As far as I understand, loop quantum gravity treats space and time on very different footings. What I get is that in LQG time acts like a CPU clock in a computer representing a counter for the subsequent changes in the descrete structure of space. What worries me about this picture is, when time and space are treated so different in the foundation of this theory, why is it, that the role of time and space are almost completely symmetrical on the level of the Lorentz metric (only a difference in sign appearing)? As I understand, a goal of LQG must be to derive Lorentz invariance as an approximate feature of certain spin foam models. Not knowing, what the status of this is, does any body know, how the symmetry between space and time comes about in this theory then?