In this article by Loeb and Turner (2012), they propose the search for artificial illumination around Kuiper Belt objects on the outskirts of the Solar System. This would be a search for technologically advanced ET in our vicinity.
As one can see when flying at night during take off or descent into a big city, humans like to lengthen the duration of the ‘daylight’ using artificial light sources of lighting. Since our circadian rhythms have evolved to sleep when the Sun goes down, our eyes are not sensitive enough in low light conditions (night). Therefore, we try to illuminate our surroundings using fire and electricity for us to extend the hours we can work / recreate (or do anything), apart from sleeping. Since we as a species are very wasteful with little to no collective foresight, most of our sources of illumination are such that a huge fraction of the light they produce is wasted and radiated out into space. Below is an image which shows what the night sky looks like over various points on the Earth’s surface. This is an image created by piecing together numerous snapshots by NASA.
In this article, the authors propose a search for similar lighting around Kuiper belt objects (KBOs). Why KBOs? Perhaps since we have already looked at the moons of Jupiter and Saturn to rule out such ‘city’ sized illumination. However, I do not see the utility of such a search.
- A KBO at about 50 AU would experience about 0.04% the Solar Flux we receive on Earth. Would sunlight really be an efficient source of energy for a civilization there? What are the alternatives? Chemical or fossil energy also relies on a primary energy source which is Sun in the Earth’s case. An advanced civilization cannot directly start using nuclear energy. Therefore, barring solar energy, there is no energy source that a primitive life form can utilize and evolve along. Even if one argues that the amount of sunlight is sufficient for species to thrive (like deep in the ocean) or caves on Earth, then the question arises can it sustain an intelligent civilization like humanity with a power hungry ‘brain’?
- Moving on, if we argue that evolution is the mode by which life forms and transforms into intelligent life; then why will a ET civilization need bright Earth like lighting during their night time? Humans do not have night lights around their homes and cities which are 2500 (50AU ^2) brighter than our daylight. Our rods and cones will just saturate and perhaps even get damaged under such intense illumination.
- Further, from our line of sight (Earth) the KBO will ALWAYS have day time. Since the side facing us is to a good approximation, the side facing the Sun. Unless they want to artificially brighten their day side, we will not be seeing anything.
Therefore to summarize my arguments against such a search are –
- Plausibility of evolution of intelligent life on a KBO.
- The need for such bright light for an ET on KBO.
- We are always seeing the day side of a KBO from Earth.
Hence, I think such a search should not be conducted. Some of these points are mentioned in the conclusion of the paper, and it is correct that we cannot predict the nature of another civilization or its biology. However, the basic laws of Physics and Chemistry are universal.