What follows is based on part of ch. 2 of:

Spencer, Nick; Waite, Hannah. Playing God: Science, Religion and the Future of Humanity. SPCK, 2024.

A couple of recent discoveries:

Allan Hills 84001 – a meteorite originating from Mars, discovered in Antarctica in 1984 and in 1986 found to contain ‘possible relic biogenic activity’.  (Most experts would now doubt this analysis).

51 Pegasi b – an exoplanet discovered in 1995 orbiting around a sun-like star.

Such discoveries prompt speculation about whether life exists elsewhere in the universe.  And, if such life was intelligent, what would be its beliefs about God?

Some ancient thinkers entertained the possibility of ‘a plurality of worlds’.  Others, including Plato and Aristotle, believed that the earth, being at the centre of the universe, was unique.

Copernicus established that the earth is not the centre of the cosmos.  The development of the telescope prompted increased speculation about what might be ‘out there’.

Beginning in the early 19th century, there has been increasing interest in the possibility of communicating with inhabitants of other worlds.  By the middle of the 20th century, these attempts included the use of radio telescopes to search of signals.

The existence of exoplanets was confirmed in the early 1990s, and to date over 5,000 have been identified.  Of these, over 100 are earth-sized, and a number are in the habitable zone around their stars.  And some of these stars are promising candidates, by being stable, long-lived etc.  But habitability also depends on others factors – including the presence of carbon, hydrogen, nitrogen, oxygen, phosphorus, sulphur, and so on – but these elements appear to be quite abundant.

The Drake equation (1961) identifies some of the factors necessary for the existence of intelligent life, but its numerical estimations are inevitably vague.

There may be 5 billion potentially habitable planets in our galaxy, and there are at least 100 billion galaxies in the known universe.  Therefore, the number of candidates is stupendous.  The universe may be teeming with life.  This positive view is supported by the thought that life on earth began rather quickly, suggesting that it might be very ready to develop on other suitable planets.

However, a range of factors suggest a more negative view of the possibility of intelligent life elsewhere: not only the presence  of a habitable planet orbiting a suitable star, and the right chemical conditions, but also the evolutionary conditions, extinction events, historical accidents, and the tendency of our own ‘intelligent’ population towards self-destruction.

The balance, then, is between the very low chance of intelligent life developing and the very high number of potential candidates for it.

One cosmologist has suggested there there might be one intelligent civilisation in each galaxy at any one time.

Spencer and Waite conclude this section with:

‘Perhaps the rarity of the kind of life that can and wants to communicate with other similar kinds of life, and has the ability and the patience to listen for such communication – combined with the sheer distance such communication would have to travel – means that “everybody” is eternally just out of earshot.’

Comment

I think that this concluding statement is reasonable.  However, there is one critical factor that needs to be spelled out more emphatically:

In cosmological terms, ‘distance’ = ‘time’.  The further away an object is, the further back we are looking in history.

So, if we accept the suggestion that there is one intelligent civilisation in each galaxy at any one time, what would happen if we detected a radio signal coming from our nearest galactic neighbour, the Great Andromeda Galaxy?  That signal would have take 2.5 million years to reach us.  The chances of that civilisation surviving that that length of time (to say nothing of the further 2.5 million years required for them to receive our reply!) would seem impossiblity small.