TAI is the 'UTC without leap seconds'.
UT1 is an evolution of solar time, and wobbles when Earth does because it's using the Earth and Sun (and other bodies) as a clock.
UTC is TAI with leap seconds added when UT1 drifts too far away.
UT1 is an evolution of solar time, and wobbles when Earth does because it's using the Earth and Sun (and other bodies) as a clock.
UTC is TAI with leap seconds added when UT1 drifts too far away.