Yes, I know this is not a very original title, but it's all I could think of. I'm a skeptical person (being an engineer and all) and although I love reading and listening to ghost stories, I've always thought that there is a scientific explanation for supernatural stories that I've heard. I don't believe in ghosts either. If there is no explanation, I just chalk it up to coincidence or observer bias.
That's what I thought until I experienced the following. Even though I still think that the vast majority of ghost stories and supernatural occurrences have real-world explanations, I am willing to concede that there may be things out there that cannot be explained. Now on to my story.
This happened during the final semester of my senior year of college (seven years ago). I only had to take two easy classes. My schedule was messed up because I had enlisted in the National Guard two years prior and Basic Training and AIT messed up my school schedule (I had to drop a bunch of classes because I started late and I couldn't catch up on all of them). I figured that my final semester would be really easy. But before the semester started, one of my favorite professors invited me to take his advanced assembly-programming class. This professor's classes were the hardest classes in the CS department. But you learned a lot. His class was the one class I did not drop when I came back late from training. Despite being late I was able to get a B in that class; a major achievement and one of my proudest moments. Due to my performance, he invited me to be a grader and a TA for his class. I did this for a year. After that year was when my final semester started.
Because this professor liked my work and thought I was capable, he invited me to take his advanced assembly-programming class. Now this class was no joke. It was really, really hard and you had to put in long hours. I knew it would be difficult, but I did it anyway. As I expected I was putting in long hours. I would frequently stay up late in the lab, sometimes being the only one there.
The lab I worked in wasn't old or anything. It was a new building, having been built within the last two or three years. Originally intended to be a shopping and business center, most of it stayed unoccupied because of the rather high rent, until the university bought it and made it part of the campus. The reason I mention it, is because the building was new, and it didn't have a creepy past associated with it as far as I know. Towards the end of the semester, I was working on my final project. My teammate and I were the only ones in the lab. It was around 1:30 am when my teammate called it quits and decided to go home for the night. I was on a roll and so I decided to stay and work on the final project. We were pretty much done; I just had to run the code through a few more test cases and fix a few bugs before we turned it in the following day.
My teammate left and I was the only one in the lab. Like I mentioned before, there was nothing out of the ordinary about the lab. It was a stereotypical computer lab with benches and computers. The only "old" things in the room were processors that we worked on (Motorola 68k's). I was sitting at the southern end of the lab. Behind me were glass windows (the ones that go all the way from the ceiling to the floor) and a door that opened into a balcony, that overlooked the street. The balcony ran along the outside of the building and had stairs that took you down to stores that were at the bottom of the building. There is a Borders bookstore there that I used to often buy hot-chocolate from while I worked on my projects (not a coffee person!). There was also another entrance to the lab, that was on the western side. It opened into a small lobby where there was a main door that opened out to an open-air area. From there, there were stairs that led down to the street.
I used to turn out most of the lights, except for the one in my corner because I didn't want to waste energy. The darkness didn't bother me. It was maybe a little after 2:30am or 3:00am when I was done with fixing the bugs in the code. I figured I would run through it one more time before heading back home. This is when things started getting... well, weird. I distinctly remember hearing a tap on the window behind me. To be honest, I was startled. Not scared, just startled, like when you hear something unexpected. I turned and looked around, not expecting to see anything really. Like I expected, nothing was there. It was just the glass window. There was nothing there. I shrugged and turned back; it was probably the cleaning crew or something. Either way, I didn't give it much thought.