Formation and evolution of the Solar System

The formation and evolution of the Solar System began 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the centre, forming the Sun, while the rest flattened into a protoplanetary disc out of which the planets,moons, asteroids and othersmall Solar System bodies formed.

This widely accepted model, known as the nebular hypothesis, was first developed in the 18th century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace. Its subsequent development has interwoven a variety of scientific disciplines including astronomy, physics, geology, and planetary science. Since the dawn of the space age in the 1950s and the discovery of extrasolar planets in the 1990s, the models have been both challenged and refined to account for new observations.

The Solar System has evolved considerably since its initial formation. Many moons have formed from circling discs of gas and dust around their parent planets, while many other moons are believed to have been bodies captured by their planets or, as in the case of the Earth's Moon, to have resulted from . Collisions between bodies have occurred continually up to the present day and are central to the evolution of the system. The positions of the planets often shifted, and planets have switched places. This planetary migration is now believed to have been responsible for much of the Solar System's early evolution.

Just as the Solar System formed, so it will eventually disintegrate. In roughly 5 billion years, the Sun will cool and expand outward to many times its current diameter (becoming a red giant) before casting off its outer layers as a planetary nebula and leaving behind a stellar corpse known as a white dwarf. The planets will follow the Sun's course; in the far distant future, the gravity of passing stars will gradually whittle away at the Sun's retinue of planets. Some will be destroyed, others ejected into interstellar space. Ultimately, over the course of trillions of years, the Sun will likely be left alone with no other bodies in orbit.

I was bored because I don't have anything to do at home!! haha!!



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Reference: www.wikipedia.org

The American Map

This is the American Map it has 50 states and is considered the 2nd largest continent in the world.

The United States of America is a constitutional federal republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to its east and Russia to the west across the Bering Strait, and the state of Hawaii is an archipelago in the mid-Pacific. The United States also possesses several territories, or insular areas, scattered around the Caribbean and Pacific.

At 3.79 million square miles (9.83 million km²) and with more than 300 million people, the United States is the third or fourth largest country by total area, and third largest by land area and by population. The United States is one of the world's most ethnically diverse nations, the product of large-scale immigration from many countries.^[7] The U.S. economy is the largest national economy in the world, with a nominal 2006 gross domestic product (GDP) of more than US$13 trillion (over 19% of the world total based on purchasing power parity).^[4][8]

The nation was founded by thirteen colonies of Great Britain located along the Atlantic seaboard. Proclaiming themselves "states," they issued the Declaration of Independence on July 4, 1776. The rebellious states defeated Great Britain in the American Revolutionary War, the first successful colonial war of independence.^[9] A federal convention adopted the current United States Constitution on September 17, 1787; its ratification the following year made the states part of a single republic. The Bill of Rights, comprising ten constitutional amendments, was ratified in 1791.

In the nineteenth century, the United States acquired land from France, Spain, the United Kingdom, Mexico, and Russia, and annexed the Republic of Texas and the Republic of Hawaii. Disputes between the agrarian South and industrial North over states' rights and the expansion of the institution of slavery provoked the American Civil War of the 1860s. The North's victory prevented a permanent split of the country and led to the end of slavery in the United States. The Spanish-American War and World War I confirmed the nation's status as a military power. In 1945, the United States emerged from World War II as the first country with nuclear weapons, a permanent member of the United Nations Security Council, and a founding member of NATO. In the post–Cold War era, the United States is the only remaining superpower—accounting for approximately 50% of global military spending—and a dominant economic, political, and cultural force in the world.


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