Compound matrix: Difference between revisions
en>Michael Hardy |
en>Mild Bill Hiccup layout |
||
| Line 1: | Line 1: | ||
'''Jacques Laskar''' (born 28 April 1955 in [[Paris]]) is a French [[astronomy|astronomer]]. He is a research director at the [[French National Centre for Scientific Research]] (CNRS), and a member of ''Astronomy and dynamical systems'' of the [[Institute of Celestial Mechanics and Computing Ephemerides]] (IMCCE) of the [[Paris Observatory]]. He received the [[CNRS Silver medal]] in 1994. Since 2003, he is a member of the [[French Academy of Sciences]].<ref>[http://www.academie-sciences.fr/academie/membre/Laskar_Jacques.htm Member bio] at French Academy of Sciences</ref> | |||
== Teaching career == | |||
After graduation, Laskar taught high school and colleges from 1977 to 1980 at the [[École Normale Supérieure de Cachan]]. Then, he taught aggregation mathematics in 1981 and a year later, he taught astronomy and celestial mechanics. He then joined [[Bureau des Longitudes]] as a research officer second class of CNRS in 1985. | |||
==Research work == | |||
===Stability of the Solar System === | |||
In 1989, Laskar provided evidence that the Solar System is [[Chaos Theory|chaotic]] instead of [[Quasiperiodicity|quasi-periodic]] as originally determined by [[Laplace]] and [[Lagrange]].<ref>{{cite journal |last=Laskar |first=Jacques |year=1989 |title=A numerical experiment on the chaotic behaviour of the Solar System |journal=Nature |volume=338 |pages=237-238 |doi=10.1038/338237a0}}</ref> More specifically, his estimate of the maximum [[Lyapunov exponent]] measuring the exponential divergence of two nearby orbits is <math>1/5 \; \text{Myr}^{-1}</math>, meaning that it is possible to predict the trajectories of the Solar System over 10 Myr but fundamentally impossible over more than 100 Myr. This chaoticity comes mainly from the inner planets [[Mercury (planet)|Mercury]], [[Venus]] the [[Earth]] and [[Mars]]. | |||
In 2009, he and his colleague Mickeal Gastineau generated numeric simulations of orbital instability over the next five billion years. Unlike previous models, they took into account Albert Einstein's theory of general relativity. Over a short time span, this made little difference, but over the long haul it resulted in dramatically different orbital paths. The researchers looked at 2501 possible scenarios, 25 of which ended with a severely disrupted solar system.<ref>http://www.news.com.au/earth-venus-smash-up-possible/story-0-1225732704812</ref> | |||
=== Chaotic obliquity of the planets === | |||
Laskar also contributed to the study of the evolution of the skew planets of the solar system. One can for example include his work on [[retrograde motion|retrograde rotation]] of Venus.<ref>http://www.newscientist.com/article/dn879-back-flip.html</ref> With his colleague Alexandre Correla, at Astronomie et Systemes Dynamiques of Paris, he found out that the atmosphere may simply have slowed the planet down and then started it spinning the other way. This insidious process would have been the unique result of the thick atmosphere always lagging behind as the planet rotates. | |||
===Paleoclimates === | |||
He has contributed to the [[astronomical theory of paleoclimates]], studying the orbits of the planets and the obliquity of the solar system allowing it to link with the study of climate on geological time scales <ref>[http://www.imcce.fr/Equipes/ASD/person/Laskar/jxl_insola.html Astronomical study of paleoclimate Earth and Mars]</ref> | |||
==See also== | |||
* [[Celestial mechanics]] | |||
* [[Chaos Theory]] | |||
* [[Milankovitch cycles]] | |||
* [[Stability of the Solar System]] | |||
==References== | |||
{{Reflist}} | |||
==External links== | |||
* [http://www.imcce.fr/Equipes/ASD/person/Laskar/Laskar.html Jacques Laskar's home page] on the site of the IMCCE | |||
{{Persondata | |||
| NAME = Laskar, Jacques | |||
| ALTERNATIVE NAMES = | |||
| SHORT DESCRIPTION = Astronomer | |||
| DATE OF BIRTH = 28 April 1955 | |||
| PLACE OF BIRTH = Paris, France | |||
| DATE OF DEATH = | |||
| PLACE OF DEATH = | |||
}} | |||
{{DEFAULTSORT:Laskar, Jacques}} | |||
[[Category:French astronomers]] | |||
[[Category:Members of the French Academy of Sciences]] | |||
[[Category:1955 births]] | |||
[[Category:Living people]] | |||
[[Category:Scientists from Paris]] | |||
Revision as of 21:42, 9 June 2013
Jacques Laskar (born 28 April 1955 in Paris) is a French astronomer. He is a research director at the French National Centre for Scientific Research (CNRS), and a member of Astronomy and dynamical systems of the Institute of Celestial Mechanics and Computing Ephemerides (IMCCE) of the Paris Observatory. He received the CNRS Silver medal in 1994. Since 2003, he is a member of the French Academy of Sciences.[1]
Teaching career
After graduation, Laskar taught high school and colleges from 1977 to 1980 at the École Normale Supérieure de Cachan. Then, he taught aggregation mathematics in 1981 and a year later, he taught astronomy and celestial mechanics. He then joined Bureau des Longitudes as a research officer second class of CNRS in 1985.
Research work
Stability of the Solar System
In 1989, Laskar provided evidence that the Solar System is chaotic instead of quasi-periodic as originally determined by Laplace and Lagrange.[2] More specifically, his estimate of the maximum Lyapunov exponent measuring the exponential divergence of two nearby orbits is , meaning that it is possible to predict the trajectories of the Solar System over 10 Myr but fundamentally impossible over more than 100 Myr. This chaoticity comes mainly from the inner planets Mercury, Venus the Earth and Mars.
In 2009, he and his colleague Mickeal Gastineau generated numeric simulations of orbital instability over the next five billion years. Unlike previous models, they took into account Albert Einstein's theory of general relativity. Over a short time span, this made little difference, but over the long haul it resulted in dramatically different orbital paths. The researchers looked at 2501 possible scenarios, 25 of which ended with a severely disrupted solar system.[3]
Chaotic obliquity of the planets
Laskar also contributed to the study of the evolution of the skew planets of the solar system. One can for example include his work on retrograde rotation of Venus.[4] With his colleague Alexandre Correla, at Astronomie et Systemes Dynamiques of Paris, he found out that the atmosphere may simply have slowed the planet down and then started it spinning the other way. This insidious process would have been the unique result of the thick atmosphere always lagging behind as the planet rotates.
Paleoclimates
He has contributed to the astronomical theory of paleoclimates, studying the orbits of the planets and the obliquity of the solar system allowing it to link with the study of climate on geological time scales [5]
See also
References
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
External links
- Jacques Laskar's home page on the site of the IMCCE
- ↑ Member bio at French Academy of Sciences
- ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ http://www.news.com.au/earth-venus-smash-up-possible/story-0-1225732704812
- ↑ http://www.newscientist.com/article/dn879-back-flip.html
- ↑ Astronomical study of paleoclimate Earth and Mars