Expanding Spacetime in a Contracting Universe

[kmarinas86]

<font color="yellow">In this sense I see a Doppler effect on spacetime due to its' elasticity.</font><br /><br />Elasticity of space-time does not cause the doppler effect. The doppler effect is caused by a photon source moving relative to a photon absorber.<br /><br />Just what are the units for the "elasticity" of spacetime? Space-time isn't "solid" so to speak....<br /><br />And we shouldn't give the name doppler effect for something that has to do with gravity.<br /><br /><font color="yellow">"effect on spacetime due to its' elasticity." Wouldn't this effect hold true and have something similar to the doppler effect on spacetime between two masses?</font><br /><br />No.

 

[nojocujo]

I should have said similar to the doppler effect. I agree that you can't have a doppler for a gravitational effect. I don't know what the unit for an elastic spacetime does GR address the units or are they just inferred? What is an expansion redshift? Is that the intrinsic redshift?

 

[kmarinas86]

<font color="yellow">What is an expansion redshift? Is that the intrinsic redshift?</font><br /><br />A cosmological redshift that occurs relative to the hyperbolic space-time curvature, instead of being relative to an observer's motion. It is a real redshift, but not a doppler redshift. The velocity of galaxies relative to space-time causes doppler redshift, but that is not same as space-time expansion.

 

[Saiph]

The steady state theory (i.e. static universe) predates the BB, it predates the idea of an expanding universe.<br /><br />The compton effect is the scattering of light off of a free electron...it has nothing to do with gravity, only the presence of electrons.<br /><br />The earth's atmosphere has lots of free electrons. We typically look through more air and particulate matter in the 100 km or so to space, than the rest of the entire distance to the object. That being the case, light is more likely to scatter there, than anywhere else in it's route to us.<br /><br />Assume quasars are showing a standard cosmological redshift. I believe they do, as does mainstream astronomy, others may debate this though, so I'm stating it explicitly.<br /><br />If so, then they are heading away from us, as is nearly ever other galaxy. However, there are a few in the "local group" where expansion is weak (remember, closer you are, the less space-time expansion can interfere) the gravity of the galaxies (which is stronger closer you are) can hold eachother together against the "pull" of expansion. As such, the local group can orbit and even collide, since gravity on that short distance scale is stronger than expansion.<br /><br />Go beyond this distance, and expansion wins, making everything else "move" away. Other galaxies are also in clusters where mutual gravity holds them together, against the pull of expansion. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[eric2006]

"The compton effect is the scattering of light off of a free electron...it has nothing to do with gravity, only the presence of electrons."<br /><br />It has been a long time since I read this so please be easy with me if I am wrong. I was thinking that there were massive stars out there with intense strong gravity. This gravity being so strong that it has a slight tug on light leaving the star. Since light can only travel at one velocity it's wavelength is changed producing a slight shift. I always considered that to be due to the compton effect.<br /><br />"If so, then they are heading away from us, as is nearly ever other galaxy. However, there are a few in the "local group" where expansion is weak (remember, closer you are, the less space-time expansion can interfere) the gravity of the galaxies (which is stronger closer you are) can hold eachother together against the "pull" of expansion. As such, the local group can orbit and even collide, since gravity on that short distance scale is stronger than expansion."<br /><br />Are the only blue-shifting galaxies the ones in our local group? <br /><br />Another question. Is there another effect other than doppler to gauge with? The visible spectrum being so small I was wondering if there were other shifts in the EM spectrum.

 

[eric2006]

can you post a link to that thread.

 

[nojocujo]

The observed redshift has been measured to increase over time corresponding with the increased expansion? I would think that with an expanding universe that the redshift would not be perceptible within the timeframes of current observations. That is just a guess though.

 

[nojocujo]

Dr. Tod Strohmayer of NASA measured the gravitational redshift of a neutron star. I think this is what you are referring to.<br />I was thinking that there were massive stars out there with intense strong gravity. This gravity being so strong that it has a slight tug on light leaving the star.

 

[eric2006]

Thanks. I was looking it up this morning. It is called a gravitational redshift or Einstein Shift. I confused it with the compton effect.

 

[nojocujo]

You addressed an expansion redshift without addressing unit of measurement for elasticity of spacetime. I made an inference that due to the gravitational warpage by mass in GR that there must be a means to quantify that elasticity. <br /><br />The spacetime expansion indicating a stretching of spacetime?

 

[nojocujo]

This hasn't been proven but I think there would be two Gravitational redshifts one of the type already described and one caused by a local spacetime expansion caused by a gravitational wave and there is no evidence supporting this to date.

 

[vogon13]

Watching the redshift of a distant object change over time is just beyond current observational technology. These capabilities are under development and should produce results (IIRC) in the next 20 years or so.<br /><br />Understand the significance of this, actual observation of red shift changes of objects will highlight the deceleration (or acceleration) parameter. Theories will live and die by the results.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[nojocujo]

I didn't think that we could discern the cosmological redshift over time at this point so the Hubble expansion is just still a best guess except dark energy is supported by the Hubble expansion and it is not the simplist explanation.

 

[eric2006]

In the mid 1970s, American researchers observed a binary pulsar system (named PSR1913+16) that was thought to consist of two neutron stars orbiting each other closely and rapidly. Radio pulses from one of the stars showed that its orbital period decreases by 75 microseconds per year. In other words, the stars are spiralling in towards each other -- and by just the amount predicted if the system were losing energy by radiating gravity waves.

 

[kmarinas86]

<font color="yellow">The spacetime expansion indicating a stretching of spacetime?</font><br /><br />Perhaps. What exactly causes the expansion (streching)? Why is the hyperbolic curvature of space there? Does it have to do with how much matter is making an impression (compression) on time and space (i.e. creating positive curvature)?<br /><br />There is perhaps no way to know unless if we send experiments to outside our solarsystem.<br /><br />Is space time really elastic? Could it have plasticity too?<br /><br />We will have to use terms different than elasticity and plasticity if we want to be clear to the mainstream.<br /><br />GR talks about Graviationation waves. Not about the so-called "elasticity" or "plasticity" of space-time.<br />

 

[nojocujo]

The elasticity of the curvature of spacetime is defined by the Einstein tensor in GR.

 

[Saiph]

What you are reffering to is indeed graviational redshift. This also can't explain the cosmological redshifts for several reasons. One, it would create a much more "inconsistent" distance vs redshift relationship, as some light would pass by more objects than others. Two, if it's getting a significant redshift, it's also going to get a significant deflection and distortion (einstein's cross, gravitational lensing) and we see that, but it isn't to common. Three, it's only redshifted leaving the source galaxy. Any other galaxies it passes blueshift it on the way in, and redshift it back on the way out: no net shift.<br /><br />The only blueshifted galaxies are in our local group: correct.<br /><br />redshift is caused by several sources, gravitational, cosmological (expansion of spacetime) and "doppler". there are ways to tell the difference between them, from other clues as well as the redshift spectrum itself.<br /><br />All of them affect all wavelengths of light, it isn't just a visible spectrum effect. The reason we use redshift and blueshift is because we see visible light, not other types. And the terms are used to show that the light is shifted towards the red, or towards the blue end of the spectrum, not to designate any real color change. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[kmarinas86]

http://www.google.com/search?q="galaxies+are+blueshifted"<br /><br /><font color="yellow">Exploding the big bang<br />About seven local galaxies are blueshifted. The orthodox view is that they must<br />be moving towards us even faster than the universe is expanding, ...<br />ourworld.compuserve.com/homepages/dp5/explode.htm - 17k - Cached - Similar pages</font>/safety_wrapper>

 

[nojocujo]

Saiph,<br />Hubbles findingsregarding redshift and the conclusions drawn from the data made me feel warm and fuzzy for years. Then came dark energy and now if i have to accept both I may want to revisit what may have been a wrong turn. The key question is can GR still produce that same results observed By Hubble and everyone that has followed in a manner that does not require Dark Energy? So the we have to find what Dark Energy represents. Hubble defined a cosmological expansion and it worked for me. Then Perlmutter utilized the same data to redefine Hubble and added that the universe was not only expanding but there was an accelerating expansion. It was a semi reasonable conclusion based on decades of findings by other cosmologists/astronomers. I don't want to get off subject but there may be an additional redshifft associated with gravitational waves which is why I said semi.<br />If Hubbles model can support an energy that at this point is undefined and undiscovered except there is alot of evidence supporting that something repulsive appears to becreating and acceleration. This caused me to question Hubbles model. Einstien supposedly goofed and created his universe as a static model and had to revise GR to fit Hubbles model and came up with the cosmological constant and now we have put Lambda back into the equation and especially with Dark Energy.<br />I began to ask what would cause an acceration of the universe at this point in time with nothing new in the alleged manner observed and I had no candiadates. Robert Caldwell came up with Quintessence. He confused me. So sometime when things go awry you have to go back and see what might have gone wrong. Which means you revisit and try to rethink all those previous conclusions. If the universe were not static which Hubbles concluded and the redshift indicated that it was not static could it instead be contracting? If it were contracting how could you possibly have the same results regarding the redshift that have been

 

[nojocujo]

Can GR plausibly explain a cosmological redshift due to a spacetime expansion in a contracting universe eliminating the need for Dark Energy?<br /><br />To break it down further for a spacetime expansion to occur does it require a universal expansion? The standard model requires the universe be expanding but in essence a spacetime expansion is just a flattening of the curvature of spacetime and the reasonable conclusion is that the universe is getting larger and less dense additionally gravity on the inverse square has less affect. <br /><br />Matter through gravitational attraction aggregates matter and spacetime is warped by same. <br /><br />This aggreagtion of matter and warpage of spacetime continues without abatement until even energy can't escape these aggregations (blackholes). At this point even the energy captured adds toi the gravitational potential.<br /><br />The Einstein Tensor established a degree of elasticity for spacetime which is linked to the matter consumed in blackholes and time would stop when the apparent velocity of c is equal to 0 at the schwartzchild radius. At teh radius the gravitational potential increases regardless of the input whether it be matter or energy. At this point I hope we agree that spacetime as well as matter has been consumed since matter can't exist outside of spacetime. We do know that spacetime doesn't require matter to exist or it is a reasonable conclusion and even though a blackhole has consumed all available matter in the general vicinity does not mean it is finsihed eating. <br />Does the elasticity of spacetime (Einstein Tensor) allow a continued consumption of spacetime without additional matter inputs? <br /><br />If this were true then there is a possibility that a spacetime expansion could exist in a contracting universe. <br /><br />If matter was distributed in a homogenous manner throughout the universe the consumption could cause a redshift to appear to be homogenous as if it were a universal expansion. <br /><br />

 

[nojocujo]

Hubbles findingsregarding redshift and the conclusions drawn from the data made me feel warm and fuzzy for years. Then came dark energy and now if i have to accept both I may want to revisit what may have been a wrong turn. The key question is can GR still produce that same results observed By Hubble and everyone that has followed in a manner that does not require Dark Energy? So the we have to find what Dark Energy represents. Hubble defined a cosmological expansion and it worked for me. Then Perlmutter utilized the same data to redefine Hubble and added that the universe was not only expanding but there was an accelerating expansion. It was a semi reasonable conclusion based on decades of findings by other cosmologists/astronomers. I don't want to get off subject but there may be an additional redshifft associated with gravitational waves which is why I said semi.<br />If Hubbles model can support an energy that at this point is undefined and undiscovered except there is alot of evidence supporting that something repulsive appears to becreating and acceleration. This caused me to question Hubbles model. Einstien supposedly goofed and created his universe as a static model and had to revise GR to fit Hubbles model and came up with the cosmological constant and now we have put Lambda back into the equation and especially with Dark Energy.<br />I began to ask what would cause an acceration of the universe at this point in time with nothing new in the alleged manner observed and I had no candiadates. Robert Caldwell came up with Quintessence. He confused me. So sometime when things go awry you have to go back and see what might have gone wrong. Which means you revisit and try to rethink all those previous conclusions. If the universe were not static which Hubbles concluded and the redshift indicated that it was not static could it instead be contracting? If it were contracting how could you possibly have the same results regarding the redshift that have been observed fo

 

[eric2006]

Maybe the ancient white dwarfs (which are what explode in the Type I supernova) are different from what we expect.<br />But for now, it seems that every measurement astronomers make point towards an Open Universe.<br /><br />This is just the opposite effect expected, gravity should be slowing the expansion.<br /><br />The simplest answer for this overwhelming of gravity - the cosmological constant.<br /><br />Maybe Einstein was right after all, or maybe wrong twice.

 

[eric2006]

How the heck did this post get here?

 

[unlearningthemistakes]

computers are after all...<br /><br /><br /><br />??? <img src="/images/icons/rolleyes.gif" /> <div class="Discussion_UserSignature"> <p>pain is inevitable</p><p>suffering is optional </p> </div>

 

[nexium]

I forgot what the original thread was about, but my guess is differentiation occurs off Earth at least rarely, so we might find an extremely rare platimum rich "asteroid" Putting it in low Erarth orbit would require a prohibitive amount of energy and a slight error could easily total Paris, France or another major population center. Neil