What happens to Earth every 70 years?

Could you elaborate on the phenomenon that occurs on Earth every 70 years? Is it a natural cycle, or perhaps a more mysterious event? Have scientists been able to uncover the reasons behind this occurrence, and if so, what insights have they gained? Additionally, are there any observable changes or effects that accompany this event, and how do they impact our planet and its inhabitants? Lastly, is there any significance or importance attached to this 70-year cycle, and if so, what is it?