Understanding an expanding universe: How the Euclid probe will revolutionise the science of space

Telescope has begun releasing first images of galaxies that will ultimately look ten billion years into the universe's origin

Euclid’s view of the Horsehead Nebula. The mapping of the entire universe could change humankind's understanding of life. ESA

The discovery of the existence of dark energy – a mysterious force causing the expansion of the universe – is considered to be one of the greatest achievements in modern astrophysics, despite not being directly observed or measured.

Astronomers using the Hubble telescope in the late 1990s upended conventional thinking of how the universe operated, setting in motion decades of scientific investigation aimed at understanding what was going on. Gravity was supposed to be slowing down the expansion of the universe: so how was dark energy achieving the opposite effect?

One of those inspired to find answers was astrophysicist professor Andy Taylor, who was among a handful of scientists troubled enough by the baffling discovery to begin “scribbling” the outlines of a project on the back of envelopes or blackboards that would provide answers.

The acceleration theory “had caused a real problem,” Prof Taylor told The National at his University of Edinburgh office.

“If you think that you understand how gravity works, that you know all the forces of nature, then speeding up was not one of the possibilities so this has caused great confusion. It really is a huge mystery as to why on earth would the universe start accelerating?”

Prof Taylor has spent most of his career studying the nature of dark energy and dark matter, publishing works on the “very early universe”. He is currently the chairman of astrophysics at Edinburgh University.

Big picture

Finding answers to that formed the genesis of the Euclid project, a £850m unique spacecraft mission mapping the entirety of space, looking into more than ten billion years to peer deep into the universe’s origins.

It involves a 4.5-metre telescope to conduct a picture survey of the universe using a 600-megapixel camera. The device will create the most detailed 3-D map of the universe helping to understand dark energy and its implications.

Europe's Euclid space telescope was launched in 2023 to photograph most of the 200 billion galaxies or more and it has sent back its first images.

The results will probably transform the way we view the world around us, said Prof Taylor, who studied astonomy at Manchester University then "made a career out of what I loved".

The imagery could also reveal several challenging concepts: from unveiling alien civilisations to suggesting that we exist not in one universe but a multiverse.

“The Euclid mission has the potential to revolutionise our understanding of fundamental physics and the nature of our universe,” he said.

With Euclid now fully operational, he is leading the data analysis for Britain’s role in the project which he enthusiastically states could “change almost everything” in humankind’s knowledge.

This is, he admits, a “scary prospect” as he could be one of the scientists to see the first evidence of a new force in nature.

“If it changes our perception of quantum mechanics, it could change our perception of reality,” he said. “That there could be an extra dimension and if there’s an extra dimension in the universe, what's in that dimension? Why is it there? Why have we not noticed it before?”

Evidence of other universes might be a “crazy thing” but these are all possibilities of what Euclid could uncover.

What is dark energy?

Essentially, Euclid will create a map of the universe by observing study around five billion galaxies out to 10 billion light-years, across more than a third of the sky.

It will explore how the cosmos has expanded and examine the system’s most baffling elements, dark energy and dark matter.

Both are invisible, probably because they do not reflect, absorb or emit light, with dark energy, the name given to the mysterious force discovered in 1998 that was accelerating the universe and makes up more than 70 per cent of its mass.

Dark matter is described as the “cosmic glue” that holds billions of galaxies together providing the universe with about 25 per cent of its mass.

What they might be is what Euclid hopes to uncover. “We may have big gaps in our understanding of really fundamental bits of physics that we thought we knew,” said Prof Taylor, 57. “That’s the general concern, what are the knock-on consequences of that?

The solution was to build a camera powerful enough to photograph the universe and the European Space Agency agreed to fund the project mechanics at all, and we rely on quantum mechanics.”

New dimensions

Clearly the solution was to build a camera powerful enough to photograph the universe and the European Space Agency agreed to fund the project.

Scientists might already have discovered some of the universe’s secrets but the invasion of Ukraine set the launch back a year after the ESA ended its relationship with Roscosmos, the Russian space agency.

The Euclid spacecraft lifted off in 2023 on a Falcon 9 rocket from Elon Musk’s SpaceX company, and a month later the space telescope was stationed 1.5 million kilometres from Earth, in a stable zone just beyond the moon.

Also known as the Dark Universe Explorer, in a few days, its camera can map the equivalent of what the renowned Hubble has achieved since the pioneer space telescope was launched in 1990.

In the last few months, the first pictures have arrived and “it has blown everyone's mind, changing astronomy” with just a few image releases, said Prof Taylor.

Euclid will provide unprecedented data, possibly revealing new forces or dimensions and challenging humankind's understanding of quantum mechanics and reality.

The mapping will take six years – with enough fuel for another six – and Euclid has so far completed one per cent of its survey, more than what Hubble has achieved to date.

“We have already surpassed every other observation that's ever been done in this field,” Prof Taylor said. “The data is just awesome and it’s working perfectly and soon we're going to suddenly see the whole universe in high resolution. This is a step change for astronomy because astronomy has never had this volume or quality of data.”

The ambition is to measure the cosmos. “We need to turn the whole universe into a laboratory to understand what this dark energy is that's causing the acceleration.”

Extra dimensions

The scientist said there is growing speculation for the explanation of the universe's acceleration.

“They range from just introducing new forces into nature, which will be a big thing on its own, to maybe we need extra dimensions or a multiverse to explain it,” said Prof Taylor. “We’re at that level of uncertainty where we don't really know where we are any more with physics.”

But with Euclid providing the “ultimate view of the whole universe” its data will allow scientists to measure rates of acceleration potentially disclosing new forces of nature or dimensions.

“We need to map the whole universe because we need to get to that level of accuracy on the effects that we might see,” Prof Taylor said.

Obtaining “exquisite images of galaxies” means that Euclid, named after the Greek mathematician, will be “like no other experiment we've ever done before”.

Alien civilisation

The high precision measurements mean Euclid is not just a game changer for astronomy but also for understanding dark energy.

The volume of data will be so high – in the many millions of pictures – that no single human will ever be able to view its entirety in their lifetime.

However, people will be able to screen more initial images once they are released to the public by ESA later this year which could yield even more discoveries.

“There's a high probability that a member of the public finds something that no one has spotted,” said the scientist. “Someone out there may spot the ‘mother ship’ behind something or will see new alien civilisations that us scientists haven't seen because suddenly we are viewing the whole universe in high resolution for the first time. It's really exciting.”

Three of Euclid’s mass data releases will come out this year then one more two years later and the final instalment is likely in 2030.