Regarding quasars not showing signs of time dilation.

[theouthouse66]

Here's the article

http://news.discovery.com/space/no-time-dilation-for-distant-quasars.html


So the distant quasar is more red-shifted than the closer one, which means the farther one is traveling at a higher velocity, makes sense. My thought is if the quasar is "riding" if you will, on a piece of expanding spacetime, maybe it is not time dilating because it is not moving through spacetime. Similar to the whole thing about riding a piece of warped space to travel faster than light. Any thoughts?

 

[Myslius]

I have similar thoughts about spacetime. Let's take the farthest known star. By our FOR, velocity for that star is near c. Time dilation reaches infinity. So we see very old star (a star that lived 14 billions years ago (and now is 28 ly away). But 14 billion years have passed, and now that star probably doesn't exist at all. Basically that star doesn't move in spacetime at all. It's the spacetime who moves the star.

Now let's take a star that we see 7 ly ago (2 times less). If the distance between that star and the star that we see 14 ly ago is 2 times less that means, that there is no time dilation for farther stars

 

[Jonathan Scott]

Here's the article

http://news.discovery.com/space/no-time-dilation-for-distant-quasars.html So the distant quasar is more red-shifted than the closer one, which means the farther one is traveling at a higher velocity, makes sense. My thought is if the quasar is "riding" if you will, on a piece of expanding spacetime, maybe it is not time dilating because it is not moving through spacetime. Similar to the whole thing about riding a piece of warped space to travel faster than light. Any thoughts?

I'm not sure what you mean, or even whether what you're saying is meaningful.

In general what we see primarily depends on the rate of change of the total length of the light path from the quasar. If it is increasing, regardless of the interpretation as to why, then we should not only see the intrinsic spectrum of the quasar to be red-shifted as a result, but we should also see any local variations in the region of the quasar to be time-dilated by exactly the same factor.

In this case, the experimental results suggest that the characteristic time of output variations in the quasar varies less between quasars than the factor corresponding to their spectral redshift. This primarily suggests either (a) that a significant part of the quasar redshift is not distance-related (that is, quasars have significant intrinsic redshift, a very controversial position taken by Halton Arp and his supporters) or (b) that the rate of local variation of output with time in the region of a quasar varies with the age of the quasar in such a way that more distant (hence younger) quasars vary faster, very coincidentally matching and nullifying the effect of the increased time dilation. Various other alternative explanations have also been suggested, for example if the observed variation is due to intervening objects rather than being local to the quasar (so the expected frequency of intervening objects would increase with distance), or if there is some experimental bias relating to the way in which time variation is observed at different distances because of the observation methods. However, one way or another, some odd results have been observed which are currently in need of a good explanation.

 

[Jonathan Scott]

I have similar thoughts about spacetime. Let's take the farthest known star. By our FOR, velocity for that star is near c. Time dilation reaches infinity. So we see very old star (a star that lived 14 billions years ago (and now is 28 ly away). But 14 billion years have passed, and now that star probably doesn't exist at all. Basically that star doesn't move in spacetime at all. It's the spacetime who moves the star.

Now let's take a star that we see 7 ly ago (2 times less). If the distance between that star and the star that we see 14 ly ago is 2 times less that means, that there is no time dilation for farther stars

Sorry, I can't make sense of this, but as I already mentioned, an increasing light path from a distant object causes both redshifts in intrinsic spectrum and time dilation in intrinsic time varying processes, both involving exactly the same factor. If the relative factors do not match for different collections of quasars this suggests that either the objects have different intrinsic redshift or that the time varying processes are different for some other reason (or both).

 

[bcrowell]

Here is the actual paper:http://arxiv.org/abs/1004.1824 Here's a quote from the abstract:

Several explanations are discussed, including the possibility that time dilation effects are exactly offset by an increase in timescale of variation associated with black hole growth, or that the variations are caused by microlensing in which case time dilation would not be expected.

Neither of these two explanations is of the "OMG, relativity is wrong," or "OMG, cosmology isn't what we thought" variety.

My thought is if the quasar is "riding" if you will, on a piece of expanding spacetime, maybe it is not time dilating because it is not moving through spacetime. Similar to the whole thing about riding a piece of warped space to travel faster than light.

I assume you're thinking of the Alcubierre drive? http://en.wikipedia.org/wiki/Alcubierre_drive No, it's not a spacetime that could occur naturally.

By our FOR, velocity for that star is near c. time dilation reaches infinity.

Our frame of reference doesn't extend over cosmological distances. That's why there's no uniquely defined way of saying how fast a distant quasar is moving "now" relative to us. In the most commonly used coordinates, the coordinate velocities of the most distant galaxies that we can observe are greater than c. See http://arxiv.org/abs/astro-ph/0310808

 

[Vanadium 50]

I think there is also the assumption that QSO's are in some sense identical, at least in their light curves. I think that's at least questionable.

 

[bcrowell]

I think there is also the assumption that QSO's are in some sense identical, at least in their light curves. I think that's at least questionable.

Yes, and that's made explicit in the abstract of the paper: "Several explanations are discussed, including the possibility that time dilation effects are exactly offset by an increase in timescale of variation associated with black hole growth, [...]"