Fusion is a nuclear reaction in which two or more nuclei, the centers of atoms, are forced together and combine creating a new larger atom. This reaction gives off a tremendous amount of energy, usually as light and solar radiation

Even white light from the Sun, which seems like an uninterrupted continuum of wavelengths, has gaps in some wavelengths. The gaps correspond to elements present in the Earth’s atmosphere that act as filters for specific wavelengths

Spectroscopy confirms that hydrogen makes up about 74% of all matter in the universe.