For decades, the four known forces of nature, gravity, electromagnetism, and the strong and weak nuclear forces, have ...

Illustration comparing the planets of the Solar System and the Sun on the same scale. The planets are shown to scale relative to each other but their distances are not. From left to right the bodies ...

Planetary scientists have long debated where the material that formed Earth comes from. Despite its location in the inner solar system, they consider it likely that 6–40% of this material must have ...