I dont understand what he means by time being emergent… The universe is (at least on big enough scales) a lorentzian 4-manifold and the causal structure is given by future lightcones. In this sense time is not well defined (because we have to locally choose a spacelike slice to define time locally) but under certain conditions there is a well defined notion of causality. Time is fundamental as a dimension of space time. On the other hand there is the problem of actually measuring time. For this to work we need a clock which somehow has to measure events. The clock carries entropy etc… If there are no events happening there is no time passing which can be measured. A clock measures periodic events and counts them. But how can you tell how much time has actually passed between to ticks of the clock? You cannot be sure that the event is actually periodic and I think this loss of periodicity is a measure for the entropy of the clock. In addition depending on the temperature of a system the amount of time it takes to compute 1 bit of information should change. Thus in hotter systems there is a faster information conversion rate (or maybe it depends more on the energy gradient) which suggests that the measured time passes faster in this case. The thing which confuses me is that in quantum mechanics there is no time operator (to inherently measure time) On the other hand there is a position operator which measures the position. The only thing you have is the Hamilton operator which tells you how quantities change with time, but time itsself is not a measureable quantity itsself on the quantum level unlike position momentum or energy. Im suggesting that since time is not fundamentally observable you can have two systems in one of them time is passing faster than in the other one but the energy „flows“ slower, then there would no way to tell the difference between those systems. Thats because time can only be measured by events and not by scale itsself.