[dhritzkiv]

20-30 feet change over what timeframe? The resolution of the chart data in the article is about 30 seconds. While I think the fluctuation is due to the accuracy of instrumentation, 20-30 feet change over the course of a minute seems like nothing.

[xvedejas]

That's significantly slower than a typical elevator, in fact. Slow elevators run at about 200 feet per minute.

[pbj1968]

My elevator takes almost a minute to go from the first floor to the second floor. I guess I have a slow one.