Today marks the anniversary of quite a few historical events of significance.

Today, the American Civil War turns 150 years old, as we observe the anniversary of the April 12, 1861 attack by Confederate troops of Fort Sumter near Charleston, South Carolina. Although a grim occasion on its own right, this attack does have some silver lining, as it began the conflict that would eventually set in motion this nation's steps towards racial equality.

50 years ago today, on April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first human being to travel into space and orbit the Earth.

Today is also the 30th anniversary of the 1981 maiden voyage of the space shuttle Columbia, the world's first reusable spacecraft. It was a momentous and cheerful day for space exploration. The shuttle itself met a tragic end, when it disintegrated on re-entry during a mission, killing its seven crew and passengers over 20 years later. I'd like to take this moment to thank the brave men and women of NASA for the heroic work they do expanding the horizons of human knowledge and experience, and to offer my sincerest condolences to the friends and family of all such heroes who did not return.

Yesterday, the space shuttle Discovery landed on Earth for the final time in its 27-year long career. On Monday, it has been reported that actor William Shatner gave the crew their final mission wake up call:

"These have been the voyages of the space shuttle Discovery, Her 30-year mission: To seek out new science. To build new outposts. To bring nations together on the final frontier. To boldly go, and do, what no spacecraft has done before."

Discovery, which has been taking astronauts into space since before I was even conceived, is expected to be donated to the Smithsonian Institute's National Air and Space Museum following a decontamination procedure. It will replace the space shuttle Enterprise, which will likely go on loan to other museums.