The project title is “Bending Spacetime in the Basement,” and remarkably, the page does eventually deliver on it.
Visit Bending Spacetime in the Basement
Fourmilab’s experiment starts with a problem that is easy to state and difficult to feel: every object with mass attracts every other object with gravity, yet two ordinary objects sitting near each other do not visibly lunge together.
Gravity is simply too weak compared with electromagnetic forces.
The page turns that weakness into a basement experiment.
Cavendish without the laboratory budget
The core instrument is a torsion balance, a simplified descendant of the apparatus Henry Cavendish used in 1798 to measure gravitational effects.
Instead of attempting precision metrology, the Fourmilab project aims at something more approachable: make the attraction between human-scale masses visible at all.
The article walks through Newtonian gravitation, the gravitational constant, comparisons between gravity and electromagnetism, differential measurement and the reason a torsion balance can cancel the overwhelming constant pull of Earth while remaining sensitive to much smaller changes from nearby masses.
It even includes interactive calculations for gravitational force and translates tiny forces into more imaginable equivalents.
The tone is part of why the page survives as good web writing. It is technically serious without pretending experiments are sacred rituals available only to institutions. The opening joke is about finally being old enough to go into the basement and bend spacetime without somebody calling Mom.
That combination matters.
A textbook can present the formula. Fourmilab tries to make the formula physically annoying enough that you build something.
The page also quietly demonstrates an old-web strength: one author can move from history to equations to apparatus design to jokes without waiting for a content strategy meeting.
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The experiment is not a substitute for a precision laboratory. It is better in another way: it makes universal gravitation feel like something happening between objects you can touch.