I was watching this Youtube video, portraying a Fokker 70 taking off. I wouldn't have noticed if it weren't for a comment, but during spool up (~ 3:24 in the video), it appears as if the engine cowling is dilating. (See image below, if you don't want to watch the video). According to the person who left the comment, this is due to the pressure changing.
I'm having real trouble accepting this — though I do see it with my own eyes, I'm finding it more intuitive to believe something else is going on (I would think something related to the camera, though it seems to be well secured and I can't see any other perspective change).
In the end, since intuition is a poor tool for discovering the truth, I decided to ask:
Do turbofan engine cowlings really dilate due to spooling up, and is it really because of pressure difference? And is it the whole cowling or only the inlet that dilates?