Final answer:
The correlation coefficient between two variables is unchanged by different units of measurement; hence, the correlation between the heights of male gnu and their adult offspring will remain 0.87 even if measured in lightyears and millimeters.
Step-by-step explanation:
The correlation coefficient is a measure of the linear relationship between two variables, which is independent of the units of measurement. This means that the correlation coefficient remains the same regardless of the units used to measure the variables. Given that the correlation between the heights of male gnu and their adult offspring is r = 0.87, this value will not change even if the heights of the male gnu are measured in lightyears and their adult offspring in millimeters. Therefore, the correlation of heights after changing the units of measurement will still be 0.87.