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The Sun is the star at the center of the Solar System.It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light and infrared radiation with 10% at ultraviolet energies.
Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System. Initially, Earth was molten due to extreme volcanism and frequent collisions with other bodies.
The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet. Each eon saw the most significant changes in Earth's composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs.
Earth orbits the Sun, making Earth the third-closest planet to the Sun and part of the inner Solar System. Earth's average orbital distance is about 150 million km (93 million mi), which is the basis for the astronomical unit (AU) and is equal to roughly 8.3 light minutes or 380 times Earth's distance to the Moon .
The ancient Hebrews, like all the ancient peoples of the Near East, believed the sky was a solid dome with the Sun, Moon, planets and stars embedded in it. [4] In biblical cosmology, the firmament is the vast solid dome created by God during his creation of the world to divide the primal sea into upper and lower portions so that the dry land could appear.
The Solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surface.
The luminosity of the Sun increases as it progresses through its life cycle and are visible over the course of millions of years. Sunspots can form on the Sun's surface, which can cause greater variability in the emissions that Earth receives. [15]: 69 Volcanoes form when two plates meet and one subducts underneath the other. [18]
At this average distance, light travels from the Sun to Earth in about 8 minutes, 19 seconds. The energy of this sunlight supports almost all life [b] on Earth by photosynthesis, [13] and drives Earth's climate and weather. [14] As recent as the 19th century, scientists had little knowledge of the Sun's physical composition and source of energy.