Sonic Boom

Who says you never learn anything watching television?  Well, I usually do.  And this week I was proven wrong.  I was watching a documentary on my flight over to Hong Kong yesterday on whips – as in bullwhips.  Apparently, a whip “cracks” not because the leather snaps against itself, but because the end of the whip breaks the sound barrier.

I dug around to see if this was actually, conceivably true.  Indeed, bullwhips are designed so that the handles are heavy and the “cracker” at the end of the whip is very light.  The initial wave of energy sent through the whip by swinging the handle remains constant, while the mass of the whip declines.  The only way to preserve kinetic energy is for the whip to travel faster per the formula E  = mv^2/2.  You don’t actually need the cracker to break the sound barrier; it will just make the sound louder.  You can actually break the sound barrier by  just twisting a wet towel and cracking it against one of your friends.  Now you know why it stings so bad.

For the sake of improving my technical prowess, I embedded of a video with a record-holder in whipping.  I wonder if anyone has ever asked him if he should wear earplugs while whipping.  Or, since he says he is looking for a career change, if he has considered looking into pornography.

Not Every Fourth Year Is A Leap Year

I had to categorize this post as Trivia because the information contained in it will affect very few people alive today (unless you are an avid historian or user of Microsoft Excel).  It turns out that we were all misled as children – not every fourth year is a leap year.  Since the solar year is actually less than 365.25 days, closer to 365.24, there are several other adjustments that need to be made.  Notably, only the beginning of every century that is evenly divisible by 4 is a leap year.  In other words, 1700, 1800 and 1900 were not leap years, but 2000 was a leap year.  2100 will not be a leap year, which will make it that much easier for me to reach the age of 120.

I was reading an article the other day about how in its early days, Microsoft encoded a date/time error into Microsoft Excel.  They assigned a number of 59 to February 28, 1900 and a number of 61 to March 1, 1900.  Microsoft has since “corrected” the error by assigning the number 60 to February 29 1900 (you can try it yourself).  Unfortunately, February 29, 1900 never occurred.