NORTH PHILADELPHIA (WPVI) -- A mysterious mass in the sky fascinated some North Philadelphia residents this weekend.Action News viewer Hector Garcia shot the video near 7th and Tioga streets Sunday afternoon.You can see a fast-moving, clear blob floating across the skyline.Some people believe the mass is some type of factory-grade soap bubble, due to the shimmering aspect, while others say it could be some type of transparent weather balloon.Action News even sent the video to our friends at AccuWeather, who had no hard explanation.Technically speaking, the blob is an unidentified flying object...or UFO.