The Science of Time

Saturday, April 26, 2019


What "time" is, is a very basic and fundamental question. And contrary to the "science is complete, or near complete" advocates, I think we are FAR from understanding our universe if we don't have a clue on such a basic feature of it.

If folks here aren't familiar with the issue -- there are to my knowledge 3 primary models of time.

The most common model for most of history was to treat time as just a convenient metric to refer to sequential state changes. This is often called the "A" model of time, or Presentism in philosophy. In this model, "time" doesn't really exist -- it is an invented concept by us to refer to the history of state sequences, and to project future state sequences. The only things that actually exist are the things of the universe, and they only exist in their "present" state -- hence"presentism".

The more common model among physicists today is Block time, or the "B" model of time. This model treats time as a dimension of a 4-D Space-time continuum. This is Einstein's model behind General Relativity. In Block Time -- the past, present, and future all have the same status -- there is no special feature to the present. And the future is already set.

A third model is Growing Time -- which treats the PAST as in Block time, but the future does not yet exist. The present has a special status as the edge of Growing Time. Growing time was developed as a "fusion" model -- an effort to find away to incorporate the best features of Block time and presentism in a better model.

Several recent books advocating for one or another of these time models:

https://www.amazon.com/Now-Physics-Time-Richard-Muller/dp/0393354814/ref=sr_1_21?qid=1554052463&s=books&sr=1-21

https://www.amazon.com/Singular-Universe-Reality-Time-Philosophy/dp/1107074061/ref=pd_sim_14_3/142-1644542-8390269?_encoding=UTF8&pd_rd_i=1107074061&pd_rd_r=e0f49f8f-53d8-11e9-b6b9-cd59af5e4b95&pd_rd_w=C6bGd&pd_rd_wg=435Rj&pf_rd_p=90485860-83e9-4fd9-b838-b28a9b7fda30&pf_rd_r=A4MCG724N1CV7NYNAZE6&psc=1&refRID=A4MCG724N1CV7NYNAZE6

https://www.amazon.com/Brief-History-Time-Black-Holes/dp/0816147736/ref=sr_1_2?keywords=a+brief+history+of+time&qid=1554052738&s=books&sr=1-2

These books provided fairly effective criticisms of the competing models of time:

* Block time provides no explanation of our sense of the present -- a theory of time which fails to predict or usefully understand the primary feature of time -- is a remarkably weak "theory".

* Block time is in conflict with all indeterministic models of Quantum Mechanics (which is most, or arguably all of them).

* Presentism appears to be in conflict with actual physics, in which all events and interactions have duration -- an infinitesimal approach to time's extent -- cannot usefully address how our universe seems to be coupled into longer periods than an instant.

* Block time is very useful in both relativity, and in modeling the outcomes of QM interactions, while presentism cannot support either. Using the "indirect inference to reality" model of science -- this is strong evidence for block time over presentism.

* Growing time gives the present a special status, addressing one flaw of Block time, but in growing time the present is absolutely SECONDARY to the past. But we don't seem to be able to interact with the past -- and the present seems to be far far more important than the past -- so a model that declared the inaccessible past to be "real", and the present is special in only a minor derivative way -- is still not a particularly useful model. Growing time also does not address the thick time problem for an instantaneous present.

My takeaway from my reading is -- we don't have ANY good time models.

B&B orig: 4/1/19