The word “planet” comes from the Greek word for “wanderer.” Ancient astronomers defined planets as objects that moved in the night sky against a background of fixed stars. Today, astronomers define a planet as an object in orbit around the Sun that is large enough (massive enough) to have its self-gravity pull itself into a round, or nearly round, shape.
In addition, a planet orbits in a clear path around the Sun—there are no other bodies in its path that it must “sweep up” (or clear) as it moves around the Sun.
Camels are the only animals with humps. A camel’s hump is a giant mound of fat, Which can weigh as much as 80 pounds (35 kilograms). The hump allows a camel to survive up to two weeks without food. Because camels typically live in the deserts of Africa and the Middle East, where food can be scarce for long stretches, their hump is key to their survival. When camels are born their humps are empty pockets of flexible skin. As a camel grows and begins to form its fatty tissue reserves, the humps begin to fill out and take shape.
The humps also come in handy for humans who have domesticated the camel. For thousands of years, people have used these strong, resilient creatures for transportation and for hauling goods. The two-hump, or Bactrian, camel was domesticated sometime before 2500 B.C.E., probably in northern Iran, northeastern Afghan – istan, and northern Pakistan. The one-hump, or Dromedary, camel was domesticated sometime between 4000 and 2000 B.C.E. in Arabia.