The Generosity of the Sun

Totality.

Totality.

 An essay dedicated to the Faithless Generation.

For since the creation of the world God’s invisible qualities- his eternal power and divine nature –have been clearly seen, being understood from what has been made, so that people are without excuse. For although they knew God, they neither glorified him as God nor gave thanks to him, but their thinking became futile and their foolish hearts were darkened. Although they claimed to be wise, they became fools..

                                                                                                          Romans 1:20-23

Coincidence is God’s way of remaining anonymous

                                                                      Albert Einstein (from The World As I See It)

When the Moon formed, it was much closer to the Earth, and has been steadily retreating as the energy of its orbital motion has gone into stirring up tides….. Just now the Moon is about 400 times smaller than the Sun, but the Sun is 400 times farther away than the Moon, so that they look the same size on the sky. At the present moment of cosmic time, during an eclipse, the disc of the Moon almost exactly covers the disc of the Sun. In the past the Moon would have looked much bigger and would have completely obscured the Sun during eclipses; in the future, the Moon will look much smaller from Earth and a ring of sunlight will be visible even during an eclipse. Nobody has been able to think of a reason why intelligent beings capable of noticing this oddity should have evolved on Earth just at the time that the coincidence was there to be noticed. It worries me, but most people seem to accept it as just one of those things.

                                                                   John Gribbin (from Alone in the Universe)

The noted science writer and astrophysicist, Dr. John Gribbin, raises an interesting point at the end of the excerpt from his 2011 book, Alone in the Universe, quoted above. He describes the coincidence of a total solar eclipse and the emergence of a global human technical civilization as something that ‘worries’ him. I can well understand that position given the inadequacy of the blind forces of Darwinian evolution to explain why these events are coincident in cosmic time. But that’s only an issue if one assumes biological evolution to be watertight. A more rational, and dare I say, compelling answer to Gribbin’s conundrum is that these events are not mere coincidences but were pre-ordained to occur in a unique window of cosmic history to reveal the attributes of an all powerful Creator; a personal God who, like a great king, wishes to demonstrate His omnipotence to an unbelieving population.

Such a world view, which is currently counter to the prevailing secular corpus of scientific thought, would be strengthened if other attributes of the Sun were found to be odd, peculiar or even unique. Intriguingly, great advances in our knowledge of the Sun over the past 30 years has yielded a solid body of evidence pointing to the possible uniqueness of our Sun, the yellow star that has presided over the extraordinary allegory of events that culminated with a global human technical civilization in the present epoch.

                                                Peculiar formation history

Diligent research over the past century has revealed that stars are not born in isolation but are hatched in their thousands inside enormous clumps of gas and dust. Our Sun was formed from the fragmentation of one such cloud under the auspices of magnetic and gravitational forces that led to the contraction of one cloud fragment, culminating with the ignition of the nuclear fires at the centre of the proto-Sun and the formation of a disc of gas and dust in the plane of the solar equator that would form the elegant planetary system we live in today. Yet the Sun was formed with an unusual assortment of heavy elements that originated in not one but two distinct kinds of supernova events that must have occurred in close proximity to our neonatal solar system to enrich it with those elements. What is more, our solar system was formed during the epoch  when the interstellar medium was maximally enriched with the long-lived radionuclides thorium-232 ( half life 14.1Gyr), uranium-235 (half life 0.704 Gyr) and uranium-238 (half life 4.468 Gyr); elements that provided Earth with the thermal energy to maintain plate tectonics on our planet over geologic time. Without large quantities of these elements, the Earth would have been just another lifeless planet.

But forming the right kind of star and the right kind of planets was still not enough though. Had the Sun and its retinue of planetary bodies remained entangled in the star cluster of its birth for very long, gravitational interactions with nearby stars would have wreaked havoc with our orderly solar system. Moreover, had the Sun formed as part of a binary or multiple star system – as have as many as 70 per cent of sun-like stars in the Galaxy – it would have been game over for a life bearing planet like the Earth, as it would not have able to maintain a stable circular orbit about the Sun over the entire duration of its history. For the Sun and its family of planets to proceed to the next stage of development, it had to be ejected from the cluster of its birth to live in safe isolation from the rest of its stellar siblings.

                                              Peculiar physical properties

In the early 19th century, the German optician, Joseph von Fraunhofer (1787-1826), founded the science of stellar spectroscopy. By attaching a diffraction grating to his achromatic refractor (both of his own design) he was able to demonstrate that stars like Sirius differed significantly from the Sun.

Joseph von Fraunhofer demsonstrating the spectroscope.

Joseph von Fraunhofer demsonstrating the spectroscope.

Today, we follow in the great optician’s footsteps, employing diffraction gratings to obtain high resolution spectra of a multitude of stars, allowing astronomers to perform a so-called differential element analysis on a large stellar population.These and other techniques have revealed a curious truth about our star, the Sun. While it is easy to find twins of almost any other star, an exact solar twin has yet to be found. And though quite a few stars can be matched to the Sun with respect to its basic parameters like mass, age and luminosity (G2V spectral class), the Sun stands out like a sore thumb with respect to these solar analogues, showing a 20 per cent depletion in certain refractory (non-volatile) elements such as calcium, aluminium, magnesium and silicon; the elements that wound up inside the rocky terrestrial planets of our solar system.

 The Sun, though widely reported to be an ‘ordinary star’ is actually more massive than 95 per cent of all other stars in the Galaxy. The vast majority of stars, the teeming multitudes of red and brown dwarves, are too cool to hold planets at a safe distance from their fiery surfaces in order that liquid water could be profitably maintained on their surfaces over the aeons. Such stars would need to spawn planets very close in – typically an order of magnitude closer than Mercury is to our Sun – causing them to become tidally locked. This means that they would keep the same face to their parent stars in much the same way our Moon does while orbiting the Earth. This scenario would render life incredibly difficult on such planets. After all, the permanently illuminated hemisphere would be incinerated while the other would be in a perpetual frigid darkness. Lower mass stars, by their nature, emit less ultraviolet (UV) radiation too – a plus you might think – until you learn of how important UV radiation is for generating and sustaining the ozone layer. And no ozone layer would make life very difficult indeed on the landmasses of any putative world orbiting these low mass stars.

But there are yet other perils that attend stars with lower masses than the Sun. In the summer months, I use my 3 inch classical refractor to project an image of the Sun on a piece of white cardboard or by using a full-aperture solar filter. More often than not, I can make out small sunspots – regions of intense magnetic activity that correspond to cooler regions of the solar photosphere – that make an otherwise bland solar disc all the more interesting to observe. Sunspots though, are also strongly correlated with flare activity and it is not an inconsiderable fact that stars even a little lower in mass than the Sun have significantly higher activity in this regard. Ongoing solar research suggests that during sunspot maximum (which follows a roughly 11 year cycle) our Sun already has the ability to inflict potentially serious damage to living cells, as well as hampering human telecommunication  systems, so that any significantly greater activity would prove disastrous for life on Earth in general and human civilization in particular.

Sol, as it appeared at appeared on the sunny afternoon of May 7, 2013.

Sol, as it appeared through the author’s 3-inch Fraunhofer refractor  on the sunny afternoon of May 7, 2013.

The tiny fraction of stars in the Galaxy larger than the Sun have very short lifetimes (scaling with mass as M^-2), insufficiently long to allow even microbial life (if it exists at all) to start the process of heavy metal concentration – which include the so-called ‘vital poisons,’ as well as the heavy metal deposits needed to sustain a high-technology society – in their planet’s crust.

                                                           Peculiar stability

How does flare activity correlate with stellar age? It turns out that solar flaring has continued to decline over time, reaching a minimum in the present epoch, roughly half way through the life of our star and dovetailing nicely with the emergence of humanity in the solar system. What’s more, sensitive measurements reveal that our star varies less in luminosity (typically by less than 0.1 per cent) than any known star.

                                                       Peculiar kinematics

In 2008, a team of astronomers led by Charles Lineweaver based at the Australian National University, conducted a study on a large body of stars taken from the Hipparcos archive and discovered that the Sun has a more circular orbit than 93 per cent of other stars in the distribution. Safely tucked away between spiral arms near the co-rotation axis of our Galaxy (a peculiarly stable place to be!), some 27,000 light years from its centre, we live on a planet spared the deadly effects of short wave radiation that have surely sterilised the down town regions of the Milky Way. Out here, in Galactic suburbia, we move around the centre of the Galaxy once every 0.25Gyr, enjoying transparent, dark skies that allow us to look all the way back in time to the earliest epochs in cosmic history, so enabling humans to elucidate the physical events that shaped the unfolding cosmos in which we find ourselves in.

Stars not only move within the plane of the Milky Way’s thin disc but oscillate up and down as they orbit the Galactic centre. Many years of kinematic studies conducted by astronomers show that its amplitude of oscillation is smaller than many stars in the solar neighbourhood which makes the solar system less susceptible to gravitational perturbations that could potentially destabilise established planetary orbits. Indeed, according to the stellar astronomer, Dr. Guillermo Gonzalez, the Sun’s kinematic attributes are more reminiscent of a young star than one that is 4.57 billion years old!

                                                            Not forever!

As I have attempted to outline thus far, it seems patently clear that the Sun is a very unusual star enjoying a rather unusually stable phase in its life. Over billions of years since its birth, the Sun has grown steadily brighter and life on Earth, particularly the green plants, have worked to compensate for the Sun’s increasing luminosity by removing more of the greenhouse gases (particularly carbon dioxide and water vapour) from the Earth’s atmosphere. But the unchanging laws of physics that govern the Sun’s evolution are the same yesterday, today and tomorrow. This means that the Sun is going to continue to brighten and heat the Earth’s surface. But the levels (currently 392ppm) of carbon dioxide needed to conduct photosynthesis are already close to the minimum necessary (~150ppm) to sustain vigorous plant growth. Clearly, the current situation cannot be maintained indefinitely. Likewise, as it continues to evolve (and stars really do evolve because there is a robust physical theory underpinning that process), flare activity will increase to a point where large animal life cannot be sustained. Clearly therefore, we are living in the best of times.

                                               Just one of those things….

Sol Invictus!

Sol Invictus!

 

 

I suppose one could always shrug one’s shoulders and say something like, “that’s a strange coincidence,” or “it’s mere chance.” But, these answers are not very satisfying to a curious intellect; an intellect hard wired to spot patterns. Cast your mind back once more to the exquisite geometry of a total solar eclipse. A few million years ago, the Moon’s apparent diameter was larger than the Sun’s and the non-human primates – Homo Erectus or some such – that inhabited the Earth at that time, lacked the sophistication – both mentally and spiritually – to appreciate the event. In a few million years hence, the Moon will be smaller than the Sun’s face and the Earth will be unfit for human habitation. Only at a time sandwiched neatly between these epochs did creatures with the necessary cognitive capacities emerge on the scene to understand the significance of this alignment, allowing them to deduce both the geometry and scale of the solar system. Even the mind-boggling logic of Einstein’s theory of general relativity was confirmed during a solar eclipse.

Do you really think these solar peculiarities are just coincidences? How many coincidences and peculiarities does one need to convince one of a greater, underlying truth about the Sun and our relationship with it? And where does Darwinian evolution – the ‘blind watchmaker’ – fit into all of this?

Thank goodness for small mercies!

If you’d like to hear more amazing coincidences about the Universe we inhabit, you might be interested in my new book, Grab ‘n’ Go Astronomy, due out this Summer.

 

De fideli

This essay was inspired by the continuing work of Dr. Hugh Ross, Founder & President of Reasons to Believe and colleagues; truly a candle shining in an ever growing sea of darkness.

Some References for Further Study.

Barrow J.D. & Tippler, F.J. (1988), The Anthropic Cosmological Principle, Cambridge University Press.

Ross, H. (2008), Why the Universe is the Way it is, Baker Books.

Ward, P.D, & Brownlee, D, (2000) Rare Earth: Why Complex Life Is Uncommon in the Universe, Copernicus.

Gribbin, J, (2011), Alone in the Universe, Wiley.

Philips, A.C. (2001), The Physics of Stars, Wiley.

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