Interesting. I hear this is considered an extreme sport. True?
Hmm, I wouldn't say this is an extreme sport, or even a sport at all. 
Do you have loops for your marble run?
I do! Loops are the best and most interesting part of the marble runs, in my opinion.
I'll bet! Having them climb and do loops brings physics into the mix.
Yep, exactly! If I were super nerdy, I could see if I could collect some data on the velocities of each marble at particular points on the track. Unfortunately, I don't think I'm motivated enough to do that.
I would love to see these in person or even on TV.
You can easily find great videos of marble runs on Youtube.
Great idea! I forget about how many things YouTube has.
Yeah, YouTube is a treasure trove full of videos for any topic or subject you fancy. It's wonderful.