The combined energy of the two emitted photons is equal to that of the absorbed photon. The speeds of the two emitted photons are less than that of the absorbed photon. The two emitted photons have higher frequencies than the absorbed photon. After sunset, we have about half an hour of twilight. The planets move in elliptical orbits with the Sun at the center of the ellipse.
Inferior planets take more time to go around the Sun than superior planets.
The planets appear to move in the sky through the constellations of the zodiac. There is a large cloud of cold gas between us and the star zeta Ophiucus. We all know that astronauts experience weightlessness in space. We know that hydrogen absorbs photons at a wavelength of 6563 A . Altair must be rotating.