I did some very basic calculations on the speeds of UFO'S ; For instance ; at 2000mph = divided by 60 mins = 33.33 miles / min. by 60 secs = 0.56 miles/sec. 5000mph = divided by 60 mins. = 83.33 miles/min. by 60 secs. = 1.39 miles/sec 10,000mph = divided by 60 mins. =166 miles/min. by 60 secs. = 2.7 miles/sec. 50,000mph = divided by 60 mins. = 833.33 miles/min. by 60 secs. = 69.45 miles/sec. So we can see why they can seem to " blink out " . Because within one second these craft will have gone at least a half a mile. Plus I think this refutes this " another dimension theory " as to why they just blink out or just disappear. The most puzzling thing about all this ; is that ; nobody has bothered to do these simple calculations before. These simple calculations changes one's perspective .