What actually are planets, asteroids and dwarf planets? Here, Dr. Robert Hurt from the Spitzer Science Center in California, touches upon this intriguing question. In addition, he addresses the status of Pluto and how it recently came to pass that, what was once considered our solar system's most distant planet, has recently been demoted and... why? Enjoy!

Experimenting with the physics of water in the weightless environment aboard the International Space Station. For more out of this world experiments please check out
physics central.

Fascinating footage, our journey begins in Alaska's Katmai National Park, both inhospitable and beautiful. We observe brown bears as they hunt salmon, track the rare glacier bear, and then continue south to British Columbia on our hunt for the rare Kermode bear, also called ghost bear or spirit bear.

Our journey begins in Alaska's Katmai National Park, both inhospitable and beautiful. We observe brown bears as they hunt salmon, we track the rare glacier bear, and then we continue south to British Columbia on our hunt for the rare Kermode bear, also called ghost bear or spirit bear.

Alex Bellos tells us about a far superior method of cutting a cake using scientific principles.

More stunning footage from Alaska shows, up close and personal, the brown bears in action - hunting for salmon and caring for their young. Enjoy!

Observe more stunning footage from Alaska of the bald eagle and the black bear. And finally catch a first glimpse of the rare glacier bear. Enjoy!

In summer, mother bears and their young cubs can be spotted on the plains near Hallo Bay in Alaska's Katmai National Park.

"Help us to complete development of the Ocean Energy Turbine designed to replace Fossil Fuel and Nuclear Energy Dependence." Back this project and make the world a better place.

Catch glimpses of sockeye salmon, also called red salmon, as they make their way upstream in a migration known as the "red flood." Also included is footage of dippers, which are some of the only songbirds that search for food on the bottom of a body of water.

In order to fatten up before winter sets in, brown bears feast upon salmon migrating upstream to spawn. Enjoy!.

In this episode, we see how the bears coexist with other creatures in their environment, and also learn about the role of the bear in Tsimshian lore. Enjoy!

The salmon that make it upstream mate and then die of exhaustion. Meanwhile, many other animals are lurking and waiting to feed.

Romantic chemistry is all about warm, gooey feelings that gush from the deepest depths of the heart... right? Not quite. Actually, the real boss behind attraction is your brain, which runs through a very quick, very complex series of calculations when assessing a potential partner. Dawn Maslar explores how our five senses contribute to this mating game, citing some pretty wild studies along the way.

In this final installment of the series, a white Kermode bear encounters a black bear while fishing. Observe their behavior. Look and see for yourself what ensues!