
Editor's note: Buzz Aldrin, whose new book is "Magnificent Desolation," was one of the two American astronauts who were the first people to set foot on the moon.
[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/06/23/art.buzz.aldrin.moon.jpg caption="Buzz Aldrin walks on the moon in a photo taken by Neil Armstrong, his colleague on the 1969 mission. "]
By Buzz Aldrin
Special to CNN
(CNN) - Four decades have passed since the summer of 1969, when Neil Armstrong, Mike Collins and I flew America's first lunar landing mission.
The passage of time has not faded either the memory of that summer or the importance of what we achieved, for our mission was about more than just exploring the moon.
On July 20, 1969, Neil and I were peering out the window of our lunar lander, the Eagle, as it descended toward the lunar surface. The ship's computer was steering us toward a field of boulders the size of cars.
That same computer - with less power than today's pocket calculators - was signaling that it was overworked and dangerously overloaded. Our single tank of fuel was nearly empty as we approached the surface, invisible to us, cloaked in a cloud of swirling dust.
Neil took manual control and flew us toward a smoother terrain. Then, as the shadow of our landing gear appeared etched onto the surface in the gloom, a light on our console flashed that contact had been made.
"Houston, Tranquility Base Here," Neil radioed to the listening world back home. "The Eagle has landed!"
For more than two hours, we explored the moon's dusty surface. We could easily tell that the planet we had landed on was very different from our home. The horizon visibly curved away in the distance, a sign of the moon's much smaller landscape.

Here are the big stories on the agenda today:
Editor's Note: American Morning’s Tuesday audience remained committed to President Obama’s position on Iran, with many noting that the GOP was the only faction complaining about his response. Some were very disappointed to see the son of the former Shah of Iran, believing that his father’s dictatorship was the reason the current regime existed.
Many believe that President Obama’s approach to Iran has been appropriate. How do you feel about the GOP’s response? What did you think of the former Shah of Iran’s son speaking out today?
The city of Bozeman, Montana was asking people applying for city jobs to hand over their passwords to social networking sites – like Facebook and Twitter.
After the story spread online – the city backed down but the question remains: just how much privacy can you really expect online?
CNN's Alina Cho has an update on the story she first told us about a few months ago that involved two workers who got fired for what they said on Myspace.
[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/06/23/intv.pahlavi.cnn.art.jpg caption="Former Iranian Crown Prince Reza Pahlavi tells CNN there are reports some security forces have been joining protesters in the streets of Tehran."]
Iranian President Mahmoud Ahmadinejad will be sworn in for a second term sometime between July 26 and August 19, state-run media reported Tuesday. Many Iranians who have disputed the official outcome of the June 12 vote have taken to the streets to protest the results.
Reza Pahlavi, the former crown prince of Iran, says there are reports some security forces have been joining protesters in the streets of Tehran. Pahlavi’s father was the shah of Iran who was deposed in the Iranian Revolution of 1979. He spoke to John Roberts on CNN’s “American Morning” Tuesday.
John Roberts: The Guardian Council has ruled that the election results will stand and if there were irregularities they are not enough to swing the outcome of the election. There will be no new elections. What do you expect the reaction on the ground will be?
Reza Pahlavi: As we have all monitored the evolution of the situation, the supreme leader who has always been the final decider has drawn pretty much the line in the sand last Friday. And as such, I think the campaign that we have seen is now moving towards the direction of defiance and is going to be a resistance that will have to be sustained if indeed there's any hope for democracy in my homeland one day.
Roberts: There's debate as well over how much support the United States should give the protesters and the reform movement there in Iran. The White House is worried that coming out too strong in support could do more harm than good. What do you think?
Pahlavi: Well John, this is beyond a camp or another. This is not a question of election results anymore. This has become a defiance against a regime that has denied every right to its citizenry. When the chants on the streets in Tehran and other major cities in Iran and across the country are turning to “Death to Khamenei,” I don't think it could get as clear as that back home. The regime is now under question. The legitimacy is lost. The legitimacy now stands with the people. But there are also matters of ethics and moral responsibility, if I may say also. Something that the regime is trying to create [is] confusion between what could be considered as interference as opposed to standing for human rights and justice.
The president's response to Iran and his fight for health care reform... Two topics that will be front-and-center today at President Obama's first Rose Garden news conference.
Kiran Chetry got a sneak-preview from White House Press Secretary Robert Gibbs on CNN's "American Morning."

