How big is our Galaxy.

objects at the limit of observability a billion years ago are no longer visible to us today

cavediver writes:Iblis is right... the cosmological horizon is precisely that which represents infinite red shift (recession at c) and the big bang. It's not a coincidence.

This is the point at which the cosmological constant

Yes, I'm sure you're right. Though of course we could be "small" and multiply connected...

Hi SG. Don't confuse the obs universe with "now", the comoving hypersurface we ride upon. The 78 billion lyrs is the size of the universe on that surface, though is obviously highly lambda dependent, so we don't really have a clue.

"All the pieces add up to 78 billion-light-years. The light has not traveled that far, but 'the starting point of a photon reaching us today after travelling for 13.7 billion years is now 78 billion light-years away,' Cornish said. That would be the radius of the universe, and twice that -- 156 billion light-years -- is the diameter. That's based on a view going 90 percent of the way back in time, so it might be slightly larger."

"For a wide class of models, the non-detection rules out the possibility that we live in a universe with topology scale smaller than 24 Gpc."

Iblis writes:That object itself is say 78 billion light years away now (whatever little that might mean once we give up simultaneity) and has aged whatever aging would apply to objects conceived of as moving away from us at a speed faster than light could be conceived of as aging. No way to ever check that answer though.

These clocks move at the same rate as our own

It is a common misconception that the observable universe is only 14 billion light years in radius because the universe is only 14 billion years old, and it follows logically that if nothing may travel faster than the speed of light, the universe may not have expanded at greater than the speed of light. However, the Special Relativity speed limit only applies to motion through space; space may expand faster than c. This occurs when space expands behind a photon in transit, and the photon may travel distance which is now greater than the Hubble distance, the distance beyond which objects recede at faster than the speed of light, or the traditionally and incorrectly defined edge of the observable universe[1].There is some disagreement as to exactly how large the observable universe is: a study of the cosmic microwave background radiation by Wmap in May 2004 states the universe is at least 78 billion light years in radius[2], yet the March 2005 issue of Scientific American cites a figure of 46 billion lys in every direction.In practice we can only observe objects as far as the surface of last scattering 300,000 years after the big bang when the universe had cooled sufficiently to permit electrons to bind to nuclei, which brought a halt to the Compton scattering of ambient photons.

Hubble's "law" isv = H x dwith the modern value of the slope, H, called the Hubble Parameter (sometimes called Hubble Constant, but as we shall see it is not constant):H ~ 20 km/s/million l. y.The precise value of the Hubble Parameter is a matter of very hot debate with different groups proposing values between 15 km/s/million l. y. to 25 km/s/million l. y. It is interesting to note that the units for the Hubble Parameter are 1/time and the current estimate corresponds to a time of about 15 billion years. What might this time correspond to?

These clocks move at the same rate as our own.

That's because relativistic effects only apply to objects in motion relative to each other.

good reason not to overly trust Wiki