Some realizations about fluid dynamics based on observations about the real world.

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Motion is relative (obviously): a window open on my computer showed scrolling credits and beside it I was browsing a Wikipedia article and if I scrolled the wikipage with the credits and watched the wikipage the credits appeared not to be moving.

Fluid dynamics: with the fan on in my room some papers on a shelf rustled but did not fall off for hours. Then, with the door open and the position of the papers undisturbed, the papers fell to the floor. This suggests that the fact the door was open caused some change in the movement of air in the room and thus the papers were inclined to fall.