Doctor Who is a British science-fiction TV series that follows the adventures of a time-traveling alien, called the Doctor, and his human companion, as they travel through time and space in a spaceship, called the TARDIS (Time and Relative Dimension in Space), and courageously save the world time and time again.

Doctor Who first aired on BBC on 23 November, 1963 and was one of the first science-fiction stories to appear on screen: 3 years before Star Trek and 14 years before the Star Wars franchise. In 1989, due to falling popularity, the show was suspended. But 16 years later, in 2005, it was brought back to the screen with a whole new cast of actors and has been ongoing ever since. It is considered to be the longest running sci-fi show in the world, having celebrated its 50th anniversary in 2013.

But how has Doctor Who managed to survive for this long? What sets it apart from other amazing shows that are now over? What makes Doctor Who really unique, is that it does not have to rely on any particular actor to continue. When the Doctor is close to death, he is able to start a biological process within himself, called regeneration, that changes every single cell in his body, while still leaving his mind intact. Essentially, he becomes a different person: new looks, new personality, new everything. But one thing that never changes is his genius, and his sense of humor. This means, that every four years or so, when the actors playing the Doctor decide to move on to different projects and leave the show, the producers can find a new actor to take on the iconic role. So far twelve actors have played the Doctor.

Another reason the show has been running for so long is that there is no main storyline, it is very much episodic, each episode telling a story of a separate adventure. So as long as the writers of the show keep coming up with new planets for the Doctor and his companion to visit, and new alien villains for them to defeat, the show can continue forever.

Doctor Who has an unbelievably huge fan base all over the world, so big in fact, that the 50th anniversary episode aired in 94 countries simultaneously, earning it a Guinness World Record. There is also a large amount of music, inspired by Doctor Who, and since the series's renewal, a music genre called Trock (Time Lord Rock) has appeared. The most famous Trock band is Chameleon Circuit. They produce music exclusively about Doctor Who, and so far have released two albums.

Soon after Doctor Who’s appearance in 1963, novels surrounding the series started to appear. The first ever novelization came out on 12 November, 1964, almost exactly a year after the first episode came out. Since then over 150 novelizations and 200 spin-off books have been published, including some written by Neil Gaiman.

Doctor Who has been an important part of popular culture for over half a century now. The show is limitless, filled with possibility: you can go to Victorian London, or to Pompeii, or to the 51st century. It can be any genre: comedy, horror, fantasy, drama, sometimes all of them at the same time. It’s clever, and funny, and sad, and makes you think. The plots are well written, and sometimes you feel like you’re twisting your brain into a knot, trying to figure out the paradoxes. But most importantly it’s kind-hearted and beautiful. No doubt Doctor Who will remain a fan-favorite for many years to come.