Blackout. But why?

Recently while watching television, the picture blacks us for a second or two. This happens frequently on any channel. It's very annoying and I don't know what causes it. To find out I posed the problem to the Internet. I was very surprised to find many, many other posts from other people who were troubled by the same problem, and were just as ignorant as I am as to why. What this means to me is that someone, possibly Comcast, (always creators of problems) or some other source is causing this problem and not acknowledging it. If anyone knows the reason for this malfunction, please let me know as I would really like to see an end to it.