Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: randalf on 26/02/2009 10:30:03

Title: Does everything in the Universe revolve around a common centre?
Post by: randalf on 26/02/2009 10:30:03

Randal F  asked the Naked Scientists:
   
Ni Hao from China,

As you are doing your astronomy shows (http://www.thenakedscientists.com/HTML/podcasts/naked-scientists/show/2009.02.22/), I am wondering....we (the Earth and other planets) revolve around the sun, our solar system revolves inside the Milky Way, and the Milky Way revolves around something else (??) as do all of the other galaxies.

What I want to know is what/where do they all revolve around? The centre of the universe??? And if the universe is expanding, where is it expanding from? Again, the centre of the universe???

I won't even try to understand what it is expanding into at this stage. The concept of nothing is too much for my little brain.

Thank you

Randal

What do you think?

Title: Does everything in the Universe revolve around a common centre?
Post by: yor_on on 26/02/2009 12:27:22

This is from 'MaddCow' but it still makes some sense to me:)

"
The best explanation is that galaxies formed from a spinning cloud (well, actually, probably many spinning clouds, but all with about the same spin). As the cloud contracted, it started spin faster, due to the law of conservation of angular momentum.

This spin flattened out the shape of the galaxy due to centripedal force. The same thing happens to stars. As they contract, their spin increases, and gas and dust from their formation makes a disk around the star. From this disk, planets are formed. That is why the solar system displays this feature as well.

Now elliptical galaxies are a different story. They are formed from galactic collisions. When two disk galaxies collide and merge, their star's orbits are mixed up and scrambled, thus resulting in a disorderly, spherical shape.

A very extreme case of spin-up through contraction is the neutron star, which may spin as fast as 1000 times a second! "

But those galaxies rotation do not fit the mass calculated by the stars involved?
http://en.wikipedia.org/wiki/Galaxy_rotation_problem

------
As for a defined Center of the universe?
It's like the holy grail I think :)

Title: Does everything in the Universe revolve around a common centre?
Post by: Vern on 26/02/2009 20:05:20

Quote from: randalf

What I want to know is what/where do they all revolve around? The centre of the universe??? And if the universe is expanding, where is it expanding from? Again, the centre of the universe???

No one knows where, or even in what direction, is the centre of the universe. The Cosmic Microwave Background Radiation is a candidate for the average inertial frame of the universe.

There was a paper that circulated a while back that suggested that the Milky Way galaxy was at the centre of a huge bubble-like void. It used this concept to explain why the universe seems to be expanding. That paper was followed quickly by several papers showing that it was an unlikely scenario. [:)] But creationists still hang on to the earlier paper.

Title: Does everything in the Universe revolve around a common centre?
Post by: lyner on 26/02/2009 20:59:32

I don't think there is evidence of any net angular momentum in the Universe. There are regions in which there is a net value of so much about a particular, all solar systems and spiral galaxies, for instance and there are other regions which will cancel this out as a whole.

Title: Does everything in the Universe revolve around a common centre?
Post by: Damo the Optics Monkey on 27/02/2009 00:54:17

Here (http://math.ucr.edu/home/baez/physics/Relativity/GR/centre.html) is a bit of an informative article about this question.

Title: Does everything in the Universe revolve around a common centre?
Post by: tsr on 20/03/2009 06:26:30

Thanks, Damo!
I was just about to ask something similar to Nao's question, but luckily I found this thread via the search function of the forum. When I googled for the question whether the universe has a centre or not, I only found articles explaining why the expansion of the universe does not enable us to conclude where a possible centre might be. Sadly, that doesn't tell us anything about whether there is a centre or not. It only tells us that the expansion has nothing to do with it. That's great to know, but one could also argue that ducks don't have anything to do with it, either (which I suspect they don't, but you never know).
So finally your link to the FAQ gave me a satisfactory answer, which is that we just don't know. Thanks again!

Title: Does everything in the Universe revolve around a common centre?
Post by: Raghavendra on 20/03/2009 06:42:17

Hmmm nice question....

      See there are more than million galaxies and they are moving a speed... we can't definitly say that galaxies are revolving around!!!
 
             To discover the centre os galaxy.. Our telescope must be too much advanced .. we can't accept theory!!!   we also need prove..


    Untill then we have to wait !!!!                 

Title: Does everything in the Universe revolve around a common centre?
Post by: Chemistry4me on 20/03/2009 08:40:10

That's a funny e-mail address you've got there tsr. [:)]

Title: Does everything in the Universe revolve around a common centre?
Post by: syhprum on 20/03/2009 17:42:08

The universe by definition is all there is and has no centre and nothing to revolve relative to

Title: Does everything in the Universe revolve around a common centre?
Post by: yor_on on 29/03/2009 02:45:27

There seem to be different ideas about that.
One is that we first had a 'space', into that space particles, inflated at a very fast pace and then created gases, and matter. The 'inflation' was faster than light in a vacuum under those first moments. if this is true it make me wonder how 'space' can exist on its own? Also if it had a 'time' and if that 'time' also had an arrow before 'matter' became. It must have, it seems to me.

for myself I see it as some sort of 'point' inflating creating space as matter is created. And only 'space' existing is to me a extremly strange idea :) And as spacetime is a 'whole' concept to me that inflation creating 'distances', as it created space and matter, explains how it could 'inflate'. What we call distance is a concept relating to spacetime, and as this inflation took place before spacetime, the idea of 'distance' had no relevance to it. Looking at it this way you don't need to define it as inflating 'faster than light' as that too is a definition of the barriers containing spacetime. If 'distance' is a relation of spacetime, as well as 'c', and all those other interlocked properties we see regulating where we live then we don't need those to explain inflation. Looking on it this way one still need something explaining those 'transitions' from quarks gluons to particles, gases, and finally to 'matter'. But :) I don't have to apply spacetimes 'rules' for the inflation.

Title: Does everything in the Universe revolve around a common centre?
Post by: DoctorBeaver on 29/03/2009 10:23:13

Quote from: tsr on 20/03/2009 06:26:30

I was just about to ask something similar to Nao's question,

Ni hao isn't a name. It's Mandarin for "Hello"  [:D]

Title: Does everything in the Universe revolve around a common centre?
Post by: Chemistry4me on 29/03/2009 10:29:09

Hee hee, yes indeed. [:D]

Title: Does everything in the Universe revolve around a common centre?
Post by: Raghavendra on 29/03/2009 10:55:05

I too know to laugh .. hahaha ha ha aha [;D]

Title: Does everything in the Universe revolve around a common centre?
Post by: Chemistry4me on 29/03/2009 11:00:53

Since when did you starting learning Chinese then? [:)]

Title: Does everything in the Universe revolve around a common centre?
Post by: tsr on 30/03/2009 20:54:01

Quote from: DoctorBeaver on 29/03/2009 10:23:13

Ni hao isn't a name. It's Mandarin for "Hello"  [:D]

Ugh! I'm sorry, of course I meant the initial poster. And I still think the FAQ is good. :)