
« Reply #24 on: August 27, 2008, 07:44:50 pm »
...so a galaxy seen as 'edge on' will stay that way forever basically? Assuming a relative base of observation and no outside forces.

Hi George - Nicely observed ! With your criteria, (and no internally produced forces), that's right.

FB
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Alice

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Re: Why record the galaxy rotation?
« Reply #25 on: August 27, 2008, 07:54:55 pm »
So if a cloud started to collapse, it wouldn't necessarily start rotating?
Hi Alice - That's right. Where do you think the ellipticals came from ?

FB

There are a lot of theories, including that they're old spirals! I admit to regrettable ignorance . . .

Dave

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Re: Why record the galaxy rotation?
« Reply #26 on: August 27, 2008, 09:09:45 pm »
Is it possible that angular momentum has been present since the beginning? I was just considering how an object moved through fluid or air creates vortices in its wake, of both CW & ACW. Wouldn't similar actions occur from an event like the 'Big Bang' and although many vortices would be disrupted, a large amount of them would survive and whatever matter was present locally would adopt the spin direction and on collapsing, increase the spin velocity.
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FermatsBrother

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Re: Why record the galaxy rotation?
« Reply #27 on: August 27, 2008, 10:19:56 pm »
So if a cloud started to collapse, it wouldn't necessarily start rotating?
Hi Alice - That's right. Where do you think the ellipticals came from ?

FB

There are a lot of theories, including that they're old spirals! I admit to regrettable ignorance . . .
Hi Alice - We all live in ignorance about the origin of these entities. I certainly am.
My statement above was like prodding the readers of these posts with a pointed stick !! ;D ;D ;D ;D ;D

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« Last Edit: August 27, 2008, 10:25:08 pm by FermatsBrother »
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FermatsBrother

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Re: Why record the galaxy rotation?
« Reply #28 on: August 27, 2008, 10:27:21 pm »
Is it possible that angular momentum has been present since the beginning? I was just considering how an object moved through fluid or air creates vortices in its wake, of both CW & ACW. Wouldn't similar actions occur from an event like the 'Big Bang' and although many vortices would be disrupted, a large amount of them would survive and whatever matter was present locally would adopt the spin direction and on collapsing, increase the spin velocity.
Hi Dave - Sounds good to me !
What's moving thro' ?

FB
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Dave

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Re: Why record the galaxy rotation?
« Reply #29 on: August 27, 2008, 11:30:51 pm »
Hi Dave - Sounds good to me !
What's moving thro' ?

FB
Good point. How about this for a suggestion.
  After inflation high energy particles are winking in & out of existence, but during their brief 'time' their pathways/wakes are interacting within a plasma filled medium creating eddies.(Would this be a suitable enviroment to support vortices ?). The vortex that are able to maintain their state through to the cooling period could then influence the rotation of the 'clumping' heavier particles.
"Personally, I don't think there's intelligent life on other planets. Why should other planets be any different from this one?"                R.A.Monkhouse.