I just love watching what smart people come up with. The latest is an algorithm to figure out when Apple will reach its 10 billionth song downloaded. Barry Schwartz, Mike Butler and Alex Fierro came up with a way to predict when the company will reach the milestone. According to Schwartz, this is how they figured things out.

“To come up with a good estimation, we started by taking a look at Apple’s “countdown” page. The 10 Billion Song Countdown page features a really awesome countdown effect without a lick of Flash; it’s all done by moving a large background-image up and down with Javascript and CSS. By taking a look at the source code, we quickly discovered that the counter’s starting amount and rate of change is being loaded from a text file.”

You can see the counter on his Web site. The counter is down to 83 million and dropping. The estimated time to reach 10 billion is in 7 days, 11 hours.

Apple is holding a contest with a $10,000 gift card going to the person that downloads the 10 billionth song.