Is the red shift discrepancy the same at all distances?

[ianke]

I'm sorry but I edited my last post and maby you didn't read it.<br />look up one.<br /> <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

If you read through the article I posted earlier in this thread about the <b> metric </b> expansion of space, wou will see that it is the metric of space that is expanding, whereby spacetime itself is described by a metric which changes over time in such a way that the spatial dimensions appear to grow or stretch as the universe gets older.<br /><br /><font color="orange"> "The expansion of space is </font><b>conceptually different </b> <font color="orange"> from other kinds of expansions and explosions that are seen in nature. Our understanding of the "fabric of the universe" (spacetime) requires that what we see normally as "space", "time", and "distance" are not absolutes, but are determined by a metric that can change. In the metric expansion of space, rather than objects in a fixed "space" moving apart into "emptiness", it is the space that contains the objects which is itself changing. It is as if without objects themselves moving, space is somehow "growing" in between them." </font><br /><br />The way I understand it, if the metric expansion doubles over, say 1 billion years, then every unit doubles over that time. 1 meter becomes 2 meters, universe size =1 becomes universe size = 2. If the expansion carries on at the same rate, it can be considered <i> constant. </i> It is the <i> rate of metric expansion </i> that is staying constant. The rate is constant, the metric is increasing.<br /><br />So everywhere in space could at any given (universal) time, expand at the same rate. In your local area, everything is normal and space seems to expand very slowly. But the further away things are <i> at that time, </i> the faster they are receding from you. They might even exceed the speed of light out past a certain distance. But out at that distance itself, everything is normal with very slow expansion.<br /><br />And all this is <i> before </i> we consider the time it takes for the light from these events to reach us, and how it skews our view of the <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[ianke]

cotrol_group<br />you wrote:<br />"Under this model, we should expect to see more distant objects receding faster than closer objects - which, if my understanding is correct, is exactly what we do observe; so it seems a linear model of expansion is supported. "<br /><br />This is exactly my point as well, but the red shift appears to say that it is even faster than expected. It appears the light has shifted even further than can be accounted for by just the expansion theory alone. (At least that is what I understand is being said) <br /><br />Now one of two things (or maby a combination of both) has occured. Remember that we are only looking at one single data point for any given object.<br /><br />1.The red shift has been effected by other forces. (like Wolfe's effect or gravitational distortions or possibly other things that I don't know about) This would render the data as questionable at best<br /><br />2. The universal expansion is now or has been at some earlier time at a faster rate.<br /><br />2a. The most common explaination is that it is getting faster (time one 1light year becomes 2light year. />> move forward to time two>> 1 light year becomes some distance greater than 2light years) This is the point at which the "dark energy" becomes needed to drive the acceleration.<br /><br />2b. The universe was moving a lot faster in the past than it is now. This would still account for a greater expansion observed by looking at that point of data. This slowing of expansion could be accounted for by a universe with enough mass to eventually draw itself back to a big crunch. Thus even though it is still expanding it could be slowing down to the speed we see it today. <br /><br />2c. I guess it could just be moving faster throughout time but our observations would possibly detect that from nearer objects which they do not at this time. <br /><br /><br />Anyway, whatever causes the discrepancy in the redshift observations is still up in the air as far as I can see. sin <div class="Discussion_UserSignature"> </div>

 

[control_group]

Ah, I am experiencing a glimmer of understanding!<br /><br />Ianke - yes, I was writing my reply when you edited your post; I now understand what you're saying. Which is also what speedfreek is saying, if I'm reading correctly.<br /><br />Check me, either of you, if I'm suddenly way off base.<br /><br />Over time, space itself is expanding - something like a stretching rubber sheet, to borrow an overused analogy - at some rate. That rate is defined by the increase between any two points, so is exponential in the conventional sense of measuring distances. It's linear, however, in terms of how much "stretching" is going on per unit time. The rate of this expansion is such that it's only apparent at very large distances. Moreover, no matter how long you were to observe, you would never notice a local change, since the instruments and phenomena you're using to measure the change would also be expanding - so, even a billion years from now, a meter will still be one 299,792,458th of a light second.<br /><br />My question then is: say you were to launch an instrument out towards the farthest known object and, through liberal application of hand-wavium, you accelerated it to .9c. It also magically taps into vacuum energy to blast detectable (and massively redshifted) signals back towards us out to arbitrary distances. In a billion years, you would expect to see it 9E8ly away, at 2 billion years, 1.8E9ly away, and so forth. At some point, would you eventually be able to detect this effect, and perceive that it was further away than it "should" be?

 

[ianke]

It looks as if we are addressing 2 different issues here. the metric and the red shift data. It is kinda fun to switch gears though. <img src="/images/icons/smile.gif" /><br /><br />Note: I see why others come to you for these issues though. speedfreek you rock at this. I hope you instruct somewhere, otherwise you have missed your calling<img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[control_group]

Ianke, I'm about to be officially out of my depth, since I don't know exactly what feature of the CMB can be plugged into which math to make the statement, but I was under the impression that the Boomerang experiment in 2000 had essentially confirmed that the universe is flat, and won't recollapse.<br /><br />This would be a data point separate from galactic redshift that indicates this - but again, I'm not knowledgeable enough to weigh in on exactly what data were intepreted and how to reach this conclusion. <br /><br />Also: ditto Ianke's post, speedfreek, you've helped my understanding a lot. <br /><br />And much the same to you, Ianke, this conversation has been very illuminating for me.

 

[ianke]

Control_Group<br /><br />1. the speed of light will remain the speed of light it is a constant.<br /><br />2. the red shift is measured only in comparison to cosmic events that are known/believed to have a constant spectra (cefeid variables(sp?) for closer objects and type 1a supernovae for far distances)<br />It is the observation of the shift towards the red for the signature spectra of that known object that give rise to speed and distance measurements <br /><br />Reguarding:<br />"My question then is: say you were to launch an instrument out towards the farthest known object and, through liberal application of hand-wavium, you accelerated it to .9c. It also magically taps into vacuum energy to blast detectable (and massively redshifted) signals back towards us out to arbitrary distances. In a billion years, you would expect to see it 9E8ly away, at 2 billion years, 1.8E9ly away, and so forth. At some point, would you eventually be able to detect this effect, and perceive that it was further away than it "should" be? " <br />I don't know,but I'll think about it<img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[ianke]

Good Point!<br /><br />reguarding this:<br />"Ianke, I'm about to be officially out of my depth, since I don't know exactly what feature of the CMB can be plugged into which math to make the statement, but I was under the impression that the Boomerang experiment in 2000 had essentially confirmed that the universe is flat, and won't recollapse." <br /><br />This may kill my entire argument again, but let me think on it a while. <img src="/images/icons/crazy.gif" /> <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

<font color="yellow"> I'm picturing an explosion where some number of objects start out adjacent and then are thrust apart from each other by a single impulse. I'll use meters and seconds as units, just for convenience. So let's say that the initial velocity is 1m/s. After one second, two objects (objects A and B) on opposite sides of the starting point will be 2m apart, after 2 seconds, 4m, after 3 seconds, 6m, etc. That's (obviously) a linear rate of expansion. Every second, the sphere defined by the objects increases in diameter by 2m. </font><br /><br />Try not to picture an explosion. The expansion of space is not the same as an explosion. Your example is using inertial movement to achieve velocity. The inertial movement of objects in space is separate from the expansion of space. On the local scale, planets move around stars which move within galaxies due to inertia (and maybe dark matter works on the galactic scale, inertially). Galaxies can also be gravitationally attracted to each other (more inertial movement).<br /><br />But the expansion of space is not inertial. The expansion of space drags along all the matter within, whilst the matter interacts inertially.<br /><br />You are using simple trigonometry based upon a centre of expansion in your linear example. With the metric expansion of space there is no single centre of expansion, no single point where the expansion began. All points in space are expanding at the same rate, pushing every point away from every other point.<br /><br /><font color="yellow"> Under this model, we should expect to see more distant objects receding faster than closer objects - which, if my understanding is correct, is exactly what we do observe; so it seems a linear model of expansion is supported. </font><br /><br />No that is not what we think we are observing. Your linear model is based on objects moving through inertia only. They may well be moving through inertia, but space is expanding too. These objects wer <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[dragon04]

A linear rate would not accurately describe either the increasing volume of a given space in more than two physical dimensions or the rate at which it expands relative to a discrete point.<br /><br />That expansion would always be exponential, right?<br /><br /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[acsindg]

Absolutely Dragon04<br />If the edge of space moves 1 unit outwards then the volume of space enclosed will increase by 4/3 pi R />3. But whether it expands at 36 or 72 km/sec is to miss the point. What is causing the universe to expand? Probably Dark Energy! But what is causing the dark energy? Probably electric repulsion?? Look up alternative electric magnoflux universe for another view. Clive <br />

 

[brellis]

The catch for me is that the rules of cosmology now presume there's something <i>beyond</i> the measurable universe!<br /><br />A Beautiful Galactic Group Picture <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>

 

[why06]

<font color="yellow">What the Hell are you guys talking about. <img src="/images/icons/wink.gif" /><font color="white"><br /><br />Theres no way in hell 2x or 4x or 1000000x is gonna be exponetial. Take a freakin graphing calculator and see for yourself. And if you don't have a calc. do it by hand.<br />And as for what is causing dark energy... I have a thread explaining that. That I have to reply to by the way.<br /><br /><br /><br />Peace, <font color="yellow">and get a calculator <br /><br /></font></font></font> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[ianke]

Tigerbiten<br />* <br />** <br />**** <br />******** <br />**************** <br />ect, ect. <br /><br />This is exactly what happens in an expansion when distance is measured over time for the overall expansion.<br />However accelerating expansion is easier to compare with a fixed starting distance in each unit of time. <br />eg: <br />1ltyr will become 2ltyrs in a given time. then in the next unit of time(the same length of time) you measure how far the expansion of a 1ltyr of spacetime expands.<br /><br />If 2.00ltyrs the expansion is said to be constant<br /><br />If />2ltyrs the expansion is said to be accelerating<br /><br />conversely if <2ltyrs the spacetime expansion would be slowing down <br /><br />You could look for the acceleration rate in The overall expansion but the calculations (for an accelerating space time ) look more like <br />1l tyr yeilds 2+X ltyrs (x= the little extra vs the last time measurement)<br />next:<br />2+X yeilds 4+2X+whatever peice of 2X has expanded<br />etc etc<br /><br />Note: this is gets compounded by the fact that, if it keeps accelerating at and increasing rate, the X value Also Changes per unit time. <img src="/images/icons/crazy.gif" /><br /><br />So, for me anyway, it is simpler and easier to quantify spacetime acceleration if you use a the same starting distance and measure two different time periods of the same length. <br /><br />You could also use a fixed expansion (1ltyr becomes 2ltyr) and measure the time. Do this at two different times and measure the delta time to discribe a change in acceleration for the axpansion.<br /><br />Note: that whatever distance you choose to use is arbitrary as far as the starting distance is concerned (in the same fixed time) any expansion of space time IS linear.<br />eg:<br />1m expanding to 2 m<br />1ltyr "" "" 2ltyrs<br />1billltyrs expands to 2billion ltyrs<br />etc etc<br /><br />Also, you could use 2X, 100X, or 0.5X space time expansion, and in any given time frame and for that time frame alone ex <div class="Discussion_UserSignature"> </div>

 

[ianke]

FYI:<br /><br />After yesterday's discussion with Local_Group, I decided to try and get a grip on all of the CMBR findings. I'll have to admitt that the findings for CMBR along with theories like the contemporary version of the Cosmological Constant do make a compelling argument for the speeding up of the universe due to some force. (dark energy, vacuum energy, or whatevrer you want to call it)<br /><br /> I spent the entire night at it and the red shift issues I have, so forgive me if I rattle in my thought process this morning. However, where I was a "Dark Energy Agnostic" I will have to admit (although reluctantly) that I am becoming a "Dark Energy Convert". While the Dark energy value is at best a "derived Parameter" as stated in the Lambda-CDM model, when looking at the Cosmological Constant model it starts to become a more obvious choice to explain the whole issue of a driving force. <br /><br />The calculations have me quite spent from working with them last night, but I thought you guys, specially speedfreek, might like to know that I might be sending the white flag up after I get some sleep.<br /><br />I'll be bacK to see if I can make sense of it all tonight, but for now, good night all. <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[R1]

I'm glad to see us all discuss this to help us all understand it more clearly. I'm sorry<br />I'm actually having problems understanding yet another quirk, but Its about the same thing. <br /><br /><br /> I will try to use the same charting method used in the posts above, but I will only<br /> plot the distances between 2 to 8 let's say theres a galaxy or something at A,<br /> and B and C, their distaces are 2,4,and 8 lt yrs away from us:<br /><br />** (2 lt yrs away) a<br />**** (4 lt yrs away) b<br />******** (8 lt yrs away) c<br /><br /><br /><br />alright, now with the rate increasing (acceleration) the diagram is actually:<br /><br />d**+.5 (2.5 lt yrs away) (or2 + .5 + 0) <br />e*****+.1 (5.1 lt yrs away) (or4 + 1 +.1) <br />f**********+.4 (10.4 lt yrs away) (or8 + 2.2 +.2) <br /><br /> <br /> <br />in other words between d and e the acceleration result was .1 and the between e and f the acceleration result is .2<br /><br /><br /><br />then I get confused when someone says that the expansion of the universe<br />is accelerating as in d e f, because to say that it's accelerating means that between a point in the past and more recent point in time closer to the present the rate has increased, <br /><br />so considering that the observation of something x light yrs away is<br />really an observation of x years ago, my mind changes the words 'lt yrs away'<br />to 'yrs ago' automatically to get an accurate description of the change between a <br />point in the past and a more recent point closer to the present and I end up with<br />needing the universe to appear as in g h i <br /><br />g****+.2 (4.2 yrs ago) (or2 +2 + .2) <br />h*****+.1 <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

In short, yes, you are correct in your thinking.<br /><br />But (as usual!) the picture we see is a little more complicated. There are more points to consider.<br /><br />Firstly, seeing as we are having a hard time working out if expansion is indeed accelerating, it is reasonable to assume the acceleration is relatively slow. It is incredibly hard to detect any expansion at all at close range. We are having trouble working how far off the straight line the curve is (or if it is accelerating at all)!<br /><br />Then consider the sphere of observable space-time around us. If expansion is accelerating, the further away you look, the slower the rate was, but only by a slight amount (assuming it has always been accelerating).<br /><br />But the real issue is that, the light from objects has to pass through all the expanding space-time between the object and us! The light is stretched all the time it passes through expanding space. When the light leaves its source, it is not redshifted at all. As it journeys through expanding space it gets stretched. If the expansion accelerates during its journey it gets stretched at a larger rate.<br /><br />Lets imagine the acceleration in steps for simplicity. For an object 1 billion ly away lets say for example the light gets stretched by 10% during its journey. For an object 2 billion ly away lets say the light is only stretched by 9% until it reaches 1 billion ly away, where the rate changes to 10%. Lets say the light "value" when it left each object was 100.<br /><br />What we end up with is a 1 billion ly object with a redshift of 10% and a light value of 110. The 2 billion ly object ends up with a redshift of 9% + 10%. After the first billion light years its value is 109. After the second billion light years its value is 119.9. The further object already had a light value of 109 when its light passed the nearer object, and then both objects light was stretched by the same amount for the last part of the journey.<br /><br />So yes, with accel <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[R1]

interesting.<br />thanks speedfreek, I'm starting to understand it better.<br /><br />just as you were posting, in fact I was thinking about stretching the wavelengths of light.<br /><br />You're right, there's a lot of variables too, and the acceleration is not as easy<br />to measure as with a police radar gun.<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[emperor_of_localgroup]

Hahahaha, it's only a matter of time you'll be back in dark energy agnostic group as new findings surface. <br /><br />My hesitation about CMBR is, in this 13+ billion years of the universe, a million events could have taken place leaving absolutely ZERO traces for us to detect. Any one of these million events could have triggered CMBR. Do not forget 13+ billion years is a long long time.<br /><br />Mathematical models for any event are not hard to create. <div class="Discussion_UserSignature"> <font size="2" color="#ff0000"><strong>Earth is Boring</strong></font> </div>

 

[ianke]

John1R<br />don't forget the rest of the numbers<img src="/images/icons/cool.gif" /><br /><br />** 1*2<br />**** 2*2<br />****** 3*2<br />******** 4*2<br />********** 5*2<br />************ 6*2<br />************** 7*2<br /><br />Still linear<img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[ianke]

Hello emperor<br /><br />I am still not 100% on the dark matter. Just a little more comfortable with it in the Cosmological Constant model.<br /><br />That is not to say that I'm ready to join the "Dark Energy Monestary" <br /><br />I still think that have a lot of problems to overcome:<br /><br />1. There is still other possibilities that will fit the Observations without the use of dark energy.<br /><br />2. I'm still not 100% on weather the data really shows exactly what they propose.(speeding up....)<br /><br />3. Even the CMBR which they say has a "high degree of accuracy" could be shifted over time. After all, it is just another wavelenght of energy. This portion is NOT an area I know about well enough to really defend one way or the other.<br /><br />I guess that I am still skeptical when all is said and done.<img src="/images/icons/crazy.gif" /><br /><br />However, If I had to pick a theory I would go with the C.C. guys. The Calculations are a bear, but they at least show an eloquent argument. <br /><br />They still have a lot of work to do before I'd lay money on them in Lost Wages <img src="/images/icons/cool.gif" /> <div class="Discussion_UserSignature"> </div>

 

[ianke]

I just don't think I will be yelling so loud about Dark energy being magic anymore. <div class="Discussion_UserSignature"> </div>

 

[why06]

cool your a rock <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[ianke]

Hi John1R<br />Reguarding:<br />"the numbers are altogether messed up but at least I'm trying to show that the <br />acceleration of .0 should actually appear at the most distant point i, <br />because"<br /><br />While it would be easy to look at it that way, I hate to say this, but I have another wrench to through into the works. If you think of the time when light and matter could first come into existance, and I believe they consider that the end of the inflationary period, then It would seem to me that in that time the universe was still hauling ______ . In fact, there are those who think that it was decelerating up until 5 billion years ago. At that time mass had lost enough of it's hold in spacetime that the curve started going flat if not starting to inflate again. <br /><br />That will really make you scratch your head when you try to do a calculated plot. It seem to me that every time I start to get close to an understanding, that is when I realize I have to go back to square one.<br /><br />It is a little frustrating being curious. Isn't it? <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[ianke]

I'm Having a beer as we speek over it.LOL <div class="Discussion_UserSignature"> </div>