Well here's a fun time waster courtesy of those crazy (and possibly evil) geniuses over at Google.
Google's wizards have created a handy dandy time line that lets you see when certain genres of music began and how the music of those genres have stood the test of time. The best part is it's completely interactive and you can move around and look at sub-genres in each genre.
This visualization shows which albums from past eras are still in our music libraries today.
Dig deeper into the chart to highlight key artists in each genre and read their stories, and navigate to Google Play to hear their music. For example, by clicking on the Metal stripe, we can see the handoff from Classic Metal to Hair Metalto Alt Metal within the growth of the overall genre, as well as some of the most popular artists that composed each subgenre.
It's very easy to get sucked into playing for far longer than it seems so be sure that you don't have any appointments or food on the stove or something when you start digging into this thing.
Visit the Music Timeline or Google's Research Blog to find out exactly what the timeline is for.