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A contemporary German popular astronomical book also noticed that light-year is an odd name. [25] In 1868 an English journal labelled the light-year as a unit used by the Germans. [26] Eddington called the light-year an inconvenient and irrelevant unit, which had sometimes crept from popular use into technical investigations. [27]
The first direct measurement of the distance to a star (61 Cygni at 11.4 light-years) was made in 1838 by Friedrich Bessel using the parallax technique. Parallax measurements demonstrated the vast separation of the stars in the heavens. [citation needed] Observation of double stars gained increasing importance during the 19th century. In 1834 ...
The first generation of stars, known as Population III stars, formed within a few hundred million years after the Big Bang. [62] These stars were the first source of visible light in the universe after recombination. Structures may have begun to emerge from around 150 million years, and early galaxies emerged from around 180 to 700 million years.
History is taught as a part of primary and secondary education, and the academic study of history is a major discipline in universities. Herodotus, a 5th-century BCE Greek historian, is often considered the "father of history", as one of the first historians in the Western tradition, [13] though he has been criticized as the "father of lies".
A light-year is the distance light travels in one Julian year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. In round figures, a light year is nearly 10 trillion kilometres or nearly 6 trillion miles. Proxima Centauri, the closest star to Earth after the Sun, is around 4.2 light-years away. [89]
This is the first time that these galaxies have been imaged in such detail, and the first time scientists were able to confirm that they produced enough radiation to end the light-less tyranny of ...
Quantum optics is the study of the nature and effects of light as quantized photons. The first indication that light might be quantized came from Max Planck in 1899 when he correctly modelled blackbody radiation by assuming that the exchange of energy between light and matter only occurred in discrete amounts he called quanta. It was unknown ...
c. 0 seconds (13.799 ± 0.021 Gya): Planck epoch begins: earliest meaningful time. Conjecture dominates discussion about the earliest moments of the universe's history. The Big Bang occurs in which ordinary space and time develop out of a primeval state (possibly a virtual particle or false vacuum) described by a quantum theory of gravity or "Theory of everything".