The International Astronomical Union defines a planet as a celestial body that orbits the sun, is massive enough that gravity has forced it into a spherical shape, and has cleared away other objects ...

For 76 years, Pluto was the beloved ninth planet. No one cared that it was the runt of the solar system, with a moon, Charon, half its size. No one minded that it had a tilted, eccentric orbit. Pluto ...

A scientific theory is a structured explanation to explain a group of facts or phenomena in the natural world that often incorporates a scientific hypothesis and scientific laws. The scientific ...

In 2008, the National Academy of Sciences put forth a textbook-ish definition of "science": "The use of evidence to construct testable explanations and predictions of natural phenomena, as well as the ...