T = 0

[petrushka.googol]

What would you rate as the most likely candidate for T=0 on the time axis of the Universe ?

 

- the Planck Time

 

- the time protostars formed

 

- the time hydrogen transmuted to heavier elements (useful to humans).

 

Please opine.

 

[derek w]

T>0

anything less than that does not exist.

[petrushka.googol]

T>0

anything less than that does not exist.

 

T= 0 is that point when time in space-time is perceived for the first time. (not at a singularity.) Mathematically T cannot be greater than zero without ever traversing zero.

[Mordred]

 

Usually at Planck Epoch 10-43 seconds forward. This is the region of our shared causality or worldline

Though this can be set different ie CMB forward. CMB being an ideal reference frame in Cosmology.

Edited March 15, 2015 by Mordred

[John Cuthber]

 

... is perceived ...

By whom?

[timo]

Naively, the Big Bang scenario gives you a dynamics for the distances between points: Distances between fixed points do increase over time, which is called the expansion of space. What is very interesting is that if you follow this dynamics into the past, then there is a point in time where all distances are zero. I would chose this Big Bang time as t=0. There may be a problem with this if some physics close to the so-expected t=0 causes the expected point to not exist (i.e. if the dynamics of distances is different close to t=0 then extrapolating today's dynamics through this region may cause nonsense results).

 

Sidenote: What you call "Planck Time" is probably what I would call "Planck Epoch". Planck time usually refers to the length of a time interval, not a time-stamp. At least in my understanding.