Traditional lap pools are about 10 feet wide, though widths between 8 and 10 feet are common. (In competition pools, swim lanes are 2.5 meters wide, or about 8.2 feet.) You don't want to go too narrow with a lap pool.
The number of neurons in the brain varies dramatically from species to species. One estimate (published in 1988) puts the human brain at about 100 billion (10 11) neurons and 100 trillion (10 14) synapses.
New York: Scientific American, 1999: 3. | An adult human brain has more than 100 billion neurons | > 100 billion Please note that the answer listed here - over 400,094,800 - refers to the number of cells in the human brain.