To illustrate this briefly, think of an important life event, perhaps your graduation. Now suppose that you have friends and family who live far away and will not be able to attend this great event in person. You can either send them a video of you walking across the stage or you can send them a photo of you receiving your diploma from the university’s president. The video shows the event as it unfolds, whereas the photo shows one point in the event—though no one would think that the entire graduation