American scientists, like scientists all over the world, use kilometers (km) instead of miles for measuring distances.

This is because:

* The metric system is the standard system of measurement used in science. The metric system (also known as the International System of Units or SI) is based on powers of 10, making conversions and calculations much simpler.

* Kilometers are the standard unit for measuring distance in the metric system.

* Using a universal system of measurement promotes collaboration and standardization in scientific research. It allows scientists from different countries to easily share data and compare results without having to convert between different units.

While the United States is one of the few countries that still uses the imperial system (including miles), the scientific community globally uses the metric system.