IS THE MILKY WAY A LONELY PLACE IN THE UNIVERSE?

Is the Milky Way truly a lonely place in the Universe? The Andromeda galaxy (left) as seen by the Hubble Space Telescope (photo courtesy NASA); our galaxy, the Milky Way, as seen by the VISTA telescope (photo courtesy ESO). Courtesy ESO/NASA/Bell Burnell The discovery of hundreds of planets orbiting M dwarfs, which constitute 75 per cent of all stars in our galaxy, was a surprise for astronomers. If even one of these nearby planets were to harbour a dense atmosphere and liquid water – two key requirements for life – it would indicate that there are thousands of potential hospitable planets in our galaxy that we cannot currently detect. While M dwarfs emit less light into space compared to Sun-like stars such as the Sun, they also have narrower atmospheres. These two factors combine to reduce the steepness of the curve that measures the decline in the amount of visible, reflected starlight from a planet as you move away from it. If this curve flattens, it means that reflected light will travel much farther and be easier to detect. When you consider that there are 200 billion stars in our galaxy and 75 per cent of them are M dwarfs, as well as the fact that each M dwarf has approximately eight planets on average, the potential for habitability becomes even more astonishing. This discovery came as a surprise to astronomers, leading to the question of why we have been overlooking these countless possibilities for life. Fundamentally, the origin of life on Earth remains one of humanity's greatest mysteries. Why did it emerge here and nowhere else in the Universe? How did the complex chemistry required for life simply happen by chance? Chemist Christian de Duve's book Vital Dust (2002) beautifully summarises this conundrum. De Duve describes the fine line between mere matter and the emergence of life, stating that life arises when the atomic composition of matter becomes complex and structured enough to enable itself to repair any physical damage and reproduce again, actively passing down information encoded in DNA. Surprisingly, we are still relatively new to this field of study.

THE SEARCH FOR OUR PLACE IN THE COSMOS

Since humans first looked up at the cloudy veil of the Milky Way, we've been chasing the dream of understanding our place in the universe. The night sky's stars promise wonders, but the Milky Way itself is the biggest tease of all. We've sent spacecraft to explore its faintest reaches, but astronomers still haven't come up with a final tally on the possibilities for life in our galaxy. One study that rejigged the classic Drake Equation suggested, tantalisingly, that our galaxy might be… a little bit lonelier than we thought.

THE DRAKE EQUATION: REEVALUATING OUR GALACTIC NEIGHBORS

The Drake Equation rests at the centre of the probability matrix wherein we try to ballpark the number of other civilisations in the Milky Way. Originally conceived in 1961 by astronomer Frank Drake, it represents a mathematical shorthand for guessing at the number of civilisations with which we could, hypothetically, communicate. One of its most criticised aspects is its extreme reliance on the guesswork inherent in its overall assumptions.

CONTINENTS, OCEANS, AND THE DANCE OF PLATE TECTONICS: ESSENTIAL INGREDIENTS FOR LIFE

The existence of large landmasses and huge oceans, and the process of plate tectonics, provide rich terrain that can start moving up the complexity ladder. On Earth, a great deal of life originated only with the advent of modern plate tectonics, which led to a wide array of habitats for living things and to climate stability.

THE ROLE OF TECHNOLOGY IN CIVILIZATION'S DAWN

Civilisation, far from being something spontaneous, is the slow, creeping thing it is because the community had to learn to make tools, food, clothes, and weapons, by trial-and-error collisions with nature. It’s no coincidence that the really important human discoveries were fire, the introduction of the high-energy food source that set humanity apart, and electricity, our principal adaptation to darkness. The study points to the inevitability of fire and electricity; in fact, civilisation seems unlikely in places without either.

NAVIGATING THE UNCHARTED WATERS OF ALIEN INTELLIGENCE

The updated Drake Equation places a much more down-to-earth spin on the Galactic Club hopefuls, and cuts the prediction of communicative civilisations in the galaxy way back. While the old formula would have had them in the tens of thousands or millions, the new version suggests the number could be as low as 0.006 and as high as 100,000, with the average falling sharply at the bottom end of the spectrum.

THE GREAT SILENCE: ADDRESSING THE FERMI PARADOX

This updated figure in turn contributes to the enigmatic Fermi Paradox, pitting the likelihood of intelligent life against its stark absence, with no signs of contact or evidence. And as the study retools this debate, it invites a reconsideration of our expectations and methods for finding intelligent life beyond our planet.

THE FUTURE OF OUR GALACTIC QUEST

Although the improved Drake Equation gives a much better grip on the empirical question of how common intelligent life is in the Milky Way, it also points to the vast extent of our ignorance. How we find our fellow galactic citizens will be deeply speculative and clouded by uncertainty. With better estimates of planet formation and habitability, our predictions of alien civilisations will change.

UNDERSTANDING THE GALAXY

It’s a galaxy-sized dance of stars, planets and other bodies; a gravitationally bound star system that happens to be 100,000 light-years in diameter and contains hundreds of billions of stars, each one with orbiting planets of their own. The hunt for life among the stars challenges our intellectual limits and forces us to confront how unique we truly are.

No more than the canvas for our thoughts, no less than the cherished enigma in which we live and explore. Our galaxy, the canvas and the mystery, contains within its realm the great scale of existence, the minuscule details of the potential habitability. Peering into the void in search of life informs us, reminding us of the Universe’s seeming indifference toward our existence. It is an indifference that is truly a great mystery. With life in its broadest definition, the possibilities seem endless. We are bound together in a galaxy, the canvas and the mystery.