Live blogging: Maria Kon

Now we’re considering Rovelli’s strategy for quantum gravity.

Spacetime is dynamical.  Like other dynamical fields, it must be quantum in nature.  Put together, these criteria lead us to demand a background-independent quantum field theory with a field that in some sense represents spacetime.

In particular, Rovelli wants to put time “on a par” with other physical variables.

He starts from relationist principles, according to which fundamentally there are only physical objects and space is nothing more than a relational property of them.

A question: doesn’t Rovelli think that spacetime is one of the dynamical objects as the theory, which doesn’t sound like a relational property of other objects?

Kon’s answer: this is Rovelli’s broader picture of spacetime, not his specifically quantum picture.

Rovelli’s “partial observable” for time is highlighted (a measurement of local succession of events).  Are there conceptual conflicts between this picture and Rovelli’s commitment to relationism?  Not necessarily, since we might understand succession in purely relational terms.

But since observations occur at an instant, this particular temporal concept must be privileged, so it’s not clear that time is “on an equal footing” with space and other physical variables.

A question: how is time different from space in this way?

Kon: being at a particular place is defined by being at a particular instant.  But she can see the point—perhaps spatial relations could provide a framework for defining temporal ones in a similar way.

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