Register | Sign In


Understanding through Discussion


EvC Forum active members: 63 (9161 total)
1 online now:
Newest Member: popoi
Post Volume: Total: 915,585 Year: 2,842/9,624 Month: 687/1,588 Week: 93/229 Day: 4/61 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Question About the Universe
GDR
Member
Posts: 6199
From: Sidney, BC, Canada
Joined: 05-22-2005


(1)
Message 1 of 373 (506827)
04-29-2009 3:46 PM


I'm having a tough time understanding this.
This story just came out recently.
Star 13 Billion Light Years Away
I'm told that the universe is about 13 billion years old, and here we have a star that is observed by us to be 13 billion light years away.
1/ Doesn't this mean that what we are now seeing is that star as it was at a time very shortly after the Big Bang?
2/ I also understood that there is an "event horizon" because of the expansion of the universe that has moved galaxies beyond our ability to perceive them. However here we have a star that has been here since nearly T=0 and we're still able to view it. Why is that?
3/ Using the penny on the balloon analogy shouldn't this mean that we are looking virtually all the way around the balloon, (the universe), and if we looked in another direction that we could see the same star very much closer?
I'm only suggesting this as a topic of discussion for my own information. I don't pretend to have the knowledge to actually debate it.

Replies to this message:
 Message 3 by RDK, posted 04-29-2009 6:39 PM GDR has not replied
 Message 4 by cavediver, posted 04-29-2009 6:45 PM GDR has replied
 Message 6 by Blue Jay, posted 04-29-2009 11:45 PM GDR has replied

  
GDR
Member
Posts: 6199
From: Sidney, BC, Canada
Joined: 05-22-2005


Message 5 of 373 (506851)
04-29-2009 7:37 PM
Reply to: Message 4 by cavediver
04-29-2009 6:45 PM


cavediver writes:
Yes (on the order of several hundred million years after the BB)
Stephen Hawking write that after 1,000 million, (an American billion), years after the BB "Clusters of matter form quasars, stars and proto-galaxies". If as RDK says, the universe is 13.87 billion years old, wouldn't this make it among the very first stars to be formed?
cavediver writes:
We are seeing the "star" before the cosmological expansion carries it over the cosmological horizon. If we continue to observe it over time, we will see it receed and redden to the point that it fades from view.
cavediver writes:
No - even if the Universe is closed as in the balloon analogy, this is on a scale unimaginably larger than the distance to the "star", because of inflation. In an inflated closed universe, the observable universe is a tiny fraction of the whole universe.
As I understand it, we are seeing the light that left that star 13 billion years ago even though, from our perspective, that star has since that time inflated beyond the cosmological horizon. If then, we can look out into space and see things as they were 13 billion ago then what is left to have inflated beyond our ability to perceive?

This message is a reply to:
 Message 4 by cavediver, posted 04-29-2009 6:45 PM cavediver has replied

Replies to this message:
 Message 10 by onifre, posted 04-30-2009 2:11 PM GDR has not replied
 Message 11 by cavediver, posted 04-30-2009 2:19 PM GDR has replied

  
GDR
Member
Posts: 6199
From: Sidney, BC, Canada
Joined: 05-22-2005


Message 7 of 373 (506875)
04-30-2009 12:39 AM
Reply to: Message 6 by Blue Jay
04-29-2009 11:45 PM


Re: Expansion and the Movement of Light
Hi Bluejay
I believe, that although the star would have been closer in the past it doesn't change the fact that the light from that star that was recently viewed left it 13 billion years ago. I would imagine that if we could see that star as things are right now it would likely have burned itself out, but if it still existed it would be much further away than 13 billion light years.

This message is a reply to:
 Message 6 by Blue Jay, posted 04-29-2009 11:45 PM Blue Jay has replied

Replies to this message:
 Message 8 by Blue Jay, posted 04-30-2009 9:16 AM GDR has not replied

  
GDR
Member
Posts: 6199
From: Sidney, BC, Canada
Joined: 05-22-2005


Message 17 of 373 (506984)
04-30-2009 5:48 PM
Reply to: Message 11 by cavediver
04-30-2009 2:19 PM


GDR writes:
If then, we can look out into space and see things as they were 13 billion ago then what is left to have inflated beyond our ability to perceive?
cavediver writes:
I'm not sure I understand your question. Most of the Universe has never been visible to us and never will. This "star" was relatively very close to us for it to be visible at all.
I understand that at as galaxies expand further away from us the rate of expansion increases to the point at which it exceeds the speed of light. At that point in time light is no longer able to reach us, (cosmological horizon) however light that it had previously emitted, (as we perceive it) would continue its journey enroute to our telescope.
My question is this. It seems to me that seeing as how, (as you say, if we have everything right), that what we are seeing is something that is as far back in time as it is possible for us to view. We are viewing it as it was 13 billion years ago. Does this mean then that from our perspective there is no part of the universe that we can't view, even though much of the universe including this particular star has since moved beyond the cosmological horizon.
I hope that makes better sense.
Thanks

This message is a reply to:
 Message 11 by cavediver, posted 04-30-2009 2:19 PM cavediver has not replied

Replies to this message:
 Message 18 by Michamus, posted 05-01-2009 5:29 AM GDR has not replied

  
GDR
Member
Posts: 6199
From: Sidney, BC, Canada
Joined: 05-22-2005


Message 21 of 373 (507338)
05-03-2009 7:11 PM
Reply to: Message 20 by lyx2no
05-02-2009 9:13 AM


Re: Expansion and the Movement of Light
I'd just like to throw this out to anyone. Cavediver writes;
quote:
Most of the Universe has never been visible to us and never will. This "star" was relatively very close to us for it to be visible at all.
This star is 13 billion years old making it one of the byears ago it was still within the cosmological horizon, what would never have been visible to us? Wouldn't anything that had never been visible, or that is not visible to us now, have to be older than this star that is 13 billion light years away, and if this was one of the first stars formed what could be older?
Edited by GDR, : erred in writing million instead of billion as pointed out lvx2no

This message is a reply to:
 Message 20 by lyx2no, posted 05-02-2009 9:13 AM lyx2no has replied

Replies to this message:
 Message 22 by lyx2no, posted 05-04-2009 12:21 AM GDR has replied

  
GDR
Member
Posts: 6199
From: Sidney, BC, Canada
Joined: 05-22-2005


Message 23 of 373 (507349)
05-04-2009 1:07 AM
Reply to: Message 22 by lyx2no
05-04-2009 12:21 AM


Re: Push-of-War
lyx2no writes:
This acceleration has caused the once receding particle horizon to retract. It is speculated that it will reach zero in some 50 billion years.
I can hardly wait.
Thanks a lot lyx2no. That clears it up for me.

This message is a reply to:
 Message 22 by lyx2no, posted 05-04-2009 12:21 AM lyx2no has not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024