Some videos have images from blackboard, to see speakers anotations. You can move mouse over the image to zoom in the image.
The images are syncronized with the video, but if you don't like you can disable by clicking on the check box "Keep sync thumbnails and video"
Also, if you need to lock the image position you can click on the imagem to lock it. If you click again the image will be released.
Please, note that when you lock the image position, the images will not be syncronized again, unless you enable it again.
This is a interesting feature, when enable the intention is to avoid distraction from other elements on the screen. Everything, but the video, will become dark.
If you click on the dark area, everything will become normal again.
If you notice something wrong on the video, you can click on the link "Report Video" bellow the player and tell us what's wrong. It's important to keep everything running.
You can search using a couple of words, that will search on the title of the video.
special relativity
You can also search for tags:
tag:dark-matter
Of course, you can combine them, to search a word, inside a tag
energy tag:dark-matter
If you put together two or more tags, the results will match video that contains any tag.
tag:dark-matter tag:physics
Also, you can use person keyword, to search an speaker.
person:"Nathan Berkovits"