Why do planets orbit the Sun?
Quick Answer
The Sun’s gravity constantly pulls planets inward while their sideways motion keeps them from falling in.
The Full Story
The Sun contains about 99.8 percent of the mass in the solar system, so its gravity dominates. Planets formed from a spinning disc of gas and dust around 4.6 billion years ago, inheriting sideways motion. Gravity bends that straight-line motion into a curved path, and the balance between speed and gravity produces an orbit. Isaac Newton explained this in 1687, and Einstein later described gravity as the curving of spacetime by mass. Closer planets must move faster to stay in orbit: Mercury travels about 47 kilometres per second, while Earth moves about 30 kilometres per second.
Key Facts
YouTube Angle
Suggested video title for this topic:
"Earth is always falling toward the Sun — and always missing"