Portal do Professor - The Expanding Universe

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The Expanding Universe

15/12/2008

Ficha Técnica

Estrutura curricular

Educação de Jovens e Adultos - 2º ciclo::Ciências Naturais::Visões de mundo

Educação Básica::Ensino Médio::Física::Universo, terra e vida

Objetivo

The pupil visualizes and understands the expansion of the universe

Descrição

In the 1920s, American astronomer Edwin Hubble discovered that the universe is expanding. Not only are distant stars and galaxies moving away from us, but further stars and galaxies move away from us faster than closer ones. This is because of the homogeneous nature of the expansion. Every distance in the universe expands by the same multiplicative factor, and so an object that is twice as far from us moves twice as far in a given time. Our modern understanding of cosmology is based on Einstein's general theory of relativity. Shortly after the big bang, the universe underwent an inflationary epoch in which the universe expanded exponentially. After the inflationary epoch is complete, basic principles of general relativity tell us that there are three broad types of possible "expansions" of the universe. Loosely speaking, an open universe is one which continues to expand forever, and whose expansion never comes to a halt. A flat universe is one which continues to expand forever, but whose expansion is constantly slowing down. A closed universe eventually stops expanding and then starts contracting until the universe ends in a "big crunch"-the opposite of the big bang. For many years, physicists and astronomers could not tell from observation in which of these three broad types of universe we live, but recent observations of supernovas have given us sufficiently precise information on motion that we now know that we live in an open universe. (The open universe simulated in this Demonstration is only one of many possible types, however, and is not a perfect simulation of ours.)