Today Google released a new version of Google Earth. The biggest change in the Earth exploration software is the addition of data from the world's oceans. Now you can scour the ocean floor and study its topography.I downloaded Google Earth 5.0 right away, and it doesn't disappoint. Rather than some simple blue-colored regions on the globe, you can now see the ocean's undersea mountains, valleys, and plains. Google has added a new layer for the ocean that shows all its nooks and crannies.

It's nifty. You can't explore the shape of coral reefs or anything, but all the major pieces of oceanic landscape are here. Being able to zoom out and see the entire Pacific Ocean lets you see exactly where the tectonic plates join up. It really gives a much more interesting view than the shading that was there previously.

Google also added a number of other features, including historical imagery, the ability to take tours, and a 3-D look at Mars.

The historical imagery tool lets you "move back and forth in time to reveal imagery from years and even decades past, revealing changes over time." Google has taken satellite imagery and is basically letting you look at the newest images (that are available to us mere mortals) and travel back in time by looking at older and older pictures of the same spot.

For example, I centered Google Earth over the Meadowlands complex in East Rutherford, N.J. It has a fairly current image that includes the new structures of the Xanadu complex. Using a slider, you can zoom back in time as far back as 1995 and see what Giant Stadium and the IZOD Center looked like back in the day, surrounded by all that marshy swampland rather than acres of new buildings.

Google Earth 5.0 is a free download for Windows and Apple computers.