In the last quarter of the 19th century there was a long-running debate on the age of the Earth. In Charles Lyell's "Principles of Geology" (1830–33), he showed that the Earth had changed slowly, and that what we see is the result of gradual changes. This uniformitarianism clearly meant that the Earth was ancient, though Lyell did not try to work out how old.
His younger friend Charles Darwin believed this, too. Darwin saw that if evolution had taken place, it would have required a long time. Also, a huge amount of sedimentary rock lies between the early fossils in the Cambrian strata, and the present land surface. Darwin and Lyell agreed that it would have taken a very long time for so much rock to be deposited.
In the first edition of "On the origin of species" (1859), Darwin had estimated that the erosion of the Sussex Weald must have taken 300 million years. Both he and Lyell were surprised when the physicist William Thomson (Lord Kelvin) said the Earth could not be as old as they thought. He made the calculation based on how long it must have taken the Earth to cool down to its present temperature, given a starting point of 2,000C. Kelvin's result was based on the idea that the near-surface geothermal gradient reflects the conductive cooling of the solid Earth.
He did this calculation a number of times, making various assumptions. In 1862 his estimate was between 20 and 400 million years; but in 1866 he reduced the top estimate to 100 million years, and attacked Darwin and Lyle for not taking notice of his calculation. We know Darwin was anxious and worried that this would not be long enough to allow for evolution. Thomas Henry Huxley remarked that Kelvin's calculations were good, but his assumptions were wrong. In 1897 Kelvin did the calculation one last time, and came up with 20 to 40 million years. This, of course, would definitely not be long enough to allow for evolution. Oliver Heaviside also disagreed, and proposed an alternative geothermal model. Both Kelvin and Heaviside were eventually shown to be wrong.
Right at the end of the 19th century, someone realised that if the mantle was a highly viscous (sticky) fluid, that would make a great difference to the calculations. In 1895, John Perry, a former assistant to Kelvin, produced an age of Earth estimate of 2 to 3 billion years old using a model of a convective mantle and thin crust.
In Kelvin’s model, heat on the Earth’s surface
is derived from the cooling of a shallow outer crust, assuming a solid Earth. But if the conductivity inside the Earth were much higher than at the surface, then the Earth's core and lower mantle would also cool. This would provide a huge store of energy to the surface. In that case, Kelvin’s estimate of the age of the Earth would be too low by many times.
Perry's main reason was that convection in the fluid, or partly fluid, interior of the Earth
would transfer heat much more effectively than would conduction:
Kelvin stuck by his estimate of 100 million years, and later reduced the estimate to about 20 million years.
We now know that the existence of a viscous fluid under a thin crust is a much greater factor than the discovery of radioactivity, which was the textbook explanation for many years. The rediscovery and reexamination of Perry's work is quite recent.
In 1896 Henri Becquerel discovered radioactivity. In 1903, he shared the Nobel Prize in Physics with Pierre and Marie Curie "in recognition of the extraordinary services he has rendered by his discovery of spontaneous radioactivity".
Eventually, it was realized that radioactivity was a major source of heat inside the Earth. In 1921 came the first modern estimate, using radiometric dating. It was based on uranium-lead dating: the rate of decay of uranium to lead in the crust of the Earth, by Henry Norris Russell. He came up with 2 to 8 billion years. In 1949, H.E. Suess estimated 4 to 5 billion years, based on a whole array of radioactive isotopes. This is close to the time we estimate today, which has been refined further to about 4,560 million years.
The calculation makes use of convection in a viscous fluid as well as radioactivity, so it combines Perry's idea with the effect of radioactivity, even though Perry's contribution had been forgotten. The later knowledge of plate tectonics made it quite certain that the lower mantle was a viscous fluid.
The formation and evolution of the Solar System is estimated to have begun 4.568 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Basically, the whole system developed in the same period of time.
Use of the scientific method assumes uniformitarian methods for calculating Earth's age. The Hindu religion comes closest to the present-day scientific estimate. Some Christians and Jews believe the Genesis creation narrative is literally true, which would mean that the Earth was created between 5000 and 10,000 years ago, and the methods used to calculate age have not been consistent throughout Earth's history. However, these days most people think such questions are best answered by scientific methods.
Angara (rocket family)
Angara is a family of rockets which are being developed in Russia. The family contains many different rockets. For example, there is a rocket for lifting small payloads and a rocket for lifting heavy payloads. The rockets are designed by a company called Khrunichev State Research and Production Space Center. The first rocket is expected to be ready in 2012.
Angara is being developed using money given by the Russian government. The government decided to finance Angara because they wanted to make sure that Russia has independent access to space. Many of Russia's current rockets can only be launched from Baikonour Cosmodrome in Kazakshtan. Many of them also use foreign technology. However, Angara is better since it does not use any foreign technology (it is 100% Russian) and can be launched from Plesetsk Cosmodrome, located in Russian territory. Another reason why it was decided to build Angara is because Russia needed a rocket which does not use toxic fuels, like some current rockets do.
The first part of all Angara rockets consists of an engine called Universal Rocket Module (in short: URM). The small version, Angara 1.1 has only one URM, while the heavier Angara 5 has 5 URMs. For this reason, Angara 5 can lift heavier payloads. The second part (called the second stage) of Angara 1.1 is called Briz-KM and the second stage of Angara 5 is called Block I.
The rockets are meant for launching unmanned payloads such as satellites. However, Khrunichev has also suggested building a version that could launch humans into space: Angara 5P.
All Angara versions can be launched from a single launch pad.
The first flight of Angara is expected to take place in 2012 from Plesetsk Cosmodrome. In the future, the flights on Angara rockets will be sold to other companies, who want to get their satellites into space. The price for an Angara 1.1 flight is expected to be about 20 million dollars.
Samsara
Samsara is a Buddhist term, meaning the conditioned state of mind. It is the cycle of ignorance, leading to disturbing emotions and clumsy actions. They in turn are cause for suffering and new disturbing feelings and so on. According to Buddha’s teachings there are three main disturbing feelings: ignorance, anger and desire. They are called three poisons of mind and are told to have 84 000 combinations. The only way to completely get rid of suffering is to reach Nirvana or the perfect state of Buddha. All the teachings Buddha gives lead to this goal.
There are six realms of samsara, connected to six specific emotions:
Michael Heseltine
Michael Ray Dibdin Heseltine, Baron Heseltine (born 21 March 1933) is a British politician and businessman. He was a Member of Parliament from 1966 to 2001 as a member of the Conservative Party.