Galileo probably never dropped anything off the tower, and did not need to

Everything here earned its place by changing an outcome. Nothing about falling bodies and the leaning tower is included to round the number up.

The story as it is usually told

In the familiar version Galileo climbs the leaning tower, releases two balls of very different weight, and watches them strike the ground together in front of assembled sceptics. The account appears in a life of Galileo written by a pupil who joined him only in his last years and was recording what he had been told. No contemporary account mentions the demonstration, and Galileo, who was not shy about publicising his own results, never described it in print.

The same biography contains several other claims that later scholars have struggled to confirm, which is a reason for caution rather than a verdict of invention. Something of the kind may well have happened, but the evidence is one admiring memoir written long after the man it describes had died.

What the older physics actually claimed

The position Galileo argued against held that a falling body's speed is related to its weight, so that doubling the weight roughly doubles the speed of the fall. This is not a foolish claim, because it describes rather well what happens when you drop a stone and a feather in a room full of air.

Tested properly, ancient physics did not separate the medium from the motion, so resistance was built into the account of falling instead of being treated as interference. Anyone testing the idea with objects light enough for air to matter would have confirmed it, which is a large part of why it lasted so long. The argument was eventually won by isolating the effect of the medium, not by discovering that everyone before had somehow failed to look.

The argument that did the real work

Galileo's published reasoning included a thought experiment: tie a light body to a heavy one and ask whether the pair falls faster or slower than the heavy body alone. On the older view the light body should drag and slow the pair, while the combined weight should also speed it up, and both cannot be true at once.

That contradiction needs no tower, no rope and no audience, and it cannot be dodged by complaining about the accuracy of the measurement. His experimental work used balls rolling down inclined planes, which stretched the motion out over enough time to be measured with the instruments then available. The inclined plane is the genuine experiment in this story, and it is a far cleverer piece of work than a drop lasting under two seconds.

Somebody else did drop the weights

Investigators working in the Low Countries published an account of releasing lead balls of different weights from a height and hearing them land as a single sound. That report appeared in print before the traditional date given for the Pisa demonstration, which makes it the better documented experiment by some distance. Using the ear rather than the eye was a genuinely good choice, because hearing separates two impacts far more sharply than sight separates two landings.

The result was not treated as a revolution at the time, partly because it arrived without the surrounding theory that would have made it matter to anyone. An experiment without a framework tends to be filed and forgotten, and that pattern recurs throughout the history of science.

What happens if you actually try it

Two balls of similar size and different density released together land close enough that the gap is genuinely hard to see from ground level. The denser one arrives fractionally first, because drag depends on size and speed while the resisting force is shared across more mass in the heavier object. Drop a metal ball against a sheet of paper and the older account looks obviously correct, which is precisely the difficulty the argument had to overcome.

Trace it back and inside an evacuated tube everything released together falls together, and demonstrations of that kind settle the matter far more cleanly than any tower could. The modern statement is that acceleration under gravity does not depend on mass in the absence of resistance, and that final clause carries most of the weight.

Printing a correction has a poor record of taking a myth out of circulation.

Why the tower stuck anyway

One dramatic image beats a page of geometry, and the tower supplies a villain, a crowd and a famous leaning landmark in a single picture. It also fits a preferred story about how science works, in which stubborn authority is defeated by a public demonstration rather than by a long argument. The real sequence was slower and more collaborative, involving inclined planes, earlier drop tests abroad and a sustained argument about what a resisting medium does.

Historians who doubt the tower are not doubting the physics, which is about as secure as anything in the subject can be. They are pointing out that the most retold experiment in the story may be the one that never actually took place.

Everything above, in order of what to do first

1. The story as it is usually told. In the familiar version Galileo climbs the leaning tower, releases two balls of very different weight, and watches them strike the ground together in front of assembled sceptics.
2. What the older physics actually claimed. The position Galileo argued against held that a falling body's speed is related to its weight, so that doubling the weight roughly doubles the speed of the fall.
3. The argument that did the real work. Galileo's published reasoning included a thought experiment: tie a light body to a heavy one and ask whether the pair falls faster or slower than the heavy body alone.
4. Somebody else did drop the weights. Investigators working in the Low Countries published an account of releasing lead balls of different weights from a height and hearing them land as a single sound.
5. What happens if you actually try it. Two balls of similar size and different density released together land close enough that the gap is genuinely hard to see from ground level.
6. Why the tower stuck anyway. One dramatic image beats a page of geometry, and the tower supplies a villain, a crowd and a famous leaning landmark in a single picture.

The takeaway

A tower makes a better picture than an inclined plane. The inclined plane is where the thinking actually happened.

The satisfying version of a story is the one that travels, which is the whole problem.