Bigfoot, or Sasquatch, is one of North America's most enduring legends, with thousands of people claiming to have seen the giant ape-like creature. Here are the most famous Bigfoot sightings.
The "feel good" neurotransmitter serotonin is associated with mood.
Metallic spheres zooming past military jets, mysterious signals inside the world's largest telescope, and theories on why we have yet to make contact.
Earth's climate is warming dramatically, and the signs are all around us, from vanishing glaciers to zombie viruses awakening in melting permafrost.