# Nova teoria da Idade do gelo



## Luis França (26 Jan 2007 às 18:18)

New ice age theory: Sun's 'dimmer switch'







Ice ages are not caused by planet Earth’s orbital variations as once thought, but by the dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years which is exactly the same period as between ice ages on Earth, according to a radical new theory proposed by renowned astrophysicist  Robert Ehrlich of George Mason University.

Ehrlich modelled the effect of temperature fluctuations in the sun's interior and showed that while the temperature of the sun's core is held constant by the opposing pressures of gravity and nuclear fusion, slight variations are possible.

His research builds upon the work of Attila Grandpierre and Gábor Ágoston who calculated that magnetic fields in the sun's core could produce small instabilities in the solar plasma inducing localised oscillations in temperature.

In an article appearing in the journal New Scientist, Ehrlich describes how some of these oscillations reinforce one another and become long lasting temperature variations, with the sun's core temperature to oscillating around its average temperature of 13.6 million kelvin in cycles lasting either 100,000 or 41,000 years.

According to the scientist random interactions within the sun's magnetic field could flip the fluctuations between the two cycles which correspond to the Earth's ice ages.

Over the past million years, ice ages have occurred roughly every 100,000 years and before that roughly every 41,000 years.

The currently accepted theories attribute the ice ages to subtle changes in Earth's orbit, known as the Milankovitch cycles, one of which describes the way Earth's orbit gradually changes shape from a circle to a slight ellipse and back again roughly every 100,000 years.

This should, in theory, alter the amount of solar radiation that Earth receives which in turn trigger the ice ages, but a hole in this theory has been its inability to explain why the ice ages changed frequency a million years ago.

http://pressesc.com/01169672696_


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## Minho (26 Jan 2007 às 22:46)

Se se conseguir de facto provar esses ciclos de intensidade no Sol para mim é uma das teorias mais convincentes...


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## Rog (26 Jan 2007 às 23:27)

É uma hipótese plausível... embora os ciclos de Milankovitch também façam sentido. Era importante tentar verificar se existe um padrão de intensidade por ciclos com duração de milhares de anos (além dos ciclos de 11 anos quando ocorre a mudança de polaridade do sol)...

(Um à parte; o artigo se estivesse em português facilitava a compreensão...)


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