The dark skies of Dorset and Devon

The revolving roof inside the observatory tower at Belmont House in Lyme Regis

Observations of the Universe from Lyme Regis

Science feature by Professor Glenn Patrick

ONE of the benefits of living in Lyme Regis and much of Dorset is that we are in a part of the country where we can often appreciate the dark skies away from the bright lights of big towns and cities.

In fact, Cranborne Chase, which straddles the Dorset border with Wiltshire, was recently designated as an International Dark Sky Reserve and became only the fourteenth such reserve in the world. At 380 square miles, it has the largest central area of darkness of any of the dark sky reserves in the UK.

Here in Lyme, the expanse of empty ocean to the south and the (mainly) sympathetic street lighting cuts down on light pollution and enables us to see distant star constellations, planets and even the odd galaxy on a clear night.

I am sure this favoured position has encouraged a number of astronomers, past and present, to locate themselves in West Dorset and East Devon.

In 1884, an historic observatory was built at nearby Rousdon – just a few miles from Lyme Regis – by Sir Cuthbert Peek on his estate. For Victorian times, this was a substantial building and possessed a 6.4 inch refracting telescope.

Peek even employed a professional observer called Charles Grover who produced a notable catalogue of stars which change their brightness over time – known as variable stars. A frontier achievement in the 19th century!

Over at Salcombe Hill, near to Sidmouth, we also still have the working domes and telescopes of the Norman Lockyer Observatory, named after another Victorian astronomer.

Lockyer is jointly credited with discovering the gas helium in the Sun’s atmosphere and became the first Professor of Astronomical Physics at the Royal College of Science in Kensington. It was also Lockyer who named the newly discovered element helium – from the greek “helios” meaning the Sun.

He was duly knighted by Queen Victoria in 1897 and then retired in 1913 to establish his observatory in Salcombe Regis, which is a lasting legacy to Victorian astronomy.

The Victorian observatory tower in the garden of Belmont House

Returning to Lyme Regis, when travelling down the Cobb Road, I am sure you will have noticed the oddly shaped tower in the grounds of Belmont – the imposing Georgian villa that was once the former home of John Fowles.

This polygonal tower is in fact the survivor of another astronomical observatory dating back to 1881 when the Victorian GP Dr Richard Bangay bought Belmont as a family home.

Bangay was a keen amateur astronomer and copied the standard design of the Romsey Observatory (a sort of IKEA kit of its day) complete with a revolving roof. On open days held by The Landmark Trust, you can visit Belmont and marvel at the restoration of this iconic Victorian building by local volunteers.

Living in Dorset, the associations of novelist and poet Thomas Hardy are never far away. What perhaps is less appreciated is his fascination with astronomy.

It has been commented by a number of people that stars feature in every one of his novels and in a number of his poems. His romantic fantasy ‘Two On A Tower’ – first published in 1882 – even explored the life of a Victorian astronomer and his lover surveying the heavens from a tower on a private estate. One wonders where he found the local inspiration for his story!

In our modern times, we now have access to telescopes, binoculars and digital cameras to observe the majesty of the night sky. The beautiful photographs frequently published on social media of the Cobb or Durdle Door against the background of the Milky Way is testament to our continued fascination with our connection to the Universe and what lies beyond planet Earth.

For my part though, I often find my mind returning to a rather basic question which has profound significance. Why is the night sky dark and not bright? This became known as Olber’s Paradox, named after the German astronomer Heinrich Olbers, who encapsulated this ancient question in 1826.

Olber argued that if we live in a static, infinite, homogenous universe, then every line of sight should end on the surface of a star, which then would surely mean that the night sky should be bright and not dark!

In the same way that we cannot see through an infinite forest of trees without seeing a wall of tree trunks, we should see a “wall of stars” if we are surrounded by an infinite number of them. This paradox has challenged scientific minds across the centuries with numerous explanations, and even today textbooks often contain errors.

Hubble Ultra Deep Field image of 10,000 emerging galaxies. The deepest visible-light image of the cosmos – looking back 13 billion years when the Universe was only 800 million years old!

A clue to the answer can be found in the deepest view of the Universe from the Hubble Space Telescope. This famous image is of a small area of space, but in terms of depth it looks back 13 billion years – only 800 million years after the Big Bang!

This small element of space is estimated to contain 10,000 galaxies. An impressive number of galaxies and hence stars, but it turns out that these cover only 1 per cent of the sky – not anywhere near enough to illuminate the whole cosmos. We have to accept that the Universe is mostly an empty void, at least optically.

Strangely, the accepted answer to Olber’s puzzle has its origins in an observation by the poet Edgar Allan Poe who supposed “the distance of the invisible background to be so immense that no ray has been able to reach us at all”. In other words, there are simply not enough stars in the visible Universe to cover the sky.

Even if the Universe is infinitely large in extent, it is not infinitely old and has only been around since the Big Bang.

When we look back in space, we also look back in time and the maximum distance we can receive light is currently about 14 billion light years. This means that the portion of the Universe that is observable to us is finite.

If there are further stars beyond this limit, their light has yet to reach us. It is like looking for ships in Lyme Bay where we can only observe the sea to the limit of the horizon.

Another important factor in the riddle is that we now know that even those stars that sit within our visual limit only live for a finite age as they burn up their nuclear fuel. Yes, new stars are being born, but at a much smaller rate than earlier ages. So, the “forest of stars” is also gradually being depleted over time.

Next time you gaze up at the tapestry of bright stars in the Dorset night sky, it is worth pausing to also wonder about those black bits – for they are what truly connect us with the cosmos and still carry many of its secrets!

Glenn Patrick is a particle physicist and science communicator who explores the quantum world of sub-atomic particles (including at the Large Hadron Collider) and now lives in Lyme Regis

Woodmead Halls

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