
112
MELTING POINT
BOILING POINT
DENSITY
Tick tock. The atomic clock that controls the
NHK time broadcasts* works by monitoring
the energy fluctuations of a rubidium isotope
and misses by only 1 second every 10 years
or so. The half-life of rubidium is a whopping
48.8 billion years, perfect for assessing the
age of Earth’s minerals and asteroid rem-
nants. This is done by measuring the rubid-
ium left in the sample, then calculating how
long it took ...