Only a handful of people have traveled to such staggering depths. One of them is movie director James Cameron, who using a state-of-the-art vessel, dropped 35,000 feet, or about 7 miles, to the deepest place on Earth -- the Challenger Deep in the western Pacific Ocean.
DPI stands for dots per inch. Depending on the mouse make it will have certain presets (e.g 3000, 6000) and pressing it will cause your mouse to cycle through them. The higher the DPI , the farther the cursor on your screen will move when you move the mouse.
For images viewed on computer screens, scan resolution merely determines image size. The bottom line is that dpi or ppi means pixels per inch, which means that if you scan 6 inches at 100 dpi (or 1 inch at 600 dpi), you will create 600 pixels, which will display on any screen as 600 pixels in size.