I'm convinced it's "Construction of the Third Kind"...

During the 20th century, excavations at Stonehenge revealed that the structure was built in stages and that it dates back some 5,000 years,to the late Stone Age. The meaning of the monument, however, was anyone's guess -- until recently. Who built Stonehenge? What was its purpose? How did prehistoric people quarry, transport, sculpt and erect the giant stones? A new generation of researchers is tackling these questions, finding important clues in the landscape surrounding Stonehenge --prehistoric structures we can actually touch...NOVA 8pm

The Power of Song...

Two-time Oscar winning director Bill Guttentag presents SOUNDTRACK FOR A REVOLUTION: AMERICAN EXPERIENCE...the story of the American civil rights movement through music -- the freedom songs protesters sang on picket lines, in mass meetings, in paddy wagons and in jail cells as they fought for justice and equality. The music enabled African-Americans to sing words they could not say and it was crucial in helping protesters as they faced down brutal aggression with dignity and non-violence. This documentary is a blend of heart-wrenching interviews, dramatic images and contemporary performances by top artists, including John Legend, Joss Stone, Wyclef Jean and The Roots...8pm

American Masters: Marvin Gaye explaining "What's Goin' On"...9pm

His aim is still unerringly true...

Tonight our Britcom ARE YOU BEING SERVED moves to it's new home on Friday at 9pm, making room for another great music show on Saturday...LIVE FROM THE ARTISTS DEN...featuring Elvis Costello. His musical eclecticism and fiercely literate lyrics have earned him recognition as one of the most innovative and influential songwriters since Bob Dylan...9pm

And later at 10pm, Independent Lens asks the question "what was life really like in a Warsaw ghetto during Hitler's reign?" This documentary examines a classic Nazi propaganda film used by historians for decades to provide insight into the realities of life in the Warsaw Ghetto in 1942. The recent discovery of a second reel in an East German archive has thrown the veracity and intent of the Ghetto footage into question. It becomes clear as film and war historians examine the outtakes reel that Nazi propagandists staged elaborate scenes to mislead the general public about what was really happening in Warsaw.

...and he had the best line in "Aliens"...

Bill Paxton landed his first movie role in 1975's Crazy Mama, and spent the '80s playing small roles in a series of big movies. His first big lead was in One False Move, and a series of successful roles in movies and on TV has followed. His current projects include the hit HBO series Big Love and the Steven Soderbergh movie Haywire, scheduled for release later this year. Tonight, Evan Smith sits him down and gets him to talk on Overheard with Evan Smith...8pm.

Oh, and the best line from "Aliens"...after a jaw dropping - machine gunning run-in with the indestructible creatures, Bill's character exclaims..."I don't know if you've been keeping up with current events, man, but we just got our asses kicked!"

Watch the full episode. See more Overheard with Evan Smith.

It's good to be Emperor...but it's hard to come up with decrees...

The extraordinary story of China's 8,000 terracotta warriors begins two centuries before the birth of Christ. The First Emperor of China was preparing an extravagant tomb for his journey into the afterlife -- and decreed that he be protected forever by a monumental army...how was a terracotta army of this size made in less than two years using the technology of 2200 years ago? Secrets of the Dead's investigation shows that the Chinese may have Henry Ford beat by more than 2,000 years with their own assembly line...7pm

And at 8-m NOVA investigates the "Lost City of the Incas," the most famous archeological ruin in the Western Hemisphere. Why did the Incas build it on such an inaccessible site, clinging to the steep face of a mountain? Who lived among its stone buildings, farmed its emerald green terraces, and drank from its sophisticated aqueduct system? NOVA joins a new generation of archeologists as they probe areas of Machu Picchu that haven't been touched since the time of the Incas...

Hiding in plain sight...for a while...

In the aftermath of the killing of Osama Bin Laden, FRONTLINE presents two inside views of the fight against al Qaeda and the Taliban. First, Afghan journalist Najibullah Quraishi--who reported last year's award-winning FRONTLINE film Behind Taliban Lines--once again journeys deep inside enemy territory. This time, he gains extraordinary access to a band of militants and foreign fighters in Afghanistan who say they're loyal to bin Laden and are readying a Spring offensive against the U.S. Then, FRONTLINE crosses the border into Pakistan, where correspondents Stephen Grey and Martin Smith go inside "The Secret War" against the militants. They uncover new details of a CIA "private army" of militiamen launching kill raids against al Qaeda and the Taliban inside Pakistan. They also find new evidence of covert support for elements of the Taliban by the Pakistani military and its intelligence service, the ISI. At a safe-house not far from where bin Laden was killed, they make contact with one mid-level Taliban commander who tells FRONTLINE, "If they really wanted to, [the Pakistanis] could arrest us all in an hour."

He's right...this is when he's "so pretty"...

"MUHAMMAD ALI: MADE IN MIAMI" chronicles Cassius Clay's arrival in Miami in the fall of 1960 (fresh from earning a gold medal in the Rome Olympics), his life in Overtown -- a neighborhood that was considered "Harlem South" and a vibrant center of black entertainment and commerce -- and his affiliation with the famed Fifth Street Gym in Miami Beach. Over the course of the next few years Clay evolved both professionally and politically, piling up victories in the ring and adopting the black separatist teachings of the Nation of Islam. As "MUHAMMAD ALI: MADE IN MIAMI" makes clear, it was in this period that Cassius Clay became Muhammad Ali, and the boxing world was never the same again...9pm