Notices
Results 1 to 12 of 12

Thread: The Oldest Galaxy

  1. #1 The Oldest Galaxy 
    Forum Senior Booms's Avatar
    Join Date
    Sep 2008
    Location
    The perceptual schematic known as earth
    Posts
    361
    Is a quasar thingy someone discovered.
    It emited the light we saw 13.7 billion years ago (ish) meaning it emitted that light 770 million years after the big bang.


    However, since we are seeing this 13.7 Billion years later. Does this mean that 770 million years into existence that the universe had already expanded 13.7 billion lightyears? Or was it closer, but expansion has made the gap bigger before the light could reach us?
    Sorry, I'm not really sure what I'm asking myself. But every impulse in my body is screaming "this is wrong!" becuase I just can't understand how light can take 13.7 billion years to cross 770 million years distance


    It's not how many questions you ask, but the answers you get - Booms

    This is the Acadamy of Science! we don't need to 'prove' anything!
    Reply With Quote  
     

  2.  
     

  3. #2  
    Moderator Moderator Dishmaster's Avatar
    Join Date
    Apr 2008
    Location
    Heidelberg, Germany
    Posts
    1,624
    Quote Originally Posted by Booms View Post
    Is a quasar thingy someone discovered.
    It emited the light we saw 13.7 billion years ago (ish) meaning it emitted that light 770 million years after the big bang.


    However, since we are seeing this 13.7 Billion years later. Does this mean that 770 million years into existence that the universe had already expanded 13.7 billion lightyears? Or was it closer, but expansion has made the gap bigger before the light could reach us?
    Sorry, I'm not really sure what I'm asking myself. But every impulse in my body is screaming "this is wrong!" becuase I just can't understand how light can take 13.7 billion years to cross 770 million years distance
    Hmm, and I am not eactly sure what you are asking. First of all, you should realise that the distance to the CBMR curtain is not necessarily (most probably) not the size of the universe. We just can't look farther away. This also means that 770 million years after the Big Bang the universe did not neccessarily have a diameter of 770 million lightyears. So, it is no big wonder that the light did not only take 770 million years (or less) to reach us. But you are forgetting the expansion that constantly increased (and still does) the distances - even more so for two positions that were widely separated. Maybe you could use the balloon analogon again. Imagine that there are two points seprated by a certain distance. Also imagine that the balloon constantly expands and so increases the distance between the two points. Try now to draw a line between the two points. The length of that line is then determined by the distance between those points when the line reaches the second point, not when you started to draw the line. In turn, the distance at an early epoch of the universe does not matter; only the distance at is now.

    I am not sure, if this is really an answer.


    Reply With Quote  
     

  4. #3  
    Forum Professor
    Join Date
    Oct 2006
    Posts
    1,595
     
    A light echo is a phenomenon observed in astronomy. Analogous to an echo of sound, a light echo is produced when a sudden flash or burst of light, such as that observed in novae, is reflected off a source and arrives at the viewer some time after the initial flash. Because of their geometries, light echoes can produce the illusion of superluminal speeds.[1]

    http://en.wikipedia.org/wiki/Light_echo

    By change are you thinking the above or the reverse of your thoughts?

     
    But every impulse in my body is screaming "this is wrong!" because I just can't understand how light can take 13.7 billion years to cross 770 million years distance.
    It can't...and even if it could, how could it ever be proved.
    Reply With Quote  
     

  5. #4  
    Quagma SpeedFreek's Avatar
    Join Date
    Jan 2011
    Location
    London, UK
    Posts
    2,787
    The light was emitted when the universe was a lot smaller, but was expanding very fast. The expansion was so fast that it was increasing the distance in between that light and its eventual target (here!), faster than the speed of light!

    As the light moved towards us from the point of view of that oldest quasar, the quasar and the light were being taken away from us by the expansion of the universe. By the time the rate of expansion had slowed enough for that light to start coming back towards us (from our point of view), the universe was over 4 billion years old, and that light was passing galaxies that were over 5 billion light-years away at that time!

    Eventually that light reached us here, over 13 billion years after it was emitted. The quasar was less than 3 billion light-years away when the light was emitted, and is now over 30 billion light-years away as its light finally reaches us.

    Here is a link to a couple of posts I made a while back, with a diagram and an explanation of how all this works!

    Expansion of the Universe.
    Last edited by SpeedFreek; July 26th, 2011 at 05:03 PM. Reason: added link
    Reply With Quote  
     

  6. #5  
    Quagma SpeedFreek's Avatar
    Join Date
    Jan 2011
    Location
    London, UK
    Posts
    2,787
    Oh, and the 770 million years figure was simply the age of the universe, and does not reflect the distance to that quasar at that time. The edge of the observable universe has always been receding faster than light.
    Reply With Quote  
     

  7. #6  
    Suspended
    Join Date
    May 2008
    Posts
    1,096
    Booms. The big point about this quasar is that it exists.

    Originally massive black holes were thought to have formed some two to four billions years after the big bang but this was later revised to 1.2 billions years after the big bang.


    When the black hole was born: Astronomers identify the epoch of the first fast growth of black holes


    Now we have a two billion solar mass black hole formed just 770 million years after the big bang, with no idea of how it happened.
    Reply With Quote  
     

  8. #7  
    Suspended
    Join Date
    May 2008
    Posts
    1,096
    Quote Originally Posted by SpeedFreek View Post
    The edge of the observable universe has always been receding faster than light.
    Then you can never have actual proof that it is happening.
    Reply With Quote  
     

  9. #8  
    Quagma SpeedFreek's Avatar
    Join Date
    Jan 2011
    Location
    London, UK
    Posts
    2,787
    Considering the nature of cosmology, what would you define as "actual proof" ?
    Reply With Quote  
     

  10. #9  
    Suspended
    Join Date
    May 2008
    Posts
    1,096
    We cannot have actual proof of most of it.

    Galaxies move over such time periods that we cannot observe it happening so must assume they are moving away from each other, based on the whistle of a train travelling past us.

    96% of the universe cannot be seen or detected, so it is said.

    We find contrary evidence like the two billion solar mass black hole existing 770 million years after the BB (mentioned elsewhere), the BB failing the afterglow test, the fact that time dilation in supernovae is not found over 6 billion light years away, the Dark Flow, etc and they are just pooh-poohed and anyone who dares mention them is called a crank who does not know cosmology.

    The basis of science I was told at school is that through tests you dismiss everything that is not possible leaving you with the possible (which assumes that there are no unknowns which may affect the answer you get). But cosmology is made up of theories which start: "What if.....?"

    I think we need to keep an open mind to alternatives in this particular field rather than setting things in stone because we cannot have the same kind of proofs we can get in most other fields of science.
    Reply With Quote  
     

  11. #10  
    Quagma SpeedFreek's Avatar
    Join Date
    Jan 2011
    Location
    London, UK
    Posts
    2,787
    Our models of large structure formation and evolution in a BB universe are not good enough yet state that you cannot have a 2 billion solar mass black hole at t=770 Myr. Our previous assumptions about galaxy evolution might need re-evaluating, but that does not change all the observations that point to them evolving in an expanding universe.

    You will need to explain the "afterglow test" you refer to.

    Are you confusing quasars with SNIa supernovae? We have good evidence for time-dilation of SNIa out to a redshift of z=1.7 so far - a look-back time of nearly 10 billion years.

    Quasars cannot be used as a test for time-dilation, as the events that cause them are not of such regular periods as the light curves as SNIa. Quasars are not good standard candles in that sense.
    Reply With Quote  
     

  12. #11  
    Suspended
    Join Date
    May 2008
    Posts
    1,096
    Big Bang's afterglow fails shadow test:


    Big Bang's Afterglow Fails Intergalactic 'Shadow' Test


    Discovery that quasars don't show time dilation mystifies astronomers:


    Discovery that quasars don't show time dilation mystifies astronomers


    Even standard candles may not be standard candles. A Type 1A supernova found a while back was twice as bright as expected (so making it look much closer than it actually was). The explanation was simply that it was spinning faster than many others, so could hold more mass before collapsing.


    New Kind of Supernova Discovered


    The biggest void discovered so far in our "smooth" universe is 3.5 billion light years across:


    The Eridanus Void: Does a MegaMassive Black Hole One-Billion Light Years Across Exist? (A 'Galaxy' Most Popular)


    And since it is claimed that we cannot see most of the universe, far bigger ones may exist. Imagine how bad it would have been without inflation?


    Like GRB's, all quasars are said to be very far away but if they were confusing part of their redshift due to the SMBH both possesses, both could be much nearer, so far less violent than thought. Several years back an astronomer thought he had found something moving away from us faster than light but he had not allowed for the redshift caused by the object's black hole, so got a redshift reading too high.
    Reply With Quote  
     

  13. #12  
    Quagma SpeedFreek's Avatar
    Join Date
    Jan 2011
    Location
    London, UK
    Posts
    2,787
    Some valid questions indeed.


    Quote Originally Posted by Cyberia View Post
    Big Bang's afterglow fails shadow test:

    Big Bang's Afterglow Fails Intergalactic 'Shadow' Test
    This was largely solved when the WMAP 3 year results were more thoroughly analysed. The analysis even began before that article was published!

    [astro-ph/0608503] Intracluster Medium through three years of WMAP

    And we await the results from Planck to investigate further.

    Quote Originally Posted by Cyberia View Post
    Discovery that quasars don't show time dilation mystifies astronomers:

    Discovery that quasars don't show time dilation mystifies astronomers
    As I was alluding to earlier, there is a debate as to whether quasars should show time-dilation in line with SNIa, in that we have a poor understanding of quasar evolutionary models. It is considered more likely that our understanding of quasars is wrong, than it is that they prove the universe is not expanding.


    Quote Originally Posted by Cyberia View Post
    Even standard candles may not be standard candles. A Type 1A supernova found a while back was twice as bright as expected (so making it look much closer than it actually was). The explanation was simply that it was spinning faster than many others, so could hold more mass before collapsing.

    New Kind of Supernova Discovered
    You will notice that, from the commentary provided at that link, this does not bring into question whether the universe is expanding or not, it just makes it more complex to measure that expansion.

    Quote Originally Posted by Cyberia View Post
    The biggest void discovered so far in our "smooth" universe is 3.5 billion light years across:

    The Eridanus Void: Does a MegaMassive Black Hole One-Billion Light Years Across Exist? (A 'Galaxy' Most Popular)
    Yup. And there are many possible explanations for this and none that I know of preclude the universe from expanding. Some suggest it could even be evidence of our expanding "bubble universe" touching another, early on.

    All relevant questions to the subject of cosmology, and in need of further investigation.

    On a more personal note, I feel it is especially important at this time that I point out the following - I only think the universe is expanding because I have examined, over the past decade or so, as much of the evidence for it as possible, and so far that evidence far outweighs the evidence against it. If there comes a time when the evidence against it outweighs the evidence for it, there will be a change in paradigm that I will happily accept.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •