What is causing the mysterious ‘worldwide hum'?

The mysterious worldwide hum is like a very loud, low sound that some people can hear all around the world, kind of like when your fridge starts making a noise you didn’t notice before.

Imagine you're in a big room with lots of other kids. Each kid is playing a drum, but instead of beating it fast, they tap it slowly and softly. If everyone taps their drums at just the right time, the whole room might start to feel like it's vibrating, that’s kind of what happens with the hum.

Sometimes, big machines deep under the ground or in the ocean start working hard, and they make a low sound that travels far away. It's like when your brother is playing his video game really loudly in the next room, you can hear it even if you're not looking at it.

It’s like how some kids in the class can hear the teacher whispering, but others can’t. The worldwide hum might be too quiet for most people to notice, but those who are listening closely, or have very sensitive ears, can hear it clearly.