1 thing i've only recently learned about was the possibility of the Earth's magnetic poles reversing in the near future. The Earth's magnetic poles reversing (where magnetic north becomes south, vice versa) is a normal occurrence, and occurs [usually] every 200000 years. However, it has been over 700000 since the last time the poles reversed. That, combined with the recent increasing speed of the magnet poles shifting, and a few other details such as some magnetic distortion in areas of the world, is beginning to lead increasing numbers of scientist to believe we are way overdue for a magnetic pole reversal, and that it could possibly even occur in the near future.
Why would a magnetic pole reversal be bad(besides everyone getting confused by their compass not working right)? The Earth's magnetic field is very important to most life on Earth. it is what protects our planet from deadly solar flares. If a magnetic reversal were to occur, then while the poles are reversing, Earth would have hardly any magnetic field protecting us (at best, maybe %20 of the magnetic field), for a period of about 5 years. Without the magnetic field protecting us, solar flares could cause grave harm to us. first, the solar flares would probably destroy most electronics, do to the electromagnetic pulse created by the flare. Second, cancer rates would skyrocket, probably killing off a huge chunk,(if not a majority,) of humanity. Third, there is also a chance that the loss of the magnetic field would cause some of Earth's atmosphere to escape off into space, thinning the air greatly; people would be getting attitude sickness even at sea level.
this wouldn't necessarily be the end of humanity i think, but it would definitely be pretty damn harmful