Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jopie64 on 12/02/2013 21:22:32

Title: Age and size of the universe
Post by: jopie64 on 12/02/2013 21:22:32

I recently read a new universe distance record was measured. An object was detected at about 12 bilion lightyears away. They also say that the universe is about 13.7 bilion years old. But how is that possible? Because the conclusion that can be drawn from the measurement is, I think, that the universe was at least 12 bilion lightyears big 12 bilion years ago already!

Title: Re: Age and size of the universe
Post by: imatfaal on 14/02/2013 10:53:34

Several factors
Universal Expansion - at present clusters and super-clusters (ie groups of galaxies) are being measured as all moving apart.  The rate at which the distance between them is increasing is faster than the speed of light!  I know this might go against lots you have heard about speed of light being sacrosanct - but in this case it is not that clusters are travelling through space at this speed, it is that the gaps between them are increasing.  Sounds a bit mad but there is a "metric expansion" of space.  Things that are held together (like you) by electromagnetic attraction do not get effected because the forces that hold your body together are far far stronger than the background expansion.  Even astromnomical stuff held together by gravity is stronger than the expansion - in fact small groups of galaxies remain gravitationally bound (like us, Andromeda, and the others of the local group).  A metric expansion like this one works in a way that the further something is away the faster it is seen to be receding  - so distant galaxies can be really shifting :-)

2.  Inflation.  The first few moments of the big bang are very complicated and we still can only speculate.  One hypothesis that helps explain a lot is inflation.   Inflationary theories suggest that between 10^-36 of a second to 10^-32 of a second  (that's an astonishingly short time period - far shorter than we can detect with the best atomic clocks) that the universe inflated by a huge amount - it got 10^78 times bigger by volume.

This two factors (along with a few others) mean that although the universe is 13.6ish billion years old - there are galaxies that are 46 billion light years away from us!  I don't remember seeing a distance record being announced but I do seem to recall an announcement that a galaxy which they believe was formed about 12 billion years ago (ie soon after the formation of the universe) had been detected. This was the furthest galaxy in time and therefore probably also in distance - it would have been a  deal further than 12 billion light years away.

Title: Re: Age and size of the universe
Post by: jopie64 on 14/02/2013 14:52:03

Thanks! This explains alot.

And indeed, I think I mixed up 12 billion years and 12 billion lightyears.