Hubble telescope and the size of the universe

[contriver]

Is it believed that the Hubble telescope has given us images of the entire universe? Or is it just that we believe it has given us a glimpse of the very distant universe, yet we have no idea how much farther the universe goes on for beyond what Hubble can see?<br />

 

[primordial]

contriver ! It has been an extreme machine and continues to be, but has limitations. I think its use at this time is shared with the VLT.<br />

 

[robnissen]

Shuttle guy is correct. The problem is that we have no idea what the initial singularity of the big bang was. If was the size of a quark or an atom, the visible universe could be all of the universe. That, however, is extremely unlikely. Conversely, if the initial singuarity was the size of the MW, the visible universe is only a trillionth (* many many trillionths) of the entire universe.

 

[brellis]

hi Rob<br /><font color="yellow">Shuttle guy is correct. The problem is that we have no idea what the initial singularity of the big bang was. If was the size of a quark or an atom, the visible universe could be all of the universe. That, however, is extremely unlikely. Conversely, if the initial singuarity was the size of the MW, the visible universe is only a trillionth (* many many trillionths) of the entire universe.</font><br /><br />There goes my brain again - it gets spread a little thin trying to wrap around this. <img src="/images/icons/crazy.gif" /><br /><br />When Hubble was launched, one of the spokespeople said it could reach the limits of the visible universe. Where I run into trouble is when they say "here's a galaxy 13 Billion ly away, only <i>xxx</i> million years after the big bang."<br /><br />If we know when the big bang occurred, don't we know pretty well how big the universe is? <br /><br />or, the other way around:<br /><br />If we didn't know how big the universe is, how can we say that an object 13 Billion ly away is showing us how things were just after the big bang? <br /><br />btw, I really enjoy being perplexed about stuff like this, especially when I end up getting my brain around it after all! <img src="/images/icons/cool.gif" /> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[qso1]

Nobody I know of believes Hubble has given us the entire Universe unless its someone totally unfamiliar with astronomy.<br /><br />Most folks with even basic knowledge of astronomy and technical developments within, know that Hubble has, as you mentioned...given just a glimpse of the Universe. The current cosmological theories on how far we can see would be tied to how old is the Universe thought to be. The age being based on the expansion of the Universe since the big bang.<br /><br />This is hard to determine based on just observation because no matter where you point a telescope, if there were for example...galaxies or quasars 15 billion light years everywhere you looked, that 15 BYA is based on the optical limitations of the scope. A better scope might stretch the distance to 20 BYA. But in the real Universe, there are not equidistant objects no matter where you look.<br /><br />I fully agree with the second part of your statement. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[brellis]

From Wikipedia<br /><font color="yellow"> The comoving distance from the Earth to the edge of the visible universe (also called cosmic light horizon) is about 46.5 billion light-years in any direction.[4] This defines the comoving radius of the observable universe. The observable universe is thus a sphere with a diameter of 92–94 billion light-years. Since space is roughly flat, this size corresponds to a comoving volume of about<br /><br />frac{4}{3} imes pi imes mathrm{R}^3 = 4.20 imes 10^{32} ext{ ly}^3<br /><br />or 3.56×10^80 cubic meters.<br /><br />The figures quoted above are distances now (in cosmological time), not distances at the time the light was emitted. For example, the cosmic microwave background radiation that we see right now was emitted about 13.7 billion years ago by matter that has, in the intervening time, condensed into galaxies. Those galaxies are now about 46 billion light-years from us, but at the time the light was emitted, that matter was only about 40 million light-years away from the matter that would eventually become the Earth.</font><br /><br />Now I got it all figgered out! <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[qso1]

Yeh, I love it when they say "The comoving distance from the Earth to the edge of the visible universe (also called cosmic light horizon) is about 46.5 billion light-years in any direction." then say "The observable universe is thus a sphere with a diameter of 92–94 billion light-years." Then call it flat. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[brellis]

See, we're at the center of the universe after all! <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[qso1]

Lol, thats what I always thought. I saw some sci fi 50s movie that put it well. The Universe is infinitely large and small which puts us in the middle...or somethin to that effect. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[brellis]

I keep getting tripped up by the timeline that appears in my mind when I look at a Deep Sky image of 13Byo galaxies. I start viewing the universe as a cone - preferably with a scoop of Ben & Jerry's Americone Dream on top! - <img src="/images/icons/wink.gif" /><br /><br />I have trouble discerning between an object 13B ly away that is really old, but on "our side" of the universe, and another object 13B ly away that formed more recently on "the other side" of the universe. Make sense?<br /><br />Do we know the difference in red shift between two such objects? <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[SpeedFreek]

Check out this link - The Distance Scale of the Universe<br /><br />If I understand you correctly, the problem you are having is due to different definitions of distance.<br /><br />An object 13B ly away that is really old would be an object whose light was emitted 13 billion years ago. Using the graph from the link above, it would have a redshift of around z=6 and its apparent angular diameter would indicate it was only around 4 billion light years away when that light was emitted. That object would have a comoving distance of something around 29 billion light years (how far away it is now).<br /><br />Now, an object that formed more recently, but is 13 billion light years away? If that is referring to where it is <i>now</i>, it's comoving distance, then it would have a redshift of z=1.5 or thereabouts. It's light would have been travelling for around 8 billion years and its angular diameter would put it around 5.5 billion light years away when it emitted that light, 8 billion years ago.<br /><br />Is that what you meant? <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[brellis]

Yes! Thanks, speedy! <img src="/images/icons/cool.gif" /><br /><br />I'm enjoying the link very much.<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>