What are the concepts in physics and astronomy that pose the most questions?
It seems most of them revolve around light, time and energy - at least if this rather non-scientific study is a guide.
You can get a better look at it here on Flickr.
It's a "word cloud" of the questions we've been asked by viewers. The bigger the word, the more often is comes up!
The questions were posed in response to the video below.
I've been putting some of the questions to our Sixty Symbols team... Their responses will be coming soon.