Time travel is a difficult subject. It also happens to be a very popular subject of many stories in books, television, movies, video games, and so on. But human kind's limited understanding of the workings of time and the possibility of time travel (especially the limited understanding of the casual book reader, movie viewer, or video game player) leads to depictions of this subject being wrought with logical inconsistencies, paradoxes, and plot holes.

One of the most common problems with time travel stories is the creation of paradoxes. Of these, some of the most common paradoxes are the "predestination paradox", the "bootstrap paradox", and the "grandfather paradox" (or the "reverse grandfather" paradox). You're probably familiar with all of these, but you may not know them by name, so I'll take a moment to define them for you:

More photos have been released from the set of the new Silent Hill Revelation 3D movie. These images were captured by professional photographer Sara Collaton using a long-exposure technique in order to avoid the use of a flash and maintain the dark tone. The pictures are all of an amusement park set. Lakeside Amusement Park was an important location in both the first and third Silent Hill games.

The photos themselves are quite neat, because the long-exposure method gives a sort of blurry flatness to all of the objects in the photograph, giving them an almost video game-like quality. Wait a minute... Did I just compliment somebody for making a photograph of real life look more like a video game? I think I just did!

But, what if you compare the above images with some screen captures from the third game:

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.