The Intergalactic Medium and Other Things – 23rd May 2013

Our May meeting was addressed by Alec Boksenberg, who gave us a lively talk about The Intergalactic Medium and Other Things. This was a very interesting and wide ranging talk including evidence that dark matter must exist. He said that although we can see its effects we do not know what it is but it is thought to be made up of sub-atomic particles. He explained that theobservable universe in the form of luminous suns, dust and gas only accounts for 5% of the total mass and that the missing 95%, which is made up of 23% dark matter and 72% dark energy, is detectable by gravitational effects. Information is obtained from observatories, Hubble, spectroscopy, infrared, cosmic background radiation, electromagnetism, photon counting detection, quasars etc. While evidence comes from the redshift of galaxies, galaxy rotation curves, X-ray emitting galaxy clusters, supernovae and gravitational lensing. He illustrated his talk with graphs and gave us examples. One of these examples was gravitational lensing whereby light from a quasar is bent around a galaxy which acts as a lens to produce two images of the quasar. Extreme mass is needed to produce this effect. He finished with the thought provoking question: Are we in a multiverse?

Alec Boksenberg is an eminent scientist who among his many achievements invented the Image Photon Counting System (IPCS), which is a camera that can detect optical and ultraviolet signals at the quantum level. This field has contributed significantly to the understanding how the Universe evolved from the Big Bang to the present day.

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