The ratio of $\frac { {}^{14}\mathrm { C } } { {}^{12}\mathrm { C } }$ in a piece of wood is $\frac { 1 } { 8 }$ part that of atmosphere. If half life of ${}^{ 14 } \mathrm { C }$ is 5730 years, the age of wood sample is $\_\_\_\_$ years.
The ratio of $\frac { {}^{14}\mathrm { C } } { {}^{12}\mathrm { C } }$ in a piece of wood is $\frac { 1 } { 8 }$ part that of atmosphere. If half life of ${}^{ 14 } \mathrm { C }$ is 5730 years, the age of wood sample is $\_\_\_\_$ years.