The pyramids of Egypt contain enough stone and mortar to construct a ten foot high/ five foot wide wall from New York to Los Angeles. Amazing to think that an ancient culture could have built these monstrosities!
Thank you John Medina for making this so clear. When we eat, food is converted to glucose - the body's fuel. The conversion process creates waste. This waste includes electrons which, left to their own devices, would collide with other electrons - creating of one of the most toxic agents known to mankind - free radicals. When we breathe we oxygenate our blood. Oxygen acts as a sponge, soaking up the excess electrons and removing them (through the conversion to carbon dioxide) before they can create cancer-causing free radicals. The brain, while occupying only 2% of our total body weight, consumes at least 20% of the glucose we produce by eating. This means the brain requires 20% of our oxygen supply in order to "sponge it" clean. Aerobic exercise increases blood flow and (therefore) oxygenation of the blood. More oxygen, cleansing of electron waste. Better clarity of mind. This is one of the many ways exercise contributes to better brain function. For more - read Brain Rules by John Medina. It's a page turner.