The origin of galaxies – Malcolm Longair 1990 Christmas Lectures 4/5
In his fourth lecture Malcolm Longair explains the origins of galaxies.Watch all the lectures in this series here: https://www.youtube.com/playlist?list=PLbnrZHfNEDZy_oby1AwnVub0zqFr0Xfn2
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This lecture was recorded on 4 Dec 1990.
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From the 1990 programme notes:
How did the birth, life and death of stars begin? This is one of the great problems of modern cosmology. We know that a gas cloud collapses under gravity if it is large enough and this may well be the process by which stars form in galaxies. However, we need to consider the fact we live in an expanding Universe. The collapse of enhancements in the density of the Universe grow very slowly indeed. They should also leave an imprint of their formation upon the distribution of radiation in the Microwave Background Radiation, which has not yet been observed.
This suggests that we haven’t accounted for all the mass in the Universe. There must be a large amount of invisible matter present which only makes its presence known through its gravitational effect. Although we are certain that there is a large amount of dark matter, we are very uncertain about the form it takes. If the dark matter were in a form which only weakly interacts with ordinary matter, this could alleviate the problem of the lack of fluctuations in Microwave Background Radiation.
Fortunately, we are now able to study the Universe at epochs which are significantly earlier than the present and these provide some key clues about when the galaxies first formed. Out great hope is that, over the next 20 years, we may be able to define directly by observation, how it is that the large scale structure and the galaxies which define it came into being.
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About the 1990 CHRISTMAS LECTURES
The astronomical sciences have developed out of all recognition over the last 40 years. Up till about 1950, astronomy meant optical astronomy, but now it could mean radio astronomy, X-ray astronomy, infrared and ultraviolet astronomy, γ-ray astronomy and even more exotic ways of looking at the Universe through neutrino astronomy. Each of these disciplines has contributed essential new facts about the origin and evolution of different classes of object in the Universe. The aim of these lectures is to put all this new knowledge into a coherent picture of our present understanding of the origin and evolution of the Universe.
To solve the problems of the origins of astronomical systems, we must call upon an enormous range of physical tools to understand what it is we have to explain. We need to introduce many ideas from simple physics in order to define precisely the astrophysical problems which have to be solved. We will introduce these ideas as the lectures develop – we will need ideas like Newton’s law of gravity, the conservation of angular momentum, Einstein’s mass-energy relation E = mc2, simple ideas about black holes, nuclear reactions in stars and so on. We will introduce much of the essential physics through demonstrations, models and analogies. By the end of the lectures, we will not have answered the question of the origins of all the contents of the Universe but we will have gained an understanding of what the key questions are which still need to be addressed.
Find out more about the CHRISTMAS LECTURES here: https://www.rigb.org/christmas-lectures
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