Why do you need a reference point to know that something is moving

Where would you expect to see seedless plants, such as ferns and mosses? a. in a botanical museum, because they are all extinct b. low and close to the ground in a moist environment c. climbing high while circling the branches of another plant d. deeply rooted in a forest with a trunk that reaches 20 meters or more

Each pair of clay balls represents two planetesimals. if each planetesimal is composed of the same material and is separated he the same distance, which pair experiences the frayed gravitational attraction?

Si el equipo no fuera bueno no con el entrenador.