I think that what can be assumed is "13.7 billion years ago as far as the Earth is concerned."
It's no assumtion, this is an actual number based off the current rate of expansion, using general relativity.
I think that what can be assumed is "13.7 billion years ago as far as the Earth is concerned."
Right, the photon won't
experience time, or any change, but it's
travelled distance can be measured.
So, yeah, my guess is that the 13.7 billion year age is in reference to the Earth. Maybe our Sun? Or would our entire solar system (galaxy?) have about the same reference anyway?
It's based off of the furthest distance of the
observed Cosmic Microwave Background Radiation - CMBR, detected by the
WMAP.
"I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks
"I never knew there was another option other than to question everything"--Noam Chomsky
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