How do you study things you cannot see

For things that we can not directly observe, we can use indirect observation – which studies the consequences of an action or process. For example, we cannot see the Earth's magnetic field, but we detect it by its effect on a compass.

i don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.

all eukaryotic cell have mitochondria : )