In 1804, the people of Haiti won the Haitian Revolution, and Haiti became an independent country. Port-au-Prince became the capital of this new country. During the French and Haitian Revolutions, it was called "Port-Républicain", before Jean-Jacques Dessalines renamed it Port-au-Prince.
Shortly after it won its independence, Haiti's new leaders divided the country between a kingdom in the north and a republic in the south. Port-au-Prince remained the capital of the republic.
Port-au-Prince is the cultural centre of Haiti. The State University of Haiti ("L'Université d'État d'Haïti," or UEH, in French); the Université Quisqueya; and the "Université Caraïbe" are all located in the city.
Port-au-Prince is the nation's largest centre of economy and finance. It has the most important port in the country, where coffee and sugar are exported. Port-au-Prince has soap, textile, and cement factories, and others to process foods.
There is also an international airport about north of the city. It is named "Aéroport International Toussaint L'ouverture" after national hero Toussaint L'ouverture.
Hamelin
Hameln (English name sometimes "Hamelin") is a city in Germany. In 2005, about 58,000 people lived there. A very well-known story from there is called The Pied Piper of Hamelin ("Der Rattenfänger von Hameln"). The story dates from the Middle Ages.
Mikoyan-Gurevich MiG-25
The MiG-25 Foxbat is a fast fighter plane made made by Russian airplane company Mikoyan. Its primary goal is to attack enemies at high speed and altitude. It first flew in 1964 and was introduced in 1970. In 1976, a Soviet MiG-25 pilot left the Soviet Union and flew his plane to Japan, where it was looked at. It is very fast, and can go Mach 3.2 (3.2 times the speed of sound). However, the engines could be destroyed if the plane is flown this fast. It can carry 4 radar guided missiles and 4 heat seeking missiles. It is now being replaced by the MiG-31 Foxhound, but is used a little in other countries.
Semi-major and semi-minor axes
In geometry, the semi-major axis is the distance from the center of an ellipse to the farthest point on the perimeter of the ellipse. The semi-major axis is half of the major axis, which goes all the way across the ellipse at the widest part. The semi-minor axis is a line segment that is at 90 degrees with the semi-major axis. For the circle, the lengths of the semi-axes are both equal to the radius.
Apsis
In astronomy, an apsis, plural "apsides" (IPA: //) is the point of greatest or least distance of the elliptical orbit of an astronomical object from its center of attraction, which is generally the center of mass of the system.
The point of closest approach is called the periapsis or pericentre and the point of farthest excursion is called the apoapsis (Greek από, "from", which becomes απ before a vowel, and αφ before rough breathing), apocentre or apapsis (the latter term, although etymologically more correct, is much less used). A straight line drawn through the periapsis and apoapsis is the "line of apsides". This is the major axis of the ellipse, the line through the longest part of the ellipse.
Similar words are used to identify the body being orbited. The most common are perigee and apogee, referring to orbits around the Earth, and perihelion and aphelion, referring to orbits around the Sun (Greek ‘ήλιος "hēlios" sun). During the Apollo program, the terms pericynthion and apocynthion were used when referring to the moon.
The perihelion is the point in the orbit of an object that is nearest to the Sun. The aphelion is the point in the orbit of an object where it is farthest from the Sun.
All planets, comets and asteroids in our solar system have approximately elliptical (a kind of non-circular) orbits. Thus, they all have a closest and a farthest point from the sun: a perihelion and an aphelion. Orbital eccentricity measures the flatness of the orbit. Any single revolution of a body around the sun is only approximately elliptical, because the precession of the perihelion prevents the orbit from being a simple closed curve such as an ellipse. This causes Milankovich cycles.
Earth comes closest to the sun every year around January 3. It is farthest from the sun every year around July 4. The difference in distance between Earth's nearest point to the sun in January and farthest point from the sun in July is . Earth is about from the Sun in early January, in contrast to about in early July.
When Earth is closest to the Sun, it is winter in the northern hemisphere and summer in the southern hemisphere. Thus it is possible to see that Earth's distance from the Sun does not noticeably cause the seasons to change; the relatively minor effects of differences in distance is somewhat masked by the mainly oceanic southern hemisphere vs the half-continental northern hemisphere. Therefore, the Earth's seasons come and go mainly because Earth does not rotate with its axis exactly upright with respect to the plane of the Earth’s orbit around the sun. Earth's axial tilt is 23.5 degrees. This puts the Sun farther south in December and January, so the north has winter and the south has summer. Thus winter falls on that part of the globe where sunlight strikes least directly. Summer falls on that part of the globe where sunlight strikes most directly.
Orbital eccentricity
In astrodynamics, orbital eccentricity shows how much the shape of an object's orbit is different from a circle.
Eccentricity (formula_1) is defined for all circular, elliptic, parabolic and hyperbolic orbits. It can take the following values:
Here is a formula to find eccentricity:
formula_6
Where e is the eccentricity, r is the apoapsis (far point) of the object's orbit, and r is the periapsis (near point) of the object's orbit. The near and far points are the apsides.
Astronomical unit
The astronomical unit (AU) is a unit of length derived from the Earth's orbit. It is the average distance the Earth gets from the Sun "on the long axis of the ellipse". Its definition is: the length of the semi-major axis of the Earth's elliptical orbit around the Sun. "Semi-major" means half the long axis.
The AU is about 150 million kilometers or 93 million miles. Astronomers usually measure distances within the Solar System in astronomical units. Mars is about 1.4 AU from the Sun, Jupiter lies at roughly 5.2 AU, and Neptune is roughly 30 AU from the Sun. Light travels an AU in about 8.317 minutes.
From 1976 to 2012 the AU was defined as “the radius of an unperturbed circular Newtonian orbit about the Sun of a particle having infinitesimal mass, moving with a mean motion of 0.01720209895 radians per day (known as the Gaussian constant)”. In 2012, the IAU redefined it to be simply .
In the IERS numerical standards, the speed of light in a vacuum is defined as "c" = , in accordance with the SI units. The time to cover an AU is τ = , resulting in the astronomical unit in metres as "c"τ = . It is very roughly the distance from the Earth to the Sun.
Degree (angle)
In mathematics, a degree is a common way to measure plane angle. It is written with the symbol formula_1, where formula_2 corresponds to the entire circle.
It is not an SI unit. The SI uses radian to measure plane angle. However, according to the SI brochure, it is an accepted unit by SI.
The actual reason of choosing the degree as a way to measure plane angle is unknown. One theory says that it is related with the fact that a year is approximately 360 days. Some ancient calendars, for example the Persian calendar and the Babylonian calendar, used 360 days for a year.
Another theory says that the Babylonians divided the circle using the angle of an equilateral triangle. The angle was then divided into 60 parts. This is because they used sexagesimal or base-60 numeral system.
Epoch (astronomy)
In astronomy, an epoch (or sometimes epochal moment) is a moment in time for which the position or the orbital elements of a celestial body are specified.