All those couples on the dating prove what researchers now know means   Romance, quite literally, requires a certain chemistry. The love at first sight is no apocryphal cliche. Writer Jasbinder Alberts reports that all the researchers now know why one glimpse of the right person can let off a chemical reaction leading to romance. What happens after what? and why do some relationships succeed while others fizzle? It may be more magic than science. Robart Glenn Dowling visits with 60 famous couples who have overcome time and trials: depression, the death of a child, cancer, the stress of public life. Through it all of those , the marriages have survived--even grown stronger. Need is the thing that holds a marriage together over the long haul, says actor Daniyal O'Connor. If the need stops, the marriage stops.