> We can't phase lock real seconds to calendar seconds, because calendar seconds are a moving target. As the Earth's rotation slows, calendar seconds get longer

> We can't phase lock real seconds to calendar seconds, because calendar seconds are a moving target. As the Earth's rotation slows, calendar seconds get longer. Seconds that get longer are not acceptable in science. Sure you can, and yes they are. There can be a difference between calendar seconds and atomic seconds. For most applications the difference is irrelevant. People doing science can explicitly account for the differences. And since most time-keeping in science is much more inaccurate than the difference between the speeds of TAI and UT1R, those folks won't care. Most of the applications that do require very precise timekeeping actually only care about having a very consistent timebase, they don't necessarily care as much about the speed of time. So even if we steered GPS time by enough to use it as a broadcast source of UT1R, the majority of users who use GNSS to synchronize their measurements also don't care. The remaining handful that do care are going to be purchasing atomic clocks anyway, and there are dedicated mechanisms available to synchronize those to TAI.