No 2. Aurora
Also known in the southern hemisphere as the Aurora Australis and in the northern hemisphere as the Aurora Borealis, Aurora are charged particles from the Sun that have reached the Earth’s upper atmosphere and become excited. These occur mostly near the Arctic and Antarctic. These colorful displays of light are one of the most spectacular natural phenomena on earth.
Have a look at this amazing video:
No 1. The Hum
Hums are persistent and invasive low-frequency humming noise heard in many geographical locations around the world. Not all hums are audible to humans though. More famously a hum on the Big Island of Hawaii is typically related to volcanic action but mostly, the sources of such hums are never known.