Gravity

In 1971 both hit the ground at the same time in the near-vacuum, confirming Galileo's insight.

Mass bends the fabric of space and time, and objects follow the curves.

That is why Apollo astronauts could bounce across the surface in bulky suits.

A small magnet can lift a paper clip against the pull of the entire Earth.

It appeared in his Principia and explained both falling apples and planetary orbits.

Despite its immense size, Jupiter only makes up about 0.1% of the solar system's total mass. The Sun's overwhelming mass is what generates its powerful gravitational pull, keeping all planets in orbit.

Earth's gravitational pull isn't uniform across its surface, due to factors like tectonic plate movements and density variations. Areas with higher mass or density exert a slightly stronger pull, creating measurable "gravity anomalies" across the globe.

Rather than empty spaces, black holes are regions in spacetime where gravity is so intense that nothing, not even light, can escape. They form from the remnants of massive stars that collapse under their own gravity, creating a singularity.

Without the constant pull of gravity, the vertebrae in an astronaut's spine are no longer compressed, allowing the discs to expand slightly. This temporary increase in height reverts to normal upon returning to Earth, as gravity reasserts its influence.

According to Einstein's theory of general relativity, gravity causes time to slow down. Since there's slightly less gravitational pull at higher altitudes, time literally ticks faster compared to sea level, a measurable effect of spacetime curvature.