Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Edward Ashmore on 29/09/2011 02:01:02

Title: Where is the centre of the universe?
Post by: Edward Ashmore on 29/09/2011 02:01:02

Edward Ashmore  asked the Naked Scientists:
   
Hi Chris, 

I can kinda get my head around astronomers seeing light that started out 13  billion years ago near the time of the Big Bang. What I'd like to know is, what do astronomers think has happened to those stars whose light set out just after the Big Bang?  And assuming that they would have then been near the centre of the universe what is there now and indeed where is that place now?
 
I'm working my way through the podcasts (http://www.thenakedscientists.com/HTML/podcasts/) and am up to about October 2010 and enjoying them very much. Maybe by the end of 2011 I'll have caught up with the rest of you!

Edd

What do you think?

Title: Where is the centre of the universe?
Post by: Kryptid on 29/09/2011 05:10:56

As we understand it, the Universe either has no "center" or we don't know where such a center is. We are at the center of the visible Universe, but that is relative; if you lived on a planet circling the star Vega you would be at the center of your own visible Universe.

In order for us to know where the "true" center is we would need to be able to observe the entire Universe. Due to the limited speed of light and the Universe's expansion, we will never be able to observe any part of the Universe past a certain distance. In a sense, we are "trapped" inside of the visible Universe (although a few stars and galaxies that we can't see right this moment will eventually be visible to us, we will not be able to see many galaxies and stars as they are receding from us at a relative speed greater than light).

My personal view is that if there is a center, it does not exist in 3-dimensional space.

Title: Where is the centre of the universe?
Post by: imatfaal on 29/09/2011 16:17:58

Hi Edward

SuperC's answer is almost exactly what I would say - and what many others would say too. 

The old analogy of points drawn on a balloon is hackneyed but very good.  Take a semi inflated balloon and get wild with a marker pen, make dots all over it.  Blow up said balloon and watch carefully two dots that you have drawn - they will move apart from each other, no matter which two points you have chosen.  Now, you need to make a dimensional leap - our 3d world is the surface of that balloon (we are a 3d surface in a 4d universe- the balloon is a 2d surface in a 3d universe), and when the universe expands (like the dots on the balloon) we get further away from every point.  Everywhere in the universe (on the surface of the balloon) gets further from everywhere else!  The only place that is neutral and unaffected is the centre of the balloon - but that is not on the surface, ie is not in out reality.

Don't let anyone tell you it is simple or easy - it is not.  the idea of moving beyond our normal comprehension of 3d is counter-intuitive and just downright difficult.

welcome to cosmology and to the forum

Title: Where is the centre of the universe?
Post by: yor_on on 02/10/2011 00:09:32

Another way to think of it. If you ever played those old games pac-man etc, you might remember them moving to the left edge of the screen, to then magically appear at the right side :) If the universe has 'limits' those games might describe the way those 'limits' express themselves inside SpaceTime. And if it is so we will never be able to measure the 'size'. And, if you like, you might consider those 'edges' to be everywhere as you won't be able to say when you passed one as the universe in isotropic on a large scale, looking the same from every point you might measure it from.