Black sphere traveling steadily at low altitudeI was alone in my back yard and heard an aircraft. I live right by North Perry Airport, so there are lots of small planes. I looked up and saw a jet climbing and behind/below it a black ball. They were both traveling northwest but the "ball" was much lower. I would guess it was roughly the size of a very small airplane compressed and traveling steadily at about the same speed as a small plane. I was stunned and thought it had something to do with being the 4th of July and at first thought it looked like it was following the airplane. We were also to be on high alert for terrorism this day. I watched it for about a minute with nobody else to yell to come see. I thought about calling 911 but thought they'd think i was nuts. I can't stop thinking about it so have been online and decided to post it. Maybe someone else saw it - had to have but maybe they'll read this.