Alex & Sierra Perform "Gravity" by Sara Barielles on week 7 of THE X FACTOR USA 2013. This song also rose to number one on the iTunes chart less than 24 hours after that performance. It is one of six songs by the couple to be in the top 100 at the same time, a reality show record. Just Amazing! And the judges reactions, especially Demi, make it all the more powerful. Watch & Listen to Gravity.