A day on Earth is supposed to be exactly 86,400 seconds. But precise measurements show that Earth’s rotation speed changes ...

At half the size of Earth and one-tenth its mass, Mars is a featherweight as far as planets go. Yet new research reveals the ...

Curious Kids is a series for children of all ages. If you have a question you'd like an expert to answer, send it to ...

Which way is ‘down’ has a different answer depending on where you are on Earth, in the solar system, in our galaxy and beyond ...

The space rock, known as "2026 AJ" and 40 feet in diameter, is hurtling toward our planet at around 20,500 miles per hour.

This video explains how motion, inertia, and Earth’s rotation affect a jump inside an aircraft, and why you land in the same ...