Harvard University neuroscientist Jeff Lichtman, who is attempting to map the human brain, has calculated that several billion petabytes of data storage would be needed to index the entire human brain. The Internet is currently estimated to be 5 million terabytes (TB) of which Google has indexed roughly 200 TB or just .004% of its total size. The numbers involved are astounding especially when considering the size of the human brain and the number of neurons in it.
Source: Knowledge Doubling Every 12 Months, Soon to be Every 12 Hours – Industry Tap
