How does the B-theory of time not have a front edge. My understanding is that it is like a yardstick. Every inch exists simultaneously. The yardstick does not begin to exist at the first inch. However, it does have a front edge. Am I misunderstanding?

(April 27, 2016 at 9:38 am)SteveII Wrote: How does the B-theory of time not have a front edge. My understanding is that it is like a yardstick. Every inch exists simultaneously. The yardstick does not begin to exist at the first inch. However, it does have a front edge. Am I misunderstanding?

While I think purely spatial analogies are certainly imperfect here, it might be more helpful to imagine the surface of a sphere rather than inches on a yardstick. Every point of the sphere exists simultaneously, but at any one point you would describe your current position relative to others. For example, if you are in Chicago, you would measure your relative position to Tokyo differently than if you were measuring from Sydney. But regardless of which city you are measuring from, at no point would you consider yourself on an "edge" of the earth. Even standing on the North Pole where you would regard every other position as South of yours wouldn't be considered an "edge."

(April 27, 2016 at 12:41 pm)Time Traveler Wrote:

(April 27, 2016 at 9:38 am)SteveII Wrote: How does the B-theory of time not have a front edge. My understanding is that it is like a yardstick. Every inch exists simultaneously. The yardstick does not begin to exist at the first inch. However, it does have a front edge. Am I misunderstanding?

While I think purely spatial analogies are certainly imperfect here, it might be more helpful to imagine the surface of a sphere rather than inches on a yardstick. Every point of the sphere exists simultaneously, but at any one point you would describe your current position relative to others. For example, if you are in Chicago, you would measure your relative position to Tokyo differently than if you were measuring from Sydney. But regardless of which city you are measuring from, at no point would you consider yourself on an "edge" of the earth. Even standing on the North Pole where you would regard every other position as South of yours wouldn't be considered an "edge."

Are you saying that for every time T there is slice prior to T? If so, you have an actual infinite of past events and, I guess, an actual infinite of future events. Isn't that a problem because an actual infinite of anything is not coherent?

(April 27, 2016 at 12:53 pm)SteveII Wrote: Are you saying that for every time T there is slice prior to T? If so, you have an actual infinite of past events and, I guess, an actual infinite of future events. Isn't that a problem because an actual infinite of anything is not coherent?

I’m not sure how you jumped to that conclusion from the spherical analogy. But the B-theory suggests that absent an absolute universal “time T,” your measured intervals of time between events will vary relative to another observer who is in a different location or moving at a different rate or experiencing different gravitation (or acceleration), etc. Therefore, thinking of a set of all time segments prior to your “time T” may have subjective value, but it doesn’t have objective value. If all observational perspectives throughout the universe differ (whether slightly or significantly) and all are equally valid as Relativity would suggest, then how do you limit the number of temporal perspectives? In other words, considering all possible subjective reference frames based upon location, velocity, acceleration, mass, scale, direction, etc., what’s to limit the total number of time slices from all possible observational perspectives to a finite set?

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?

Hmm, great question!

My uneducated guess would be some sort of weird hub, perhaps a space/time anomoly, where you are on the cusp of two or more different areas. You'd observe things in a different way depending on which direction you looked from...

I don't know if that makes any sense or not

(April 27, 2016 at 4:07 pm)Time Traveler Wrote:

(April 27, 2016 at 12:53 pm)SteveII Wrote: Are you saying that for every time T there is slice prior to T? If so, you have an actual infinite of past events and, I guess, an actual infinite of future events. Isn't that a problem because an actual infinite of anything is not coherent?

I’m not sure how you jumped to that conclusion from the spherical analogy. But the B-theory suggests that absent an absolute universal “time T,” your measured intervals of time between events will vary relative to another observer who is in a different location or moving at a different rate or experiencing different gravitation (or acceleration), etc. Therefore, thinking of a set of all time segments prior to your “time T” may have subjective value, but it doesn’t have objective value. If all observational perspectives throughout the universe differ (whether slightly or significantly) and all are equally valid as Relativity would suggest, then how do you limit the number of temporal perspectives? In other words, considering all possible subjective reference frames based upon location, velocity, acceleration, mass, scale, direction, etc., what’s to limit the total number of time slices from all possible observational perspectives to a finite set?

You still have causes and their effects. Doesn't moving back through that chain you get to the first slice when time began at some point close to the singularity?

(April 28, 2016 at 6:46 am)SteveII Wrote: You still have causes and their effects. Doesn't moving back through that chain you get to the first slice when time began at some point close to the singularity?

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/

(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.

(April 28, 2016 at 11:19 am)Time Traveler Wrote:

(April 28, 2016 at 6:46 am)SteveII Wrote: You still have causes and their effects. Doesn't moving back through that chain you get to the first slice when time began at some point close to the singularity?

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?