We begin at the Supreme Court second big day of arguments over marriage equality the question today -- the federal government define marriages only between men and women. Our Supreme Court expert... See More
We begin at the Supreme Court second big day of arguments over marriage equality the question today -- the federal government define marriages only between men and women. Our Supreme Court expert Nightline anchor Terry Moran is there for all of -- today good morning Terry. Good morning George round two of gay marriage at the Supreme Court this is a social movement -- 21 century social movement. That is -- ride with astonishing speed at this court. Driven by activists by Hollywood in part and by young people especially. On social media and sitting inside their you can get the sense that the justices are not only grappling with a profound constitutional questions. But with the emotion of -- all as they come to terms with loved the ancient tradition of marriage. And whether they have the power to define it for all America. Happening so fast. The wave of increasing support for gay marriage in America especially among the young is crashing on the supreme -- -- justices in the average age 67 seem downright perplexed -- Problem with the case is that you're really asking particularly because of the sociological evidence from site. For us to go into uncharted waters. Why is seeking -- case. The Chief Justice Samuel Alito noting how gay marriage in America is less than ten years old you want. Us to step in and render a decision based on an assessment of the facts of this institution which is -- -- cell phones and the Internet. Across the country thousands are taking to social media changing their profile pictures to express their support for same sex marriage. This morning the justices will take up another case challenging the defense of marriage act. Which defines marriage under federal law as a union between one man and one woman. Edie Windsor is 83 years old and this is hurricanes. -- had 42 happy years with the love of her life the aspire. The two were married but when he had died in 2009. Edie got hit with -- almost 400000. Dollars in federal estate taxes a penalty she would not have had to pay. If she were married to a man if you could. -- -- the Supreme Court as they consider this case -- do you tell them. Want to marry into it any -- would -- being gay or straight we had a wonderful life together. -- wonderful life Edie Windsor there they'll take up her case in just a couple of hours now not the justices as far as we know how. Twitter or in mr. Graham accounts. But if they did they get a -- of what a 21 century American social movement this is. Check out beyoncÃ© -- -- Graham MacKay can put up a note that apparently she herself wrote it reads simply if you'll like it. Ought to be able to put a -- College many went on -- an accountant okay Terry thanks very much.
This transcript has been automatically generated and may not be 100% accurate.