"Annotate the web, with anyone, anywhere. We're a on a mission to bring an open conversation over the whole web. Use Hypothesis right now to hold discussions, read socially, organize your research, and take personal notes."
"Explore simultaneously in space and time with Time Machine
Each Time Machine on this page captures a process in extreme detail over space and time, with billions of pixels of explorable resolution. Choose a time machine and zoom into the image while traveling backwards or forwards through time. Select a Time Warp and the time machine's authors will take you on a guided space-time tour with text annotations explaining what you are viewing. You can even learn how to create your own Time Machines and Warps."