Photographer Julian Tryba sent us this crazy time-lapse of Boston, which, actually, is not a time-lapse, but a layer-lapse: the objects in each sequence — buildings, vehicles, the sky — run at different speeds and times than others. That's because he has layered them, animating each layer separately.
He explains how he did it:
Traditional time-lapses are constrained by the idea that there is a single universal clock. In the spirit of Einstein's relativity theory, layer-lapses assign distinct clocks to any number of objects or regions in a scene. Each of these clocks may start at any point in time, and tick at any rate. The result is a visual time dilation effect known as layer-lapse.