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Dark matter: dark energy: dark gravity

Tuesday 28th January 2014 @ 19:00

Non-Member: £12.00 ; Staff: £5.00 ; Student: £3.00


Dark matter and dark energy pervade the Universe.  What are they? How do we know they are there? How might they be linked? What might be dark gravity?

Professor Alan Heavens will explain how the Imperial Centre for Inference and Cosmology, ICIC, is going about answering fundamental questions about the universe.

He says, "Much of what we do in science is inference, which means we have some experimental data, from which we infer something about the Universe. For example we may wish to determine how fast the Universe is expanding, or what the properties of Dark Energy are. 

We can also ask broader questions such as whether the Big Bang model is the preferred theoretical framework, or whether Einstein's General Relativity is favoured over another gravity theory.  These are the sorts of questions I and colleagues at the ICIC address, through statistical analysis of cosmological data such as obtained from gravitational lensing, galaxy or microwave background surveys.

My specific interests centre on developing and applying the best methods for extracting information from data, such as: using the full 3D information from weak lensing surveys, and using size as well as shape information; transforming the data so that theory can be applied more effectively; compressing data in an optimised way so statistical analysis can be done very fast; looking for non-Gaussianity in the Cosmic Microwave Background and in the galaxy distribution. 

The scientific questions I am interested in include whether or not the acceleration of the Universe is due to Einstein's cosmological constant, Dark Energy, or alternative gravity models." 

Dark matter
Invisible dark matter makes up most of the universe – but we can only detect it from its gravitational effects.

Galaxies in our universe seem to be achieving an impossible feat. They are rotating with such speed that the gravity generated by their observable matter could not possibly hold them together; they should have torn themselves apart long ago. The same is true of galaxies in clusters, which leads scientists to believe that something we cannot see is at work. They think something we have yet to detect directly is giving these galaxies extra mass, generating the extra gravity they need to stay intact. This strange and unknown matter was called “dark matter” since it is not visible.

Unlike normal matter, dark matter does not interact with the electromagnetic force. This means it does not absorb, reflect or emit light, making it extremely hard to spot. In fact, researchers have been able to infer the existence of dark matter only from the gravitational effect it seems to have on visible matter. Dark matter seems to outweigh visible matter roughly six to one, making up about 26% of all the matter in the universe. Here's a sobering fact: The matter we know and that makes up all stars and galaxies only accounts for 4% of the content of the universe! But what is dark matter?

Dark energy
Dark energy makes up approximately 70% of the universe and appears to be associated with the vacuum in space. It is distributed evenly throughout the universe, not only in space but also in time – in other words, its effect is not diluted as the universe expands. The even distribution means that dark energy does not have any local gravitational effects, but rather a global effect on the universe as a whole. This leads to a repulsive force, which tends to accelerate the expansion of the universe. The rate of expansion and its acceleration can be measured by observations based on the Hubble law. These measurements, together with other scientific data, have confirmed the existence of dark energy and provide an estimate of just how much of this mysterious substance exists.

Professor Alan Heavens
Professor Alan Heavens is Director of the Imperial Centre for Inference and Cosmology. He holds an M.A. and Ph.D. from the University of Cambridge, and is a fellow of the Royal Society of Edinburgh and of the Royal Astronomical Society.

He is a member of the Planck and Euclid consortia and works on theoretical and statistical studies of cosmology, in large-scale structure, gravitational lensing, the cosmic microwave background, and galaxy spectra, and in the past has worked on particle acceleration in shock waves.

Professor Heavens is founding director of Blackford Analysis, a spin-out company from the University of Edinburgh which uses massive data compression techniques to analyse rapidlylarge data sets like those from medical scanners.

Optionally followed by supper (this can be booked on the event booking form).
After the lecture a Friends' Table has been reserved at a local restaurant to entertain the speaker and for any of the audience who would like to join us to continue the evening's discussion. A two-course fixed price supper is served including wine, coffee and service charge.

Venue: SAF Building, Imperial College London

Campus Map reference 33
on the Imperial College London Map