Feeling like you're moving when you're really sitting still

I sit here, noding away, when I realize there seems to be a sensation of descending throughout my body. If I remain focused on the monitor, I can just know that I'm somehow moving downward, my entire body. Then, I look around, and the feeling disappears.

A few moments later, back on the monitor, I can feel it again. Right now, it seems to be going sideways. I feel like I'm tilting, leaning, and I almost want to fall over to one side. Finally, I can't take it, and have to move, to look elsewhere, make it go away.

But every time I go back to the monitor, it comes back... oh, go away.... please...

Then, out of nowhere, I notice that I'm moving forward. That can't be, can it? My foot's on the brakes! My other foot's on the floorboard! Panic sets in.

Then, I realize it's just that a car next to me has decided to back up for some reason. The subconscious view, out of the corner of my eye, of that car backing up has led my brain to think I'm going forward. It's such a weird feeling.

If this were happening to me in my computer chair, I might rethink the amount of time I spend on E2....

This also happens after a long trip on some gently and regularly rocking vehicle, like a boat on a calm sea or (again) a train.

Contrast this feeling with feeling like you are moving when in fact you should be sitting still, which happens during earthquakes.

Oh, yeah, nitrous oxide will do that to you, too.

I often get this feeling when I am in a tall building, especially at the UW-Eau Claire campus. The library was particularly bad for this. I'd be doing homework -or more likely- casually reading, and the floor would suddenly start to move around underneath me. I'd feel disorientated, and a little nauseous. After a few seconds, or a few pounds of pressure on my head, my vertigous senses would return to equilibrium and the effect would pass. I don't know what caused this-possibly the building bending in the wind, or an odd architectual design, or what-have-you. Of course, the problem could be internal-I've never claimed to have perfect balance, or even good balance for that matter.

From a physics standpoint, our bodies are not equipped to detect motion-only acceleration. Thus, if I am "feeling like I'm moving when I'm really sitting still", there are three explanations. A.) You are accelerating-either changing direction, changing speed, or both. Check your surroundings-are they moving? Would there be a source of the acceleration around you? B.) Your internal sensors think you are moving-have you been spinning? Are you sick? Have you had your inner ear moved/removed? C.) You are crazy. Go to the nearest mental health facility and explain the situation. They will help you. They are nice people. (Note: this is ONLY for cases for which there is no other cure).