system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does major chords sound happy and minor chords sad?

Why does major chords sound happy and minor chords sound sad? Is there any real science behind it, or is it like that because it's always been that way? I also wonder about humanity's fascination with rythm. I have some theories but I wonder what you guys think/know. 
Would appreciate if you could give an actual ELI5 explanation, I'm going to try to explain it to some kids at work.
gpt
It's cultural. Major chords sound happy to you because you've been told it's happy since your early childhood. That said, Pharell William's "happy" is in minor chords (Happy Together by The Turtles too), whereas REM's Everybody Hurts is in major chords and Creep by Radiohead is mostly major too.