Celestia Forums

Hi I'm new to this forum and I hope I expand my knowledge of our infinite and most amazing universe full of wonder, for us humans are only begining to explore what is space!

To begin I just wanted to ask the most simple of questions: what is your favorite galaxy and why?

thanks and hope to participate further in the infinite future!!!

universe_fascination.

universe_fascination wrote:...of our infinite and.... universe.

Then your first lesson... No, The universe is not infinite.
Infinite time? that is a matter of speculation, depending on which model of the universe's end you wish to believe. As I understand it, a static universe is the most likely scenario in the future, if so, then time may be infinite.

My favourite galaxy is the Milky Way, because even with my feeble observation skills, I can still find it at night.

Hungry4info wrote:Then your first lesson... No, The universe is not infinite.
Infinite time? that is a matter of speculation, depending on which model of the universe's end you wish to believe. As I understand it, a static universe is the most likely scenario in the future, if so, then time may be infinite.

Can you support your claims ?

We currently don't know if the universe is spatially closed or infinite (assuming you're not talking about the Hubble volume, i.e. the observable part of the universe, which is of course finite). According to current data, it may very well be spatially infinite. As for the most likely scenario in the future, it is certainly NOT static ! According to data, space will continue to expand at an even faster rate and comes asymptotatically to a deSitter universe (time will be boundless, in this case).

Actually yes, I was referring to the Hubble volume, it's the first thing that comes to my mind when I hear "universe". But I'll go out on a limb and suggest the entire universe is finite.

My thinking may be crude, so forgive me.

If the big bang created the universe, then we can assume that the universe was not of infinite size at the moment of its creation (for the idea of an infinite sized object expanding is meaningless).

Furthermore, if the universe is infinite, it does not make sense that all the matter will be found in one area, assuming the amount of matter itself is finite. If there is infinite matter in the universe, then it stands to reason (at least in my mind) that there would be an infinitely powerful gravitational force acting on all objects everywhere.

As for the static model of the universe, I got that off of

http://www.physorg.com/news99219988.html

Note my understanding of the universe's future is limited, for I haven't done extensive research into the subject.

Hungry4info wrote:If the big bang created the universe, then we can assume that the universe was not of infinite size at the moment of its creation (for the idea of an infinite sized object expanding is meaningless).

Sorry but this is false. You CAN have an infinite volume AND a Big Bang. There is no contradiction or inconsistency. It's a standard analysis of General Relativity (actually, one of several scenarios from it).

Don't confuse Volume and Density. Big Bang means infinite density (or singularity in density, if you prefer). It says nothing about the volume (or global boundaries). Or in other words : The Big Bang IS NOT an explosion from a single point. There is no central point in the universe (in essence, this is the well known Cosmological principle).

General Relativity is a local theory, and doesn't predict much about the global properties of the universe. The physicists which are applying GR must make some hypothesis on the boundaries, if they want to make some predictions out of GR. This is common to most differential equations to be solved in physics.

It's obvious I know too little about this to sustain myself in a discussion. Is there any accurate sites that describe all this that you could direct me to?

You could go there :

John Baez's Physics FAQ
http://www.math.ucr.edu/home/baez/physics/

I think it's a bit old now, but still pretty good.

In particular, go there :

http://www.math.ucr.edu/home/baez/physi ... entre.html

Alright, thank-you very much.

Wow, I learned some new stuff by reading the posts that were unrelated to my initial question, but that's fine by me!!! Personally my favorite galaxie(s) are The Sombrero galaxy and the Black eye galaxy. The Milky way galaxy will probably become my favorite once I'm on another galaxy and looking in the direction of the Milky way and when I see it I will miss it soo much, it will ultimately become my all time fave. Thanks!!!

I'm gonna go with the milky way. It's where i keep my stuff...