The most energetic objects, events, and processes in the universe give off x-rays and gamma rays.
Newton pointed out that you can calculate the force of gravity between two objects if you know their mass and their distance apart.
Dark energy acts opposite gravity and continues to speed up universal expansion today.
The nearest stars are about 4.2 light-years from the Sun.
The Milky Way is moving through space at an estimated velocity of 630 kilometers per second.
Light can act as a particle, called a photon, or it can travel through space as a wave.