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  • Writer's picturePaul May

The Unknown Universe, by Dr Stuart Clark

From Dark Matter to New Observations: Challenging Our Current Understanding

The Season Opener and AGM Preview

To kick off our first lecture of the season, Dr Stuart Clark gave a fascinating and entertaining talk to a highly appreciative audience. Our auditorium was full and buzzing. The subject matter was nothing less than the origins of the universe! The warm-up act had been the AGM hosted by our chair Bobby Manoo, who provided a tantalizing glimpse of a packed lecture and event program for the coming year.

Probing the Universe's Origins

Stuart was covering less parochial matters—specifically, the scientific methods that underpin our current understanding of the universe's origin. First off was the famous cosmic microwave radiation map generated from data taken by ESA's Planck satellite. This map provides a window into the very early universe. The temperature variation of the radiation was used to confirm the prevailing theory of the universe's age and its constituents, including normal matter, dark matter, and dark energy.

Dr Stuart Clark and the Planck data

Challenging Established Models

But hang on, is this a matter of fitting the data to existing models, or could the data be telling us something else? Eddington had been an innovator in cosmology models, proposing nuclear fusion as the source of a star's energy. It was the only explanation that fitted with the observed data of stellar surface temperatures and elemental compositions. Only later, when neutrinos were predicted as a by-product and then measured, could this theory be confirmed directly.

The Mystery of Dark Matter and Dark Energy

Dark matter was initially postulated to explain the rotational speed of observed galaxies, assuming Newtonian gravity as correct. Similarly, dark energy was needed to account for observations of an accelerating universe through supernovae, consistent with special relativity. However, despite much effort over the last 40 years, neither has been directly observed.

Dr Stuart Clark at the Flamsteed Astronomy Society

Rethinking Cosmological Models

This leads to a tantalising question about the validity of our current cosmological models. Could a modified form of gravity, which reduces at large cosmological distances, as proposed by Milgrom, explain our observations without the need for dark matter? Recent observations from the JWST seem to show mature-type galaxies that appear to be 12 billion years old, but only 0.5 billion years after our universe's beginning. Current cosmological models could come under increasing scrutiny if these new observations are hard to reconcile. We live in interesting times!

What's Next?

Fittingly, our next main lecture on October 16th is "The Search for the Earliest Galaxies in the Universe with JWST" by Dr. Emma Curtis-Lake. We hope to see you all there.

Pictures from the Evening (by Mike Meynell, Gurinder Lall and Adrian Challinor):


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