Final preparations are underway for the launch of a space telescope with the goal of creating the largest, most accurate 3D map of the universe and unraveling the dark forces that shape it.

The €1 billion (£862 million) Euclid probe from the European Space Agency will observe more than a third of the sky and billions of galaxies to shed light on the mysterious dark matter and dark energy that account for 95% of the universe.

“It’s one of the biggest questions in science,” said Prof Isobel Hook, an astrophysicist on the mission at Lancaster University. “We don’t know what the whole fabric of the universe is, which is huge. It’s our origins. It’s fundamental.”

With the launch of the James Webb Space Telescope, we might know the answers to a lot of questions. "What did the early universe look like?" is just one of them.#jameswebbspacetelescope pic.twitter.com/r0jNtcIbbT

— Al Mayadeen English (@MayadeenEnglish) November 6, 2021

Euclid will launch on a Falcon 9 rocket from Cape Canaveral in Florida at 11:11 am local time (1611 BST) on Saturday, beginning a one-month journey to its vantage point 1 million miles from Earth.

The spacecraft was previously scheduled to launch on a Russian Soyuz rocket in 2022, but the war in Ukraine ended cooperation between the ESA and the Russian space agency, Roscosmos. Hook said, “There’s a real buzz, it’s amazing,” adding that “this time last year, we didn’t know how the launch was going to go ahead.” More than 2,000 European scientists are involved in the mission.

What is the Euclid telescope?

The spacecraft, named after the ancient Greek founder of geometry, Euclid of Alexandria, is destined for a halo-like orbit around the sun-Earth Lagrange point two. The two-tonne probe can keep its back to the sun, shielding its sensors as it stares into space, thanks to the shared location with the James Webb space telescope.

Euclid is equipped with a 1.2-meter telescope, as well as two scientific instruments: an optical camera (Vis) and a near-infrared spectrometer and photometer (Nisp). While dark matter and dark energy are invisible, astronomers infer their existence from the gravitational pull they exert on galaxies and see dark energy at work in the universe's accelerating expansion.

What is its aim? 

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The six-year mission aims to map how dark matter clumps around galaxies and lay the groundwork for the cosmic web of matter that stretches throughout the universe.

Dark matter can be discovered through weak gravitational lensing, in which the mass of the invisible substance warps spacetime. Light bends as it travels from galaxies to the telescope, causing subtle distortions in their shapes.

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Scientists can infer where dark matter lurks and how dark energy has shaped the evolution of the cosmic web by analyzing the distortions of galaxies at different times and distances.

The Vis camera, developed by a team at University College London, will observe more of the universe in one day than the Hubble space telescope did in 25 years.

Although astronomers were aware of the universe's expansion in the 1920s, it wasn't until the 1990s that researchers, including Hook, discovered evidence that it was accelerating.

What is dark energy? 

Scientists proposed dark energy as a mysterious anti-gravity force that has increased in the last 6 billion years, causing galaxies to fly apart at an increasing rate.

Euclid scientists will measure the distances to millions of galaxies and examine how they are distributed in space to learn more about the nature of dark energy. Today, pairs of galaxies are typically separated by 490 million light years, but looking at the standard separation over cosmic history reveals how space has shifted over time. “We might confirm that dark energy is constant,” Hook said. “But it may not be constant, and we find that it’s not – that’s a very big discovery.”

While ordinary objects like stars and cars are made of atoms, dark matter is thought to be made up of exotic new particles that barely interact with ordinary matter.

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Detectors all over the world are looking for the mysterious substance, but so far they have all come up empty.

Dark energy is even more mysterious: scientists don't know whether the anti-gravity force is caused by quantum particles popping in and out of existence in the vacuum, an entirely new particle field, or if Einstein's general theory of relativity is simply incorrect.

Precision measurements from Euclid should aid scientists in determining which of the many dark matter and dark energy theories best describes reality.

"It's a fundamental problem to be in 2023 and not know what this large fraction of the universe is made of," Prof Mark Cropper of UCL's Mullard space science laboratory said, adding that “we have lots of theories but it’s hard to make progress without data. It’s like being in the dark ages.”