From Wiki Gonzalez
Thread velocity is defined as the speed of a thread, measured in posts per hour. Certain teams' Game Chatters have high velocity, as do weekday afternoon Primer Lounges. Less commonly, a timely article in the Baseball Newsstand leads to a high-velocity thread.
Velocity is of course a relativistic property, meaning that it is experienced quite differently from various perspectives. A passenger in a thread with high velocity in comparison to other threads does not feel that he or she is posting any faster than normal. To the contrary, from this vantage point it appears as though the participants in other threads are posting quickly, even to the extent that they might post, age, die, and be replaced by new generations of posters before the poster in the high-velocity thread has reached the final post. This phenomenon is often (incorrectly) associated with double-posting.
If we hypothesize the existence of a vantage point that is truly fixed and immobile, such as that of a site owner, the relative velocities of each thread will be perceived not only as the various subject matters moving away from the site owner's gravitational influence at corresponding rates of speed, but also as an increase in the perceived weight and dimensions of the thread as its perceived velocity increases.
Thus a thread, or recurring series of threads, with very high velocity, relativistically appears to the hypothetical site owner as careering out of control, enormous, and extremely heavy, while it appears to the passengers in the thread to be the normal state of existence. In fact, to the thread's passengers, it is the site owner that seems out of control, enormous, and of suffocating mass.
It's all true because Einstein said so.