The "bottomless" chasm is as much a staple of the Star Wars universe as the lightsaber. It's a wonderful symbol for that world's vast, endless technology and how small it can make a person feel. Nobody who watched the above scene as a kid was thinking that consciously, but we felt it when Luke, crushed by the revelation from Vader, tumbled down into it, falling, forever ...
... onto a bunch of used garage sale mattresses.
That behind-the-scenes pic is from the coffeetable book The Making of Star Wars: The Empire Strikes Back. Usually it's cool to see the inventive wizardry that went on behind the scenes at Lucasfilm, but now I can't watch that scene without picturing the big pile of smelly mattresses just below Luke that appear to have been collected from various alleys around town.