Radioactivity (Radioactive Decay):
The disintegration of unstable heavy atomic nuclei into lighter, more stable, atomic nuclei, accompanied in the process by the emission of ionizing radiation (alpha particles, beta particles orgamma rays). This is a random process at the atomic level but, given a large number of similar atoms, the decay rate on average is predictable, and is usually measured by the half-life of the substance.
Redshift:
The shifting of emitted electromagnetic radiation (such as visible light) towards the less energetic red end of the electromagnetic spectrum when a light source is moving away from the observer. This occurs as the wavelengths of lightstretch as an object moves away (as opposed to being squashed by an approaching object), similar to the familiar Doppler effect on sound waves. Among other things, it can be used as a measure of the speed with which galaxies throughout the universe are moving away from us.
Relativity:
The theory, formulated essentially by Einstein’s theory has two main parts: the Special Theory of Relativity (or special relativity) which deals with objects in uniform motion, and the General Theory of Relativity (or general relativity) which deals with acclerating objects and gravity.
RNA and DNA:
Ribonucleic acid (RNA) is a type of single-stranded moleculethat consists of a long chain of nucleotide units, each of which consists of a nitrogenous base, a ribose sugar and a phosphate. RNA transmits the genetic information from DNAinto the nucleus of cells, and controls certain chemical processes in the cell. Both DNA and RNA are considered essential building blocks of life.
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