How can smoking marijuana affect your health?

How do we know the earth is round? Why do some people make noises during sex? Why do crabs move sideways? Why are some parts of the sea violent with lots of waves, whereas others aren't? How can smoking marijuana affect your health? How can some female bees reproduce without males? What causes motion sickness? And why do some females grow facial hair? Plus, scientists in Australia have uncovered evidence of the earliest animal...