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COPERNICUS FESTIVAL, May 6-11, 2014, Kraków
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Probably the greatest scientific discovery ever achieved was made possible and intelligible by Einstein's development of new theory of gravitation. That theory gave rise to a prediction that the entire Universe, everything there is, is in a state of dynamic change -- a state of expansion. This rather revolutionary, because for thousands of years philosophers and scientists had believed that the space around us is ultimately static and fixed like a theatrical stage -- and on it were played out the motions of stars and plants and the other heavenly bodies.
Einstein predicted that there is no such fixed stage and the whole Universe ought to be in a state of change. That theoretical possibility was unrevealed and made clear by Alexander Friedmann and Georges Lemaître. Towards the end of 1920's Edwin Hubble and Milton Humason were able discover such a state to be observationally verified. What they did was to measure systematic shift in the colours of light from stars in distant galaxies and to show that that light was being stretched to longer wavelengths by the expansion of the Universe.
Paradoxically enough, life-supporting Universe is almost empty, big and old, dark and cold.
The type of building-blocks of biochemical complexity of which we are made do not come ready-made in the Universe. They are produced in the stars by long sequence of nuclear reactions and supernova explosions. The may even go through stars more than once. All the atoms of carbon within us have been made by simple nuclear reactions that combine two atoms of helium to make beryllium and then beryllium plus helium to make carbon and -- if you go further -- carbon plus another helium will make oxygen and everything heavier than oxygen. So all the carbon nuclei in the DNA-molecules have been through a star, but these processes take lots of time.
Because the Universe is going to need to exhibit billions of years of time to make the building blocks of life, if it is also expanding in the same period of time, it is going to became billions of light-years in extend.
For that reason, the Universe is virtually empty. If we were to take all the matter in the Universe and divide it into equally-spaced atoms, then there would be one atom on the average in every cubic meter of space. You cannot make a vacuum, which is empty as that in any laboratory on Earth.
The Universe is also very cool. Today the temperature is just about 2.7 degrees above absolute zero. And again -- this is a reflection of its enormous age and enormous amount of expansion that has taken place to give it that age. Every time it doubles in size, the radiation temperature halves.
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John David Barrow is an English cosmologist, theoretical physicist, and mathematician. He is currently Research Professor of Mathematical Sciences at the University of Cambridge. Barrow is also a writer of popular science and an amateur playwright.