If you visit the diavlog page, you can find a link to the MP3 file containing the audio-only portion of the diavlog, right below the video window and list of topics. (You can also download video files (WMV or MP4), for anyone else who might be interested.)

Objects sufficiently far away are always moving faster than the speed of light, if the expanding universe is big enough. Dark energy is responsible for accelerated expansion: the apparent velocity of individual galaxies is increasing with time. “Inflation” refers specifically to accelerated expansion in the early universe.

Yes, we think that a’ and a” are both positive right now. That’s from real measurements. The Hubble parameter is a’/a, which is actually decreasing. although slowly.

Zero point energy is one possible example of dark energy. It produces effects through its influence on gravity (spacetime curvature). “Only differences in energy are observable” is not true once you include gravity.

It’s hard to measure velocities without using redshifts. You might look at Ned Wright’s tutorial for more info:

http://www.astro.ucla.edu/~wright/cosmolog.htm

[B](.5A)[/B]Is there anyway to prove that we are not in the center of the universe with a linear redshift-distance law as opposed to being in the center with a quadratic redshift-distance law?

[B](A)[/B]I was under the impression, that since anything outside the Hubble radius is receding at values above c{z>C}, current theory is that the universe is still inflating, albeit much much slower then right after the Big Bang. Is dark energy what is suppose to be driving this inflation?

[B](B)[/B]If the above is true, then that means that a’(t) and a”(t) are >0, has this been measured? Is this why Hubble’s constant is said to be decreasing? But doesn’t this contradict the inflation model, since if a’(t) is increasing exponentially (like I would expect if the expansion depends on the volume of the universe) the constant should have a steady value, whats going on?

[B](B.5)[/B]Is there any difference between dark energy and zero point energy? If not, how can dark energy actually produce any effects? I thought the only reason you could subtract out the infinities of ground states is because only differences in energy are measurable. But since it is producing changes, does this mean the zero point energy is interacting with something outside our universe that has a even lower ground state?

[B](C)[/B]Since the Freidman equations depend on a isotropic universe (k can only have discrete values), what methods do we have to measure the receding velocities of distant objects that do not depend on the redshift?