Life's Little Mysteries

To the naked eye, the night sky reveals only one moon. But how many moons have ever orbited Earth?

Which living and extinct animals have the strongest bite forces on record?

Dogs commonly tilt their heads, but is it a sign of intelligence, or does it mean something else entirely?

Sand is difficult to walk or run across. But why?

The brain doesn't have its own pain receptors, so why do headaches hurt so much?

The bottom of the Mariana Trench is about 35,876 feet (10,935 meters) deep, making it deeper than Mount Everest is tall.

Not all asteroids are planet-killers — most are tiny and others are huge. So what are the largest and smallest asteroids in the solar system?

Animals, especially those on land, can't grow indefinitely. The reason has to do with the square-cube law.

Octopuses are odd: They have more than one heart and copper-rich blue blood.

Most young children can easily pick up languages and learn immense amounts of knowledge in their early years. How do they pull this off?

Did Alexander Graham Bell really invent the telephone, or did he steal someone else's thunder?

If humans suddenly disappeared and our pets had to fend for themselves, could dogs survive in a world without people?

In case those licks and wagging tail weren't convincing enough, scientists prove what we already know. Our dogs love us. They really, really love us.

You can't watch Earth spin in real time because it rotates so slowly, but there are ways to see the effects of the planet's rotation.

Do mice like eating cheese, or is it a myth?

During the last ice age, which route was taken by the first humans to reach the Americas, and did they travel by foot, boat or both?

Birds do produce urine, but it doesn't come out the same way it does in humans. How birds pee may be an evolutionary adaptation that benefits flight.

Leading theories suggest that the first energy used by life was either from the sun or from geothermal heat and chemistry at the bottom of the ocean.

There are a few strategies for keeping nuclear weapons from accidentally detonating, including where and how the nuclear components are stored.

Most biologists will answer confidently when asked 'which came first, the chicken or the egg?" but the answer may depend on what type of egg you're talking about.