8. Vacuum Decay
The universe’s stability may not be guaranteed. Vacuum decay is a theoretical event where a bubble of “true vacuum”—a more stable state of reality—could suddenly appear and expand at light speed, annihilating all matter and physical laws in its path. This chilling scenario, discussed in outlets like Scientific American, stems from research on vacuum metastability and quantum physics. Thankfully, scientists think this is incredibly unlikely—but not impossible.