(April 28, 2016 at 11:30 am)Time Traveler Wrote:

(April 28, 2016 at 4:55 am)Ignorant Wrote: B-theory seems very appealing. I know very little about it, but what I have learned certainly seems more consistent with what physicists have discovered about reality. A question occurred to me:

If all observational perspectives are equally valid, each one having an observation (experience?) of time relative to that perspective (and it seems like that may be the case), what sort of observational perspective (if any, this may be incoherent) could theoretically observe multiple perspectives simultaneously?

We can collect the data from multiple perspectives and analyze the differences, such as flying synchronized clocks in different directions as was done in the 1971 Hafele-Keating experiment which verified Einstein's Relativity predictions regarding time dilation (along with many other confirming experiments sense, including all the GPS satellites which have to take Special and General Relativity into account to be at all accurate), but I'm not sure there would be a way for a single observer to actually witness multiple perspectives simultaneously as you posit since you can't be two places at once.

Try telling my wife that

(April 28, 2016 at 12:16 pm)SteveII Wrote: I did not want to get into a debate on cosmological theories (and so hijack your thread). So you are saying that the universe is eternal in the past so there is no end to the causal chain?

I'm saying scientists don't believe there was a singularity.

(April 28, 2016 at 11:19 am)Time Traveler Wrote: The Borde, Guth, Vilenkin model which many apologists like to sight...

Oops, make that "cite."

(April 28, 2016 at 12:16 pm)SteveII Wrote:

(April 28, 2016 at 11:19 am)Time Traveler Wrote: What singularity? Cosmologists no longer talk about an actual singularity once quantum effects are taken into account, including Penrose and Hawking who originally put forward the idea. The Borde, Guth, Vilenkin model which many apologists like to sight as proof of an absolute beginning based on a singularity was not only disputed in the same year by Aquirre and Gratton, but as I've stated elsewhere, Vilenkin states their hypothesis merely attempts to prove, "that the expansion of the universe must have had a beginning." We are currently 4 billion years or so (by our subjective time measurements) into another expansion phase driven by currently unknown causes (called dark energy), but we wouldn't say the universe "began" 9.8 billion years ago at the beginning of this latest expansion phase.

Here is a good article discussing singularities by theoretical physicist Matt Strassler:
https://profmattstrassler.com/2014/03/21...ngularity/

I did not want to get into a debate on cosmological theories (and so hijack your thread). So you are saying that the universe is eternal in the past so there is no end to the causal chain?

It just means there is no good reason to think that there is a singularity where time suddenly ends in the past.

But what you call a causal chain is a subtle thing. The arrow of time is largely a statistical phenomenon, and if in our past there is a time of minimum entropy, it might be possible that if you go further back, you start going forward into a different future. I'm not saying this is proven to be so, just that such weird things are entirely possible. Our simple everyday notions of a linear smooth time likely break down at some point.

And why do you think the B theory of time is superior to the A theory?

(May 2, 2016 at 12:30 pm)SteveII Wrote: And why do you think the B theory of time is superior to the A theory?

I'm not sure if you are asking me or Alex. But if you're asking me, it's because of the empirical evidence supporting Special and General Relativity. This evidence tells us there is no privileged time, that simultaneity of events is relative depending upon each observer's reference frame. And it's not just me... most physicists and philosophers are relativists, finding the B-theory provides a superior explanation of reality.