Complex sentence: Left to run its course, this tidal drag would continue until the spin of the Earth and the orbital period of the Moon matched; however, the Sun will become a red giant long before that, engulfing the Earth.
Split into simpler sentences: Left to run its course, this tidal drag would continue until the spin of the Earth and the orbital period of the Moon matched. However, the Sun will become a red giant long before that, engulfing the Earth.