Out into the Universe - Introducing Cosmology -

Dr Akihiro Ishibashi

Saturday, 7 February 2004; 7:30-9:30pm

Keynes Hall, King's College

'Cosmology' addresses the origin and evolution of the Universe through laws of physics. This talk is, hopefully, a pedagogic account of basic ideas and recent progress in Cosmology, with the aim of raising interest in current research about our Universe.
Main focuses are:
(I) Is our Universe really full of stars and galaxies? ('Dark-energy' rules the world)
(II) Why is our Universe so smooth and uniform? (The 'Inflation' scenario saves the Big-Bang Theory)
(III) Where are we living? (Possibly on 'a' universe in some 'dimensionally larger' space-time)
Level: The talk will not require any scientific knowledge beyond an elementary level.

1. Dark-energy: A type of the energy which is needed to explain why the present universe is speeding up its expansion. It may also be called 'Quintessence', 'Cosmological Constant', or 'Vacuum energy'.
2. Inflation: A brief period of very rapid expansion at the very beginning of the universe. The standard Big-Bang Theory cannot explain why our universe is so large, why so smooth/uniform on large scale, and how the cosmic structure originated. "Inflation" is a possible and promising idea to solve these problems. Dark-energy---often called 'vacuum energy' in this context---plays an important role as a driving source of the inflation.
3. Space-time dimension: Imagine, an ant who is walking on a plastic film/sheet. It can recognise that the film/sheet has [length] and [width], but cannot see the 3rd direction [height]. Hence it may believe that it is living in a "2-dimensional" world. We normally recognise that the world is a "3-dimensional space" ([length], [width], and [height]), plus one more direction/dimension [time] (Our universe is therefore said to be a 3+1=4 dimensional space-time).
However, recent developments of 'Theory of Everything'---which is still in its infancy, though---suggest that our universe may be something like a "film or sheet" of 3-dimensions, and there may exist extra space directions/dimensions outside our universe. Our usual understanding of the universe might be more or less the same as that of the ant.