# Proof Narrative: Heavier objects fall faster than lighter objects even in a perfect vacuum.

## Verdict

**Verdict: DISPROVED**

This one has a clear answer backed by centuries of physics and a live experiment on the Moon: in a vacuum, a feather and a hammer fall at exactly the same rate.

## What was claimed?

The claim is that heavier objects fall faster than lighter ones — even when you remove air entirely from the picture. This idea feels intuitive: a bowling ball seems like it should plummet while a feather floats down. But that intuition is shaped by everyday life in air, not by the underlying physics. The question here is what actually happens when air resistance plays no role at all.

## What did we find?

The math settles this before we even consult any sources. Newton's Second Law says that force equals mass times acceleration, and the gravitational force on an object is its mass times the gravitational constant g. Plug those together and the mass cancels out completely — every object, regardless of how heavy it is, accelerates at exactly g. This isn't an approximation; it's an algebraic identity.

NASA's Glenn Research Center confirms this directly: "all objects, regardless of size or shape or weight, free fall with the same acceleration." That's from their educational resources on aeronautics, published by a government research institution.

The most vivid demonstration came from the Moon in 1971. Apollo 15 Commander David Scott dropped a 1.32 kg hammer and a 0.03 kg feather simultaneously on the lunar surface — essentially a perfect vacuum. They hit the ground at the same time. NASA's own documentation of the mission records that "there was no air resistance and the feather fell at the same rate as the hammer." This is a controlled experiment performed in space, not a thought experiment.

Physics also has a formal principle for this. The Weak Equivalence Principle, a foundation of Einstein's general relativity, states that in a gravitational field the acceleration of any particle is independent of its properties, including its mass. This holds across all tested scales of physics.

The search for counter-evidence turned up nothing credible. Every major physics reference consulted — including NASA, Britannica, and university science resources — agrees unanimously.

## What should you keep in mind?

There is one subtle wrinkle worth knowing: technically, a more massive object pulls the Earth toward it slightly more than a lighter object does. In the two-body problem, both objects are attracted to each other, so the Earth accelerates fractionally more toward a heavy object. But this difference is around 10⁻²⁵ — so far below any measurable threshold that it has no practical meaning and doesn't contradict the principle.

The intuition that heavier objects fall faster isn't random. It comes from real observations in air. Aristotle argued this around 350 BCE based on watching objects fall in the real world, where air resistance does slow down lighter objects. His observation was accurate for everyday conditions — just not for the underlying physics. The claim being evaluated here specifies "a perfect vacuum," which removes air resistance entirely and makes the intuition wrong.

## How was this verified?

This proof combined a symbolic mathematical derivation using Newton's laws with direct verification of three independent sources from NASA and Wikipedia. Full details of the evidence, citations, and source credibility assessments are in [the structured proof report](proof.md) and [the full verification audit](proof_audit.md). You can also [re-run the proof yourself](proof.py) to reproduce every step.