Last weekend, we celebrated Halloween in the U.S., and by Sunday evening, retailers had popped up display after display of Christmas trees, snow globes, inflatable snowmen, and other symbols of festive December holidays. And chances are, when the holiday-themed toy commercials hit the television this past week, you asked yourself, “Where did the time go?”

Here at Wolfram|Alpha, the holiday countdown is always on! Wolfram|Alpha knows the dates of many holidays and observations from around the world, from Children’s Day in India to the anniversary of the day the Berlin Wall was opened. Couple that data with Wolfram|Alpha’s ability to calculate dates, and you have a swift tool for counting down to a special day or answering queries such as “number of days between Thanksgiving and Christmas”.  And because some similarly named holidays are celebrated on different days in different countries, Wolfram|Alpha will return the appropriate date based on the location of your IP address. So for example, if you’re located in the U.S., Wolfram|Alpha knows that this year, Labor Day was on September 6, and if you’re in the U.K., Labor Day was on May 1.

And if you’re really in the spirit, you can grab one of these simple holiday countdown widgets for your website or blog. This simple widget includes a countdown to Thanksgiving, Chanukkah, Al-Hijra, Christmas, Kwanzaa, and New Year’s Eve in the U.S.

And since Wolfram|Alpha Widgets are customizable, you can create personal widgets that include your favorite popular holidays or private events, such as Fido’s birthday.

Wolfram|Alpha Widgets are just one more way you can share some holiday cheer on your blog and with your social networks. What holiday or special day are you counting down to?

Four hundred years ago, on January 7, 1610, Galileo pointed his telescope at the planet Jupiter and discovered that it had its own moons. This discovery changed our perspective on the universe.

Prior to Galileo’s discovery, the Earth-centric Ptolemaic system was the standard view of the cosmos where Earth was the center–heaven was above and Earth was below. Copernicus had proposed a heliocentric model, but it was a mental exercise meant to simplify the complicated Ptolemaic system. Galileo’s discovery was the first one that showed evidence that something was orbiting a body other than Earth. If Jupiter had things in orbit around it, why couldn’t other bodies?

At the time telescopes were cutting-edge, and only a few people had them. What Galileo did was an instructive example on how to combine technology and curiosity.

Today you can recreate the moment with today’s technology by typing “Jupiter” into Wolfram|Alpha.

Among the pods about Jupiter, there is a graphic showing the current configuration of the so-called “Galilean moons”, the ones Galileo saw 400 years ago: Io, Europa, Ganymede, and Callisto.

Type “Galilean moons” to find out more about them. Or for historical curiosity, try “January 7, 1610” and find out more about that day.

You can even virtually recreate Galileo’s observations for yourself. Here’s how he depicted what he saw 400 years ago on the night of January 7:

And here is what he saw a few days later:

In Galileo’s diagrams, the circle represents Jupiter, and the asterisks represent the moons he observed. He didn’t know they were moons until the second observation, when they had changed position. More »