Expanding Universe

Got a beginners' question? No matter how elementary, our friendly forum community and magazine writers will answer it.

Expanding Universe

Postby techno » Mon Aug 23, 2010 6:33 pm

Ok here is my question(s):-
We observe that the universe is expanding by checking the red shift on the most distant object we can find. These objects are million/billions of light years away and therefor million/billions of years old, so the redshift that we are looking at is extreamly old. How do we know that the object (or the objects that have since been made of it's embers) are still moving at that same approximate velocity and direction NOW?
I guess the actual question is, how can we say the universe is still expanding when our observed data is more that a little out of date...

OK second question:-
Assuming the universe expands until it runs out of energy (which I understand is what will happen if it continues to expand) and also assuming that there have been other universes before (yeah I know... but assuming) Could the expanding shell of a long dead universe (and any others before it...) be the cause of what we call Dark Energy today....?

Ok I'm done...


for now [;)]
techno
 
Posts: 8
Joined: Mon Feb 13, 2012 7:07 pm

RE: Expanding Universe

Postby uea74 » Mon Aug 23, 2010 7:56 pm

The data is billions of years old, but, and it's a big but, the best model to best fit the data we have would indicate that the universe is expanding, and that the expansion is accelerating.

However what was assumed to be correct 5-10 years ago is now believed to be incorrect and what comes out in the next 10 years may cause it to change again.

Second point. Don't have a problem with the line of thought, however would have guessed that if matter from the previous big bang had degenerated over what would be a VERY long time that it would be the Dark Matter component more then the Dark Energy component.

Perhaps the "matter" that we are from can have no real interaction with this previous matter/energy so the lack of interaction (gravity excluded) causes us to refer to it as Dark.

Unfortunately we get to the realm of science fiction. Then again I suppose that when it comes to Dark Matter/Energy it is a lot of supposition and guesswork - hence fiction not fact.
uea74
 
Posts: 459
Joined: Mon Feb 13, 2012 6:54 pm

RE: Expanding Universe

Postby nighthawk » Tue Aug 24, 2010 12:40 am

I know this isn't exactly answering your question but just to clarify something.
'Velocity' doesn't mean speed. It is actually a combination of speed AND direction.
Thus we have 'Recessional' velocities or 'radial' velocities etc.
nighthawk
 
Posts: 54
Joined: Mon Feb 13, 2012 7:05 pm

RE: Expanding Universe

Postby techno » Tue Aug 24, 2010 11:46 am

[quote]ORIGINAL: nighthawk

'Velocity' doesn't mean speed. It is actually a combination of speed AND direction.
[/quote]

Cool, learn something new every day [:)]
I knew they should have let me do Physics at school!!
techno
 
Posts: 8
Joined: Mon Feb 13, 2012 7:07 pm

RE: Expanding Universe

Postby nighthawk » Tue Aug 24, 2010 9:46 pm


[quote]ORIGINAL: Techno

[quote]ORIGINAL: nighthawk

'Velocity' doesn't mean speed. It is actually a combination of speed AND direction.
[/quote]

Cool, learn something new every day [:)]
[color=#CCFF33]I knew they should have let me do Physics at school!![/color]

[/quote]
You still can. There is the Open University which is excellent. Even better if you can get an employer or someone to pay for it.
I only did the Science Foundation course and never got round to the Astronomy course which I intended to follow up wit. (Due to unforseen circumstances) but they teach you well. Some of it actually stuck with me lol.
nighthawk
 
Posts: 54
Joined: Mon Feb 13, 2012 7:05 pm

RE: Expanding Universe

Postby charmquark » Wed Aug 25, 2010 2:30 am

I am in the middle of teaching myself physics as i didn't do very well in school........I have been studying for 8 and half months now.......just wish i had the grades to be able to do it for real.......or the money to do proper home studying [:)] anyways i am loving this thread.....I heard that the universe will expand forever i am not sure about this kinda way outta my league, I have also heard that it will come to a bad end in a big crunch.....all amazing stuff in my eyes [:D]
charmquark
 
Posts: 199
Joined: Mon Feb 13, 2012 7:06 pm

RE: Expanding Universe

Postby spartacus » Wed Aug 25, 2010 1:03 pm

Just a thought with the Multiverse in mind, could the accelerating expansion of the Universe be influenced by the accelerating contraction (big crunch) of a bordering universe or multiples thereof ?
This would put dark energy to bed ?
Feasible or the ramblings of a damaged mind ?
Over to our cosmologists [:D]

le Keef
spartacus
 
Posts: 2217
Joined: Mon Feb 13, 2012 6:30 pm

RE: Expanding Universe

Postby techno » Wed Aug 25, 2010 2:26 pm

[quote]ORIGINAL: nighthawk
You still can. There is the Open University which is excellent. Even better if you can get an employer or someone to pay for it.
I only did the Science Foundation course and never got round to the Astronomy course which I intended to follow up wit. (Due to unforseen circumstances) but they teach you well. Some of it actually stuck with me lol.
[/quote]

Yeah I have been looking at OU courses. Did you find it OK? Wish I could get work to pay for it...

[quote]ORIGINAL: Spartacus
Just a thought with the Multiverse in mind, could the accelerating expansion of the Universe be influenced by the accelerating contraction (big crunch) of a bordering universe or multiples thereof ?
[/quote]

You think universes are like bubbles, when one shrinks the others around it get bigger?
My thought was the universes could start from the same point, so the long dead shells of previous universes acted (via gravity...?) to pull our universe out. Of course this would not explain why the very first universe continued to expand... [:D]
On that point do we think there is any "matter" left in the core area of our universe, or is our universe just a shell?

[quote]ORIGINAL: uea74
Second point. Don't have a problem with the line of thought, however would have guessed that if matter from the previous big bang had degenerated over what would be a VERY long time that it would be the Dark Matter component more then the Dark Energy component.
[/quote]

When it comes to time on a universal scale, does time actually matter? Let’s face it, only life really cares what time it is. [:D]
I guess it all depend on what the matter from the previous universe degenerated into... I guess Dark energy could be attraction of the other universes on ours and Dark Matter could be the degenerated matter that’s still hanging around in ours.
techno
 
Posts: 8
Joined: Mon Feb 13, 2012 7:07 pm

RE: Expanding Universe

Postby rzero » Wed Aug 25, 2010 3:16 pm

This might help regarding Redshift

http://www.star.le.ac.uk/~pae9/twitter/distance.html
rzero
 
Posts: 840
Joined: Mon Feb 13, 2012 6:42 pm

RE: Expanding Universe

Postby spartacus » Wed Aug 25, 2010 7:26 pm


[quote]ORIGINAL: Spartacus
Just a thought with the Multiverse in mind, could the accelerating expansion of the Universe be influenced by the accelerating contraction (big crunch) of a bordering universe or multiples thereof ?
[/quote]

[quote]ORIGINAL: Techno
You think universes are like bubbles, when one shrinks the others around it get bigger?
My thought was the universes could start from the same point, so the long dead shells of previous universes acted (via gravity...?) to pull our universe out. Of course this would not explain why the very first universe continued to expand... [:D]
On that point do we think there is any "matter" left in the core area of our universe, or is our universe just a shell?
[/quote]

That's exaclty what I'm talking about ! [:D]

It's a shame interesting stuff like this gets overlooked when there's another (ZZZZzzzzzzzz here we go again) AGW topic raging in "Non Astro Chat" [;)]

Keef


spartacus
 
Posts: 2217
Joined: Mon Feb 13, 2012 6:30 pm

Next

Return to Ask a silly (astronomy) question

Who is online

Users browsing this forum: No registered users and 0 guests