Astronomers from around the globe are undertaking an ambitious project to build the world's largest optical telescope - the Extremely Large Telescope (ELT) - in Chile. This groundbreaking endeavor, scheduled for completion in 2028, hopes to offer answers to some of the most fundamental questions in astronomy and revolutionize our understanding of the universe.

Boasting a colossal 39-meter diameter primary mirror, the ELT promises to house the largest and most flawless reflecting surface ever created. This impressive feature will grant the telescope unparalleled light-collecting power, surpassing all other existing large telescopes combined. The ELT's heightened sensitivity will enable it to detect celestial objects millions of times dimmer than what the naked eye can perceive.

The construction of such a magnificent telescope holds multiple purposes. One of its primary aims is to capture images of the earliest galaxies ever formed, with light that has traveled for an astonishing 13 billion years to reach the ELT. The observation of these distant celestial entities has the potential to refine our understanding of cosmology and unravel the mysteries surrounding dark matter and dark energy.

However, the ELT's significance extends beyond unraveling the cosmos. It also holds the promise of shedding light on the age-old question: are we alone in the universe? Esteemed astronomers anticipate that the ELT will be the first telescope capable of identifying Earth-like exoplanets, which orbit stars outside our solar system and possess similar mass, orbit, and proximity to their host stars as Earth.

By locating exoplanets within the habitable zone, also known as the Goldilocks zone, where conditions allow for liquid water, scientists may uncover possible environments for life to thrive.

In terms of imaging capabilities, the ELT's camera is expected to offer six times superior resolution compared to the James Webb Space Telescope, enabling it to capture the clearest exoplanet images to date. However, capturing images alone will not provide a complete portrait of each exoplanet. To determine the likelihood of life on these distant worlds, astronomers will need to complement imaging with spectroscopy.

To address this need, the ELT will house four spectrographs. These advanced instruments will disperse light into its constituent colors, similar to the iconic prism on Pink Floyd's "The Dark Side of the Moon" album cover. Among the spectrographs, the Harmoni instrument will focus on analyzing the atmospheres of large exoplanets, searching for gases like water, oxygen, methane, carbon dioxide, and other potential indicators of life.

For the detection of smaller Earth-like exoplanets, the specialized Andes instrument, with an estimated cost of approximately €35 million (£30 million), will be indispensable. The Andes instrument's astonishing precision will allow it to detect minuscule changes in the wavelength of light, a result of the wobbling motion induced in the host star by the exoplanet's gravity.

By examining the subtle shifts in the star's emitted light, scientists can gather valuable data over extended periods, potentially unveiling the existence of an "Earth 2.0".

Researchers at Heriot-Watt University are also pioneering the development of a laser system called a frequency comb, which will provide the Andes instrument with the required precision. This innovative technology, akin to the tick marks on a ruler, will calibrate the Andes spectrograph, offering thousands of precisely spaced wavelengths to enhance its spectroscopic accuracy.

While some may question the €1.45 billion construction cost of the ELT, astronomy's profound significance transcends borders and cultures, offering insights that span millennia. Only by venturing far beyond our solar system can we truly broaden our perspective and gain a deeper understanding of the universe we inhabit.

With the completion of the Extremely Large Telescope on the horizon, astronomers are poised to embark on a new era of discovery, pushing the boundaries of human knowledge and transforming our understanding of the vast cosmos around us.