I picked up a tweet from Dr. Kelly Sennholz this afternoon saying that "The number of people protesting [in Egypt] today is the largest number in a political event in the history of mankind."
For some details on that event, go to Daily News Egypt and Al Jazeera English. And keep checking Azza Sedky's Egypt blog, which now has a Reuters report saying that these enormous demonstrations are going on in 38º (100º Fahrenheit) temperatures.
