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Are we alone in the universe?

By David Wilkinson

As a scientist and a theologian I am intrigued by the continued fascination with questions of aliens. In Superman’s new reboot, Man of Steel, Jonathan Kent says to Clark: “You’re the answer, son… to ‘are we alone in the universe?’” Of course, he is not the first parent to conclude that their children are not of this planet, but he does raise one of the biggest scientific questions of our time — are we alone?

However, are aliens science fiction or science fact? World UFO Day on the second of July wants to celebrate the possibility that we are a visited planet. Recently, the UK’s National Archives recently released documents covering the two years of the Ministry of Defence’s UFO Desk before its closure in 2009. Do drawings, photographs, and written descriptions of aliens and their spacecraft represent a conclusive answer?

While much of the public discussion of whether we are alone in the Universe is dominated by these images of science fiction or fascination with X-files conspiracy theories, scientists have in the last decade made considerable progress towards this big question.


Most prominently is the work which has led to the ‘daily planet’, that is, the fact I have a smartphone app which updates daily on the discovery of numerous planets outside of our solar system. The number of these exoplanets is now in the thousands and some may be Earth-like in their temperature, atmospheric composition, and their location orbiting stable stars. In the early 1990s we had no evidence for such planets, and we were unsure whether the Sun’s planetary system was a rare occurrence. Further, there was pessimism about the possibility of detecting exoplanets even if they were there. Stars emit a thousand million times more light than even the largest planets such as Jupiter. It is like picking out a light bulb beside a searchlight.

Brilliant new observational techniques have transformed this scene. First, a star should ‘wobble’ due to the gravitational pull of an orbiting planet. This can now be seen by the Doppler shift on the wavelength of light of the star, as an unseen planet tugs the star back and forth. This radial velocity method gives the radius of the orbit and the minimum mass of the planet. Second, if you were observing our solar system from far away, the movement of Jupiter in between your line of sight to the Sun would dim the Sun by one part in a hundred. NASA’s Kepler mission has been using this transit technique to search for planets around 150,000 stars since its launch in March 2009. It uses a specialized 0.95 metre diameter telescope called a photometer to measure the small changes in brightness caused by these passing planets. This remarkable instrument has been extremely successful in discovering new planets and identifying planetary candidates. The technique yields the orbit, the mass and the size of the planet. Then, from the orbit of the planet and the temperature of its star, the temperature of the planet is indicated. This information is very important as it indicates whether the planet is in the so-called ‘habitable zone’, where life could originate and evolve. In December 2011, Kepler 22b became the mission’s first confirmed planet in the habitable zone of a sun-like star: a planet 2.4 times the size of Earth.

So, it begins to seem that most stars have planetary systems. Thus, if there are a hundred billion stars in each of a hundred billion galaxies, then some will say that there must be another planet capable of life out there.

Yet we need to be cautious about thinking that the Universe is teeming with intelligent life. A planet needs to be ‘just right’ for life to evolve.  In addition, it is a long way from an amoeba to an accountant (or perhaps not!). There could be lots of bacteria but it may have not evolved to intelligence. Perhaps the strongest argument against other life came from Enrico Fermi. He argued that if the Earth is not special in having intelligent life, then civilisations should already have evolved many times in the Galaxy, since there are billions of stars older than the Sun. If any one of these civilisations wanted to colonise the Galaxy, they could have done so by now, even using technology that is almost within humanity’s grasp. So where is everybody?


The discovery of exoplanets highlights again the complex web of arguments of whether we are alone. It also focuses the question of what would be the effect if the Search for Extra-Terrestrial Intelligence (SETI) proved successful. Some have suggested that one consequence would be the demise of religion, as it will no longer be able to maintain the uniqueness of human beings or the special revelation of God, for example in the way the Christian faith sees the life, death, and resurrection of Jesus of Nazareth.

However, just as it would be wrong to jump to conclusions about aliens on the basis of the discovery of exoplanets, it would also be wrong to oversimplify the relationship between religion and SETI. In fact, some of the first scientists to speculate about life on other planets were in part motivated by their Christian faith. Astronomers such as Richard Bentley and Christiaan Huygens in the seventeenth century, impressed by the size of the Universe, speculated about life around the millions of stars and insisted this showed God’s ability to create life anywhere he wished, and that the Universe existed not for the sole benefit of human beings but to exhibit God’s glory.

The images of science fiction, belief in aliens, scientific arguments, and religious understandings all influence one another. As a Christian theologian who spent years as an astrophysicist, my experience is that SETI may not as yet have clear answers but that a consideration of the questions strengthens both my excitement with science and with faith.

David Wilkinson is Principal of St John’s College, and Professor in the Department of Theology and Religion, Durham University. He is the author of Science, Religion, and the Search for Extraterrestrial Intelligence. He is married to Alison and has two teenage children, Adam and Hannah. His background is research in theoretical astrophysics, where he gained a PhD in the study of star formation, the chemical evolution of galaxies and terrestrial mass extinctions. He also holds a PhD in Systematic Theology where he explored the future of the physical universe.

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Image credits: (1) UFO. © mchlhills via iStockphoto. (2) Andromeda galazy (2012) by NASA. Public domain via Wikimedia Commons.

Recent Comments

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  2. alyssa atwell

    It could be possible thatv we are not alone.. I beleive that we are a visited planet and I beleive we may have some unwanted visiters…. but yet I could bw wrong i m just sayin that there’s a high possibility

  3. […] University Press asks if are we alone in the universe, offers ten interesting facts about the Battle of Gettysburg, and discusses television sports theme […]

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