John Timmer posting in Wired (here) has the stat, Lest we get too enamored with our technological prowess, however, the authors (Hillert, Lopez) make some comparisons with biology. To put our findings in perspective, the 6.4*1018 instructions per second that human kind can carry out on its general-purpose computers in 2007 are in the same ballpark area as the maximum number of nerve impulses executed by one human brain per second, they write.
Terrance Sejnowski (here)illustrates how big 10 to the 15th power is with: How many synapses are there in the brain? Two neurons can communicate with each other at a synapse, which is the computational unit in the brain. The typical cortical synapse is less than a micron in diameter (10[-6] meter), near the resolution limit of the light microscope. If the economy of the world is a stretch for us to contemplate, thinking about all the synapses in your head is mind boggling. If I had a dollar for every synapse in your brain I could support the current economy of the world for 10 years. Cortical neurons on average fire once a second, which implies a bandwidth of around 10 bits per second, greater than the total bandwidth of the internet backbone.
Many things I read assume that the brain is large but not huge; complicated but not probably the most complicated thing that science has begun to study. We need to get a sense of perspective on these things. THE BRAIN IS VERY BIG AND VERY COMPLICATED. The other idea that we need to have perspective on is WE HAVE ONLY STARTED TO UNDERSTAND THE BRAIN. For example, we are only now finding that the gap-junctions between glial cells add to whole new huge level of brain function and of astronomically large numbers.