The Wonder of Sunlight: Appreciating the Remarkable Coincidences that Make Life Possible
In recent articles (here, here and here), I have surveyed examples of properties of the periodic table of elements that appear to be designed to promote the existence of life. There is, however, a myriad of other features of our universe that appear to be delicately tuned for the existence of life — in particular, advanced life. Here, I will offer a summary of another class of such evidence — this one relating to the radiation emitted by the sun.
The Visual Band
The oxygen that we breathe is generated by the process of photosynthesis in the chloroplasts of green plants, a process that is energized by the light from the sun. Remarkably, the radiation emitted by the sun exhibits several remarkable coincidences that make life possible. Many forms of radiation make up the electromagnetic spectrum, each possessing a different wavelength. Within the inconceivably vast range of the electromagnetic spectrum, there exists a small band of radiation that possesses the right energy levels for photochemistry — allowing animals to see and green plants to photosynthesize. This corresponds to the visual band, together with the near ultraviolet and near infrared wavelengths that are closely adjacent to it. This band represents such an incredibly small fraction of the electromagnetic spectrum that it is difficult to do it justice. Concerning the inconceivable vastness of the electromagnetic spectrum, Michael Denton notes, “Some extremely low-frequency radio waves may be a hundred thousand kilometers from crest to crest, while some higher-energy gamma waves may be as little as 10-17 meters across (only a fraction of the diameter of an atomic nucleus). Even within this selected segment of the entire spectrum, the wavelengths vary by an unimaginably large factor of 1025 or 10,000,000,000,000,000,000,000,000.”1 The visual region of the spectrum represents a miniscule fraction of this, lying between wavelengths of 380 and 750 nm in length. Put another way, “the ‘right light’ would be only a few seconds in a time-span one hundred million times longer than the age of the Earth, or a few playing cards in a stack stretching beyond the galaxy of Andromeda — a fraction so small as to be beyond ordinary human comprehension.”2 It is a remarkable coincidence, then, that nearly half of the radiation emitted by the sun lies within this visual region.
The Infrared Region
As to the other half of the sun’s radiant output, this lies primarily in another infinitesimally small region of the spectrum that is adjacent to the visual region, between the wavelengths of 750 to somewhat beyond 2,500 nm. This infrared radiation provides approximately half of the essential heat that is needed to warm the atmosphere of our planet. Denton remarks, “Without it Earth’s entire surface would be a frozen wilderness far colder than the Antarctic. It is thanks to the heat of the sun (and to our atmospheric gases absorbing this heat) that water exists in liquid form on Earth’s surface and the average global atmospheric temperature is maintained well above freezing, in a temperature range which enables the chemistry of life to proceed.”3
Denton concludes, that “this is a genuine coincidence, as the compaction of solar radiation into the visible and near infrared is determined by a completely different set of physical laws from those that dictate which wavelengths are suitable for life and photosynthesis.”4 One might be tempted to ask here whether, given the sheer number of stars in our universe (conservatively estimated at 1024), our sun might be the lucky winner of a cosmic lottery. But, in fact, most stars emit the majority of their radiation in the visible and infrared region.
Penetration of Visual Light
Of course, photosynthesis also requires that the visual light be allowed to penetrate the atmosphere and reach the ground, and that part of the sun’s infrared radiation be absorbed in order to warm our planet to the degree that photosynthesis can take place. It is an exquisitely fortuitous coincidence, then, that Earth’s atmosphere not only allows penetration of almost all of the radiation in the visual region, but also absorbs a significant proportion of the infrared radiation, thereby warming the Earth into the ambient range. In addition, our atmosphere absorbs the dangerous radiation on either side of the visual and near-infrared regions of the spectrum.
Finally, in order for photosynthesis to take place, the visual light must be able to penetrate water, since the light must traverse the water in the cell of any green plant in order to reach the chloroplasts. And, indeed, water — whether in its liquid, gaseous or solid form — is transparent to visual light. If the water vapor in the atmosphere or the liquid water of the cell absorbed the visual band, there could be no photosynthesis, and no aerobic form of life would exist.
Remarkable Coincidences
Photosynthesis is absolutely essential to the existence of advanced life forms. And yet it is easy to imagine a plethora of scenarios where, if our universe were just slightly different, photosynthesis could not take place, and no aerobic forms of life could exist. Since advanced life is not particularly surprising given theism but extremely surprising given naturalism, this evidence tends to confirm the existence of a creator. For a much more detailed discussion of the properties of sunlight that make advanced life possible, I recommend Michael Denton’s book, Children of Light: The Astonishing Properties of Sunlight That Make Us Possible.
Notes
Michael Denton, Children of Light: The Astonishing Properties of Sunlight That Make Us Possible (Discovery Institute Press, 2018), chapter 2.
Ibid.
Michael Denton, The Miracle of Man: The Fine Tuning of Nature for Human Existence (Discovery Institute Press, 2022), 52.
Ibid.
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