On this date 20 years apart, two milestones were reached that set the tone for human space exploration.
The Soviet Union took the first leap, surprising the world on April 12, 1961, launching air force pilot Yuri Gagarin into orbit -- a single 108-minute loop around Earth -- making him the first human to fly in space. And 20 years later, America launched the era of the workhorse, reusable space shuttle as Columbia flew its first mission with just two astronauts, John Young and Robert Crippen.
In 1957, they launched the world's first artificial satellite, Sputnik 1, which led to both superpowers vying to be the first to send a human into space and safely return him to Earth. Gagarin's death-defying trip put Russia on top.
"Basically, they beat us to it. They had the technology. The implication of that was that Sputnik had already been a wake-up call for the U.S., and this was like slapping the other cheek," said Dave Brody, science and space writer for Space.com.
"They seemed to say, 'We're here, we're players, we have the ability to do advanced technologies and science, and we're going to explore the universe, and we could put bases in orbit with military guys on them," Brody told AOL News.
A little over three weeks after Gagarin's monumental feat, the first American in space, Alan Shepard, blasted off on May 5, 1961, for a 15-minute, suborbital flight.
But it wasn't until 1969 that the U.S. took an even greater leap ahead of Russia when Apollo 11's Neil Armstrong became the first person to walk on the moon.
These days, after so many significant space flight achievements, there isn't the same sense of ultra-competitiveness between the two countries that once pervaded the space program.
"Fortunately, in the decades since then, we've acquired a more mature view of this, and now we all celebrate Yuri Gagarin and the Russians' ability to do that, first time out of the box, orbiting a human being," said Brody.
One former NASA rocket scientist has fond memories of the early days of the space race.
"I was living in Westchester, N.Y., and around 1955 we used to come down to the Hayden Planetarium in New York to see the 'Dawn of the Space Age' public lectures. So I had access to all that intellectual ferment," Oberg told AOL News.
Oberg spent 22 years at the Johnson Space Center in Houston in mission control, engaged in mission design work, including winning the Sustained Superior Performance award for coordinating the design of the complex first space station assembly mission.
When Oberg arrived in Houston in 1975, he worked on space shuttle flight software, so he was directly involved with the early days of the shuttle missions.
"Our team thought of ourselves as the heart surgeons of the flight control team. We weren't involved with all the technical details of launching. We'd come in after the launch and control other aspects of the flight. I've worked about a dozen manned missions that were very intense and specialized."
While the April 12, 1981, launch of the shuttle Columbia may seem as if it was a planned date, to coincide with Gagarin's flight 20 years earlier, Oberg says it wasn't.
"It was absolutely a coincidence," he said. "We were aiming for March, and it kept getting put off. On April 10, we did the final countdown and tried to launch, and the computers froze up several times."
- June 16, 1963: The Soviet Union's Valentina Tereshkova becomes the first woman in space.
- July 20, 1969: Neil Armstrong takes that "one small step for a man -- one giant leap for mankind," becoming the first man to walk on the moon.
- July 1975: The U.S. and Soviet Union team up for the first international manned spaceflight, the Apollo-Soyuz Test Project.
- April 19, 1971: The first space station, Salyut 1, is launched by the Soviet Union.
- Nov. 2, 2000: One astronaut and two cosmonauts meet on board the International Space Station (ISS) for the first time.
- April 2001: Businessman Dennis Tito ushers in the dawn of space tourism by paying millions of dollars to hitch a ride to the ISS on a Russian Soyuz spacecraft.
- Oct. 15, 2003: China joins the space race, sending its first manned flight into space.
Brody also quickly recalls the importance of Apollo 8, the first mission, in December 1968, to perform a trans-lunar injection -- a maneuver that sent the crew of Frank Borman, Bill Anders and Jim Lovell farther away from Earth than anyone else had ever ventured.
"It was the first time humans had left Earth orbit, and they did a once-around mission, orbiting around the back side of the moon to get a slingshot effect to help get them back to Earth," said Brody.
"It came at a time in history when we really needed a victory. It was the year that both Robert Kennedy and Martin Luther King were assassinated, and the Vietnam War threatened to tear the U.S. apart politically," he continued.
"And what eventually became known as Earth Day can trace some of its DNA back to Apollo 8, because that was the first time that a camera was turned around and pointed at the Earth. That shot of the Earth on the cover of the Whole Earth Catalog was the beginning of the global awareness that we all occupy spaceship Earth together. Apollo 8 did that, so that's a very significant one for me," Brody said.
Oberg also has fond memories of Apollo 8. "I hitchhiked to Florida to watch Apollo 8 blast off -- so far, I've attended a Saturn V launch, been at two shuttle launches and three Soyuz launches in Kazakhstan.
"Probably the most bizarre launch I've ever been at was a few years ago when I went with Robert Bigelow -- who's building inflatable [space stations] -- to an ICBM base in Siberia, where he had leased an Army surplus missile to launch it into orbit," Oberg said.
"So I got to go to a place where maybe 20 other non-Soviets or non-Russians had ever been to without being shot, and watch this rocket launch. It was awesome because of the ambiance: It was sunset, in mid-summer Siberia."
The three retiring space shuttles were involved in a fierce competition as several cities and states hoped to land one of the ships for permanent displays. On this special spaceflight anniversary, NASA Administrator (and former astronaut) Charles Bolden announced the winners of the shuttle sweepstakes. [See Video Below]
When Atlantis ends the 30-year shuttle program in July, it gets to stay at the Kennedy Space Center; Endeavour will head to the California Science Center in Los Angeles; Discovery's final home will be at the Smithsonian Institution in Washington; and Enterprise – which never made it into space, but was used in early shuttle glide tests – will end up at the Intrepid Sea, Air and Space Museum in New York City.
Perhaps the biggest surprise was that none of the shuttles were chosen to go to Houston, home of the Johnson Space Center, astronaut training facilities and Mission Control.
"It is sad and unfortunate that politics played such an obvious role in the placement of these retiring orbiters," said U.S. Rep. John Culberson, R-Texas. "The thought of an orbiter not coming home to rest at Space Center Houston is truly tragic."
After Atlantis brings down the final curtain on the shuttle program, it will leave the door wide open for the dawn of private space enterprise. Companies like Virgin Galactic and Bigelow Aerospace are poised to compete for future Earth-orbit industry and tourism dollars.
Brody says the public is ready and eager for space exploration to continue.
"Absolutely, particularly if the cost isn't being borne exclusively by the taxpayer, but is borne in some measure by the shareholders of the company that stands to profit by the success of those missions.
"We need private enterprise because it gives you competition, and competition is one of the forces behind evolution.
The next generation of spacecraft will be used for low-Earth-orbit (LEO) activities.
"The real challenge will be to fly people beyond LEO to interplanetary space," said Oberg.
"I think an asteroid mission would be a splendid step to make. It's just hard enough that it will kill you if you're not extremely careful, but it's not too hard. Trying to land on Mars now would kill you no matter how good you were -- we're not yet good enough, smart enough or able."