A Way to remember the Entire Unit Circle for Trigonometry
La gravitation universelle, cours de physique de seconde, 2d06ph
Pour aller plus loin : I- Le mouvement de la Lune. 1)- Le mouvement de la Lune pour un observateur terrestre. - Pour un observateur terrestre, la Lune se lève à Est et se couche à l’Ouest. - La trajectoire de la Lune dans le ciel change d’un jour à l’autre. - Le mouvement de la Lune par rapport à la Terre est complexe. - Le référentiel terrestre n’est pas adapté pour l’étude du mouvement de la Lune. - On préfère utiliser le référentiel Géocentrique. 2)- Le référentiel Géocentrique. - Le référentiel Géocentrique est un solide constitué par le centre de la Terre et des étoiles lointaines dont les positions n’ont pas varié depuis des siècles. - Le référentiel Géocentrique n’est par entraîné dans le mouvement de rotation de la Terre. - Le principe de l’inertie s’applique dans le référentiel Géocentrique. - Animation 3)- Trajectoire de la Lune. - Dans le référentiel Géocentrique, la trajectoire de la Lune est pratiquement un cercle de rayon R = 384 000 km. - Soit 60 fois le rayon de la Terre. - Énoncé :
Cosmology
The Hubble eXtreme Deep Field (XDF) was completed in September 2012 and shows the farthest galaxies ever photographed by humans. Except for the few stars in the foreground (which are bright and easily recognizable because only they have diffraction spikes), every speck of light in the photo is an individual galaxy, some of them as old as 13.2 billion years; the observable universe is estimated to contain more than 200 billion galaxies. Cosmology (from the Greek κόσμος, kosmos "world" and -λογία, -logia "study of"), is the study of the origin, evolution, and eventual fate of the universe. Physical cosmology is the scholarly and scientific study of the origin, evolution, large-scale structures and dynamics, and ultimate fate of the universe, as well as the scientific laws that govern these realities.[1] Religious cosmology (or mythological cosmology) is a body of beliefs based on the historical, mythological, religious, and esoteric literature and traditions of creation and eschatology.
Newton's laws of motion
First law: When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force.[2][3]Second law: F = ma. The vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration vector a of the object.Third law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body. The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687.[4] Newton used them to explain and investigate the motion of many physical objects and systems.[5] For example, in the third volume of the text, Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler's laws of planetary motion. Overview Newton's first law Impulse
Loi universelle de la gravitation
Un article de Wikipédia, l'encyclopédie libre. Les satellites et les projectiles obéissent à la même loi. Expression mathématique selon Isaac Newton[modifier | modifier le code] Deux corps ponctuels de masses respectives et s'attirent avec des forces de mêmes valeurs (mais vectoriellement opposées), proportionnelles à chacune des masses, et inversement proportionnelle au carré de la distance qui les sépare. La force exercée sur le corps par le corps est vectoriellement donnée par en kilogramme (kg); d en mètre (m); en newton (N) où G est la constante gravitationnelle, elle vaut dans les unités SI, le CODATA 2010 [2] Énergie potentielle de gravitation[modifier | modifier le code] Voici le calcul menant à l'expression de l'énergie potentielle de gravitation d'un corps de masse m à une distance R d'un corps de masse M produisant le champ de gravitation : D'où : Énergie potentielle d'une sphère homogène[modifier | modifier le code] Soit un corps sphérique de rayon R et de masse volumique uniforme , on a :
Introduction to general relativity
High-precision test of general relativity by the Cassini space probe (artist's impression): radio signals sent between the Earth and the probe (green wave) are delayed by the warping of spacetime (blue lines) due to the Sun's mass. General relativity is a theory of gravitation that was developed by Albert Einstein between 1907 and 1915. According to general relativity, the observed gravitational effect between masses results from their warping of spacetime. By the beginning of the 20th century, Newton's law of universal gravitation had been accepted for more than two hundred years as a valid description of the gravitational force between masses. In Newton's model, gravity is the result of an attractive force between massive objects. General relativity has developed into an essential tool in modern astrophysics. Although general relativity is not the only relativistic theory of gravity, it is the simplest such theory that is consistent with the experimental data. Tidal effects[edit]
Infinite [Internet Encyclopedia of Philosophy]
Working with the infinite is tricky business. Zeno’s paradoxes first alerted philosophers to this in 450 B.C.E. when he argued that a fast runner such as Achilles has an infinite number of places to reach during the pursuit of a slower runner. Since then, there has been a struggle to understand how to use the notion of infinity in a coherent manner. This article concerns the significant and controversial role that the concepts of infinity and the infinite play in the disciplines of philosophy, physical science, and mathematics. Philosophers want to know whether there is more than one coherent concept of infinity; which entities and properties are infinitely large, infinitely small, infinitely divisible, and infinitely numerous; and what arguments can justify answers one way or the other. Here are four suggested examples of these different ways to be infinite. This article also explores a variety of other questions about the infinite. Table of Contents 1. a. b. How big is infinity?
History of Cosmology
Cosmology is the study of the Universe and its components, how it formed, how its has evolved and what is its future. Modern cosmology grew from ideas before recorded history. Ancient man asked questions such as "What's going on around me?" To religious studies, cosmology is about a theistically created world ruled by supernatural forces. Many of the earliest recorded scientific observations were about cosmology, and pursue of understanding has continued for over 5000 years. Modern cosmology is on the borderland between science and philosophy, close to philosophy because it asks fundamental questions about the Universe, close to science since it looks for answers in the form of empirical understanding by observation and rational explanation. Neolithic Cosmology: Cosmology is as old as humankind. The earliest physical evidence of astronomical and cosmological thinking is a lunar calendar found on a bone fragment in Sub-Saharan Africa dated at about 20,000 BC. Greek Cosmology:
