I liked this better:

L1 - You've already started eating the sandwich, and only need to move your mouth and take another bite. (2 seconds)

L2 - There is a sandwich on the counter, so you need only find it, pick it up, and begin eating. (10 seconds)

RAM - You're near the fridge, but you need to open it and quickly throw together a sandwich. (3 minutes)

HD - Drive to store, purchase seeds, grow seeds, harvest etc. (1 year)

http://www.reddit.com/r/programming/comments/90tge/hey_rprog...

http://news.ycombinator.com/item?id=702713

http://www.infoq.com/presentations/Lock-free-Algorithms early-on gives good numbers on-machine.

I like this visualisation too: http://news.ycombinator.com/item?id=702713

This is a classic and wonderful way to learn and think about the junction of physics and computers.

Another one is https://news.ycombinator.com/item?id=702713