In physics, a redshift is an increase in the wavelength, or equivalently, a decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and energy, is known as a blueshift. The terms are derive from the colours red and blue, which form the extremes of the visible-light spectrum. Three forms of redshift occur in astronomy and cosmology: Doppler redshifts due to the relative motions of radiation sources, gravitational redshift as radiation escapes from gravitational potentials, and cosmological redshifts caused by the universe expanding. Automated astronomical redshift surveys are an important tool for learning about the large scale structure of the universe. Examples of strong redshifting are a gamma ray perceived as an X-ray, or initially visible light perceived as radio waves. The initial heat from the Big Bang has redshifted far down to become the cosmic microwave background.
Read more: <https://en.wikipedia.org/wiki/Redshift> _______________________________ Today's selected anniversaries: 1934: Jeannette Piccard piloted a hot-air balloon flight that reached 57,579 feet (17,550 m), becoming the first woman to fly in the stratosphere. <https://en.wikipedia.org/wiki/Jeannette_Piccard> 1957: A screening of Mother India, one of the most influential Indian films in history, was held for President Rajendra Prasad and Prime Minister Jawaharlal Nehru two days before its release. <https://en.wikipedia.org/wiki/Mother_India> 1995: The runway show for Alexander McQueen's collection The Hunger was staged at London's Natural History Museum. <https://en.wikipedia.org/wiki/The_Hunger_%28collection%29> 2018: An escalator accident in Rome left 24 people injured, mostly fans of the CSKA Moscow football team who were in town for a UEFA Champions League match against Roma. <https://en.wikipedia.org/wiki/2018_Rome_escalator_accident> _____________________________ Wiktionary's word of the day: entreat: 1. Senses relating to asking or pleading. 2. (transitive) To ask earnestly or beg for (something, such as a benefit or favour). 3. (transitive) To earnestly ask or beg (someone); to beseech, to implore. 4. (transitive, obsolete) To try to influence or persuade (someone); to induce, to prevail upon. 5. (intransitive) Often followed by for: to ask earnestly or to beg for a benefit, favour, etc.; to appeal, to plead. 6. (intransitive, archaic) To make a petition or request on behalf of someone; to intercede, to plead. 7. (obsolete) Senses relating to dealing with or negotiating. 8. (transitive) To act towards or deal with (someone or something) in a specified manner; to handle, to treat. 9. (transitive) To discuss or negotiate (something); also, to discuss or negotiate with (someone). 10. (transitive, reflexive) To occupy oneself with (something). 11. (intransitive) Sometimes followed by of or upon: to give an account or description of a matter; to deal with. 12. (intransitive) Often followed by about, for, or of: to discuss or negotiate, especially in order to reach a settlement. 13. (obsolete) Synonym of entreaty (“an act of asking earnestly or begging for something”); an appeal, a plea. <https://en.wiktionary.org/wiki/entreat> ___________________________ Wikiquote quote of the day: Historians may lie, but History cannot. --George Saintsbury <https://en.wikiquote.org/wiki/George_Saintsbury> _______________________________________________ Wikipedia Daily Article mailing list. To unsubscribe write to: [email protected] Questions or comments? Contact [email protected]
