The oldest thing ever ...

... was on display this weekend:

A tiny grain of crystal thought to the oldest object on Earth has gone on public display for one day only in the US state of Wisconsin.

The 4.4 billion-year-old zircon crystal, barely two human hairs wide, was brought out at the University of Wisconsin-Madison on Saturday.

The day's festivities also featured the Rock Concert, which was to include jazz from a band using rocks as percussion.

The zircon, found in Australia in 2001, led to a reappraisal of early Earth.

Analytical work by geophysicist Professor John Valley at the university in Madison, Wisconsin, showed the crystal could only have formed in a low-temperature environment.

That suggested the early Earth was much cooler than previously thought, meaning life-forming elements such as oceans were formed earlier too.