In the past it seemed that men enjoyed standing around the barbecue turning the steaks.

Later everyone came to learn that this was bad, because turning the steak before it was fully cooked on one side allowed the juices to "get out". Legend has it that the meat must be "sealed" on one side to stop the juices getting out.

What are the juices that "get out" and where do they get out to?

If cooking on one side "seals in" the juices then why wouldn't it be better to quickly turn the meat to seal both sides before cooking?

Is there some advantage in only turning the meat once?