Until now, Google Earth showed a single image of any location. Displaying one image is fantastic for exposing the intricacy and majesty of planet, but it reduces each location to a single snapshot and ignores the rich historical context of place. Now, Google Earth 5.0 lets you "go back in time" and observe changes to the landscape of the planet, announced Google LatLong blog.
To transition to historical imagery mode, click on the clock icon in the toolbar:
The historical imagery time slider will appear just beneath the toolbar. The time slider allows you to change your view to imagery which is older than the date shown on the slider. The tick marks on the slider represent images in our database that are available for your current view. You can move the slider back and forth along the timeline or use the arrow buttons in the upper left corner to step from one date to the next. If there are just too many ticks marks grouped together try using the zoom in and zoom out buttons to expand or contract the timeline. That's all there is to it! Now you can fly around to different spots in the world and explore our archives to see what imagery we have to show of the location.