Save guides, add subjects and pick up where you left off with your BBC account. However, many years ago, the Earth looked very different to how it does today. Around 250 million years ago ...

To mark Earth Day, NBC’s Brian Cheung joins TODAY to break down numbers and facts about the blue planet, including how it got its name and how many miles food may travel to get to your plate.

Sound as we know it does not exist in space. That’s because, on Earth, sound mainly travels to our ears via vibrating air molecules. Because space is a vacuum, meaning there is no matter at all ...