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sexta-feira, 26 de abril de 2013

Einstein Proved Right on Gravit, Again - Gautam Naik (WSJ)

Parece que Einstein fez uma aposta com Deus; por enquanto está acertando...
Mas, segundo o paradigma de Karl Popper, em algum momento vai ser desmentido, não por Deus, mas por outros cientistas...
Paulo Roberto de Almeida

Einstein Proved Right on Gravit, Again

The Wall Street Journal, April 26, 2013, page A3

Scientists have subjected Albert Einstein's famous theory of gravity to its toughest real-world test so far—and it has prevailed.
The theory, which was published nearly a century ago, had already passed every test it was subjected to. But scientists have been trying to pin down precisely at what point Einstein's theory breaks down, and where an alternative explanation would have to be devised.
Einstein's framework for his theory of gravity, for example, is incompatible with quantum theory, which explains how nature works at an atomic and subatomic level.
Consider that for a black hole, Einstein's theory "predicts infinitely strong gravitational fields and density. That's nonsensical," said Paulo Freire, an astrophysicist at the Max Planck Institute for Radioastronomy in Germany and co-author of the study, which appears in the journal Science.
And so scientists are testing the general theory not because they think it is wrong but because they are certain it can't be the final explanation—just as Isaac Newton's notion of gravitational force was superseded by Einstein's.
Einstein's general theory of relativity states that objects with mass cause a curvature in space-time, which we perceive as gravity. Space-time, according to Einstein's theories of relativity, is a four-dimensional fabric woven together by space and time.
For example, a bowling ball causes a dent in a mattress, and that dent changes the otherwise straight motion of a nearby marble on the same mattress. Similarly, the mass of the sun distorts the space-time around it. A body with less mass, like the earth, travels along one path in that distorted space, which we call its orbit.
Dr. Freire and his colleagues put Einstein to the test in a cosmic laboratory 7,000 light years from earth, where two exotic stars are circling each other. One, known as a white dwarf, is the cooling remnant of a much lighter star. Its companion is a pulsar, which spins 25 times every second. Though the pulsar is just 12 miles across, it weighs twice as much as the sun.
"When you have such a big mass in such a small space you have extremely high gravity," said Charles Wang, a theoretical physicist at the University of Aberdeen, Scotland, who wasn't involved in the study.
The gravity on the pulsar's surface is 300 billion times as great as the gravity on Earth. The conditions there approach the relentless, overwhelming power of a black hole, which swallows even light.
"We're testing Einstein's theory in a region where it has never been tested before," said Dr. Freire.
The pulsar and white dwarf pair emit gravitational waves and the binary star system gradually loses energy. As a result, the stars will move closer to each other and orbit faster. Einstein's theory suggests the stars' orbital periods—the time they take to go around each other—ought to shrink by about eight-millionths of a second per year.
Dr. Freire's and his colleagues used several telescopes to take precise measurements of the two-star system. Their results perfectly matched the Einstein-based prediction.
Though Einstein's framework remains intact so far, "the study is significant for the way observations by astronomers are helping to identify new, extreme cases" to test his general theory of gravity, said Dr. Wang.
Einstein's theory was first—and dramatically—confirmed during a solar eclipse within four years of its publication, making him an instant celebrity. When asked how he would have felt if he had been proven wrong, Einstein replied: "I would have felt sorry for the Lord. The theory is correct."
Write to Gautam Naik at gautam.naik@wsj.com
A version of this article appeared April 26, 2013, on page A3 in the U.S. edition of The Wall Street Journal, with the headline: Einstein's Theory Proved Right—Again.

5 comentários:

Raul Abreu de Assis disse...

Einstein também escreveu um pequeno sobre suas impressões sobre o socialismo (1949). É interessante ler sua visão da sociedade e como, no final do texto, ele percebe claramente a ameaça do totalitarismo na tentativa de implementar uma economia socialista. Curioso também observar que ele não consegue oferecer nenhuma resposta para essa ameaça (e ele era um pouquinho inteligente).

Aqui tem um link para o texto:

http://monthlyreview.org/2009/05/01/why-socialism

Paulo Roberto de Almeida disse...

Conheço esse texto, e não o considero dos mais "inteligentes" (dentre os escritos fora da Fisica) de Einstein, até um pouco, ou bastante ingenuo, em relacao ao socialismo, mas ele devia estar influenciado ainda pelo clima da epoca, de triunfo do socialismo sobre o nazi-fascismo e todas as barbaridades perpetradas por este, esquecendo, talvez, que os principios econômicos eram quase os mesmos (com exceção da propriedade privada), e que o nazismo e o bolchevismo-stalinista estiveram não só aliados, objetivamente, mas eram irmãos-gêmeos no empreendimento totalitário. Hitler admirava a capacidade "destruidora" (assassina seria a palavra exata) de Stalin, e certamente quis excedê-lo no número de mortos (o que ele conseguiu, de forma concentrada, sendo superado por Stalin pelo período maior de extermínio, digamos assim, e ambos por Mao, que matou muito mais gente em doses concentradas).
Muitos intelectuais (e eu me coloco no rol) foram simpaticos ao socialismo, pela suposta igualdade, justiça, eliminação das "perversidades" do capitalis, etc.
Einstein caiu no conto...
Paulo Roberto de Almeida

Raul Abreu de Assis disse...

Com certeza o texto tem que ser lido dentro do contexto da época.

A parte que eu acho mais interessante é esta:

"Nevertheless, it is necessary to remember that a planned economy is not yet socialism. A planned economy as such may be accompanied by the complete enslavement of the individual. The achievement of socialism requires the solution of some extremely difficult socio-political problems: how is it possible, in view of the far-reaching centralization of political and economic power, to prevent bureaucracy from becoming all-powerful and overweening? How can the rights of the individual be protected and therewith a democratic counterweight to the power of bureaucracy be assured?

Clarity about the aims and problems of socialism is of greatest significance in our age of transition. Since, under present circumstances, free and unhindered discussion of these problems has come under a powerful taboo, I consider the foundation of this magazine to be an important public service."

A percepção clara da ameaça de totalitarismo e a defesa do livre debate.

O que os fatos da realidade têm mostrado repetidas vezes é que as tentativas de socialização da economia levam à pobreza e ao totalitarismo.

lgn disse...

Paulo, não se esquecer do Holomodor ucraniano, obra que é atribuída à Stalin. Um genocídio digno dos mais ambiciosos carniceiros.

Paulo Roberto de Almeida disse...

Sim, nessa história da Ucrânia, o Stalin até superou, antecipadamente o Mao: este matou muito mais, mas apenas de morte morrida, digamos assim, sem que ele quisesse necessariamente matar os chineses. O Stalin matou de morte matada, pois a intenção era realmente eliminar ucranianos, assimilados todos a kulaks antirevolucionários.
Dois celerados.
Veja estes videos:
http://youtu.be/EEu42L0ufBY

http://youtu.be/79HC57EagRQ

Paulo Roberto de Almeida