::nothing to add but this is a good thread::
[QUOTE=Asympotically fat]
There is no minimum age. That is you can always pick an observer for which the amount of time experienced by that observer starting at the big bang and arriving at present-day Earth is as small as you like (but non-zero).
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From a photon’s perspective, time should not exist at all (infinite time dilation). Neither should length exist (infinite Lorentz contraction). In effect, from a photon’s perspective, no time has passed from the BB, and its experience of life is emission and instantaneous absorption.
Now I read somewhere that a photon thinks about 3 microseconds(?) has passed since the BB. Since nothing can travel faster, that would give a number for the “youngest” age of the Universe since the BB. I cannot find a cite, but I think I read it in SciAm.
It seems to me the right anisotropy is with respect to observed expansion, id est if you observe isotropy in red shifts (at cosmological distances), then you are rest with respect to the Big Bang. If you have always observed isotropy in red shifts, ever since the Big Bang, then your clock will read the proper time for that location, and that will indeed be the age of the universe.
Right, there are null or ‘lightlike’ curves, but these don’t represent observers. It is pointless talking about what a photon experiences.
Yes, this is basically correct, with the caveat that the stuff you’re observing won’t necessarily be in its maximal-proper-time frame, and so there will be a bit of noise in your measurement. It’ll be a very small discrepancy, though.
12 minutes. We were created with false memories of the past and everything positioned as if that past had existed.
Not sure you could prove that wrong.
Isn’t “1 year” a constant regardless of your frame of reference? A year is the time it takes for the Earth to go around the Sun. So no matter your frame of reference in the universe, if you used your local stopwatch to time one Earth year and then multiplied that by 13 billion, you’d have the age of the universe according to your local time. Is that correct?
But what about the standard time of a second:
So in our universe, there have been this many caesium radiation period durations since the Big Bang:
9192631770 * 3600 seconds/hour * 24 hours/day * 365 days/year * 13 billion
Would that equal the number of caesium periods in any reference frame? That is, if beings on planet Zargon measured the number of caesium periods since the Big Bang, would they get the same answer as us on Earth?
No. What you measure as “1 second” depends on your reference frame, and also the presence of a nearby gravitational well. For example, say a GPS satellite above the earth measures “1 second”, and you measure “1 second”, those two measurements are not the same, even though the caesium atom vibrated exactly that many times for both observers.
Living inside earth’s gravitational well slows down time for us. Physical processes flow at a correspondingly slower rate (as per an observer in outer space).
To get a more precise answer you would have to specify several things, i.e.: which class of observers? How do we construct their frame of reference? Do these observers ‘correct’ their observations for the effects of red-shift/blue-shift and signal delay?
It is very difficult though to think of a way in which it could be correct, except for specific observers, making specific observations in specific situations. For example Hubble shift causes a visual effect whereby one isotropic observer appears in slow motion to another isotropic observer, this effect has been observed I believe in supernovae.
The problem again is that we need to know what you mean by reference frames and also how we can compare ‘now’ between two reference frames (these aren’t questions with out answers, but matters of definition). However see what I’ve said previously about observers carrying clocks and how there is a maximal time since the big bang for an observer arriving at an event, but the time can also be arbitrarily small.
not to mention that when the universe was really really small, the time dilation due to the intense gravitational field would account
I see this poster has been banned, but to correct this point, gravitational time dilation doesn’t really make sense in this context. The definition of GTD implicitly relies on the existence of observers that are stationary in a gravitational field and in order for observers to be stationary in a gravitational field (at least in a non-arbitrary sense), the field itself must be stationary (i.e. there is no time dependence in the field). Secondly it relies on gravity ‘disappearing’ at infinity, so observers can asymptotically compare their observations to somewhere where there is no gravity. Cosmological models have neither of these features.