The Earth’s atmosphere is composed of 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and trace amounts of other gases, including water vapor. The atmosphere is a layer of gases that surround the Earth and provide a shield from the Sun’s ultraviolet radiation, which can be damaging to living organisms. The atmosphere also helps to regulate the temperature of the Earth’s surface.

DNA is composed of two strands, each of which is composed of four nitrogenous bases: adenine (A), thymine (T), cytosine (C) and guanine (G). These four bases are linked together by hydrogen bonds and form a double helix. The two strands of the double helix are antiparallel, meaning that they run in opposite directions, with A-T and C-G base-pairing between the two strands.

The speed of light is a fundamental constant of nature, which is 299,792,458 meters per second (approximately 186,282 miles per second). Light moves faster than any other form of electromagnetic radiation, and is the fastest form of energy in the universe. Light is also the basis of all of the fundamental laws of physics, such as Einstein’s Theory of Relativity.