At 11:09 -0700 4/08/2002, Tim May wrote:
>Think about time. Think of a "lattice" of events combining in
>various causal ways to product events, which then combine with other
>events, and so on. Judea Pearl has some of these causal diagrams in
>his book "Causality," and Lee Smolin has some in his book "Three
>Roads to Quantum Gravity." A basic idea, to be sure.
BM:
Yes. I got them for the subjective time through the S4Grz modal logic.
(S4 + the Grz formula)
TM:
>OK, but at some future time, when the light cones intersect, some
>event from that "other" light cone can help to make some event
>happen. For example, a supernova happening "now" at Alpha Centauri
>will take 4.3 years to make its presence felt here on Earth.
>
>Perhaps you see where this is going. Not-PAST is FUTURE, but
>Not-Not-PAST is not the PAST. Things get bigger, exactly as with the
>example above with the real number line and the open subset topology
>on it.
You should read "Dioderean Modality in Minkowski Spacetime" by Robert
Goldblatt (in his book "Mathematics of modality". Ref in my thesis).
Dioderean Modality = S4 + <>[]A -> []<>A
Note that S4 is really the modal "intuitionistic logic", cf Godel 1933.
--Bruno
--
http://iridia.ulb.ac.be/~marchal/
Received on Tue Aug 06 2002 - 03:46:08 PDT