The Moon That Rang Like a Bell
When a spent spacecraft was crashed into the Moon, its surface kept trembling for almost an hour.
What was reported
Apollo 12 left a seismometer on the Moon's Ocean of Storms in November 1969. After the astronauts returned to their command module, the empty upper stage of their lunar module was deliberately crashed into the surface about 75 km away, to make a moonquake that scientists could measure.
On Earth, a crash like that would set the ground shaking for a minute or so. On the Moon, the vibrations built up slowly and went on for nearly an hour. Scientists said the Moon had 'rung like a bell', and the phrase was soon taken as a sign that the Moon was hollow.
Explanations offered
Seismologists explain that the Moon's crust is extremely dry and shattered by billions of years of impacts. Without water to absorb them, seismic waves bounce and scatter through the broken rock for a long time, rather than dying away. Later impacts and moonquakes behaved the same way. The Moon isn't hollow; its mass and seismic data show a dense core.
- When
- 20 November 1969
- Where
- Ocean of Storms, the Moon (Apollo 12 landing site)
- Witnesses
- Scientists reading Apollo 12's seismometer
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.