An electron in an atom can go from a lower energy level to a higher energy level if the atom

Thermal radiation is defined as

Which of the following statements about comets and asteroids is true?

According to the universal law of gravitation, the force due to gravity is

What evidence leads astronomers to conclude that most of the Milky Way’s mass consists of a mysterious dark matter?

Which law explains why a skater can spin faster by pulling his arms closer to his body, or spin slower by spreading his arms out?

Which person below created a model of the solar system that put the Sun in the center, but that was not very accurate because he assumed that the orbits of the planets must be perfect circles?

Which of the following was the first strong evidence for an asteroid impact being the cause of the extinction of the dinosaurs 65 million years ago (as well as 75% of all species alive at the time)?

What evidence leads astronomers to conclude that most of the Milky Way’s mass consists of a mysterious dark matter?

Gravity follows an inverse square law. This means that if the distance between two masses is decreased by a factor of 4, the gravitational force between those two masses