gravity

How torsion balances, the Apollo 15 feather drop, and the MICROSCOPE satellite tested whether all matter falls alike, now to a few parts per quadrillion.

Time moves slower near gravity because mass curves spacetime, and general relativity says clocks deeper in that curvature tick at a measurably slower rate.

Henry Cavendish measured Earth's density in 1798 using a torsion balance. Learn the apparatus, the G mystery, and why gravity's constant is still poorly known today.

Isaac Newton's biography, laws of motion, optics, and verified quirks: needle behind the eyeball, alchemy obsessions, plagiarism wars, and a life of deliberate solitude.

Gravity explained: Newton's universal law, Einstein's curved spacetime, gravitational waves, and why GPS satellites must correct for it.

What causes ocean tides? The Moon's differential gravity, why there are two high tides daily, spring and neap tides, and tidal locking — explained.

Einstein's special and general relativity explained simply: time dilation, E=mc², curved spacetime, gravitational waves, and tests that confirm them.

What if gravity vanished for one second? The math shows orbits shift by millimeters to meters, and the ground may carry you along. A thought experiment.

If the Sun vanished right now, we'd have 8 minutes of sunlight left. Then darkness, plummeting temperatures, and Earth drifting into interstellar space.

What would actually happen if gravity suddenly doubled? Your skeleton would fracture under your own weight, the atmosphere would compress into a dense killing fog, and tall buildings would collapse. But life could still evolve — just very differently.

What would actually happen if Earth suddenly doubled in size? Surface gravity would crush most life, the atmosphere would thicken into a lethal blanket, and reaching space might become impossible.