A Perfect Balance
“We are an impossibility in an impossible universe.” ~ American author Ray Bradbury
As we have seen from the study of elementary particles, the stability of the universe appears precarious. Yet the cosmos endures, and likely will for its natural span.
That the universe exists at all is a miracle, in that all the fundamentals are in a perfect balance. Nature sings harmoniously.
Neutrons weigh 0.138% more than protons, their nuclear companion; exactly the ratio needed for nucleosynthesis: the creation of atomic nuclei in stars. Further, the electrical charge of electrons neatly balances that of protons. Without these precise proportions, matter could not exist.
Beyond hydrogen and helium, which are the lightest elements, stars make the material from which planets are constructed. In the process of nucleosynthesis, chemical elements are forged by fusion reactions in the hearts of stars. The heavier the element, the more massive a star must be to make it, and the trickier it is to create atoms which are stable.
Consider carbon, which would be inefficiently produced except for a special property – a resonance – that enhances production productivity. Carbon is the most versatile element in forming complex molecules. Life is based upon carbon-12, the most abundant isotope.* Carbon-12 only forms when 3 helium-4 particles combine in a certain way: a resonant combination called the Hoyle state.
(The production ratio of carbon-12 to carbon-13 is 99 to 1. With its extra neutron, carbon-13 is an oddball isotope.)
In 1954, Fred Hoyle made an outrageous prediction: that carbon-12 is carrying around an extra 7.65 million electron volts of energy. This special state is peculiar. One of Nature’s seeming chemistry conventions is that stability is only had when something is relaxed into its lowest-energy state. Instead, inscrutably, Hoyle was right. In 1960, American physicists confirmed the Hoyle state.
When stars run low on hydrogen to fuse into helium, their outer layers expand and redden while their cores shrink. During this inner contraction, helium nuclei – alpha particles – are forcefully fused, forming beryllium-8.
In the 10,000th of a trillionth of a second before the beryllium decays back into 2 alpha particles, a 3rd alpha particle may slam into beryllium-8. This threesome fusion of 6 protons and 6 neutrons – carbon-12 – is only stable if it packs an extra bundle of energy, arranged in the right resonance. If the strong nuclear force, which holds atomic nuclei together, was just a tad different, stable carbon could not be made, as the resonance of the Hoyle state would not be attained.
Adding another alpha particle to carbon yields oxygen. Due to the exact strength of the strong force, oxygen lacks the resonance that enhanced the efficiency of carbon creation. This prevents all of the carbon from being quickly consumed. Hence, the specific strength of the strong force gives a balanced mix of carbon and oxygen: exactly what the universe needs for life to take material form.
“Some super-calculating intellect must have designed the properties of the carbon atom, otherwise the chance of my finding such an atom through the blind forces of Nature would be utterly minuscule. A common-sense interpretation of the facts suggests that a super-intellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in Nature. The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question.” ~ Fred Hoyle
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The Sun is typical of stars in its modus operandi: fusion of hydrogen produces helium and radiates gamma rays. If such intense radiation was emitted, life would be impossible.
Instead, stars have a radiative zone, which is so dense that energy is absorbed and re-emitted. It may take a million years for a photon to make its way out of the Sun. By the time the energy reaches the surface and heads into space, emissions are primarily visible light and infrared radiation (heat): perfect for engendering life.
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Introduced by German physicist Arnold Sommerfeld in 1916, the fine-structure constant (denoted as α) states the strength of electromagnetism: how strong electromagnetic interaction is between elementary charged particles. This constant is equivalent to the elementary charge (e), which is the electric charge of a single proton or electron. The value of both these constants is 1/137.
Atomic nuclei all have positive charges, which naturally repel one another. Hence, the crunch of nucleosynthesis must be just-so forceful. As characterized by the fine-structure constant, if electromagnetism were only a wee bit stronger, the hearts of stars would not have enough power to bang out carbon. Conversely, if electromagnetism were but a tad weaker, carbon would simply be a step on the way to even heavier nuclei, no sooner made than consumed.
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An exhausted star that cataclysmically explodes in a supernova disperses its minted bounty into space, seeding the elements of planets, and of life. If the dynamics of stellar life cycles were any different, the cosmos could not exist as it is.
Sight Right for the Light
“The universe is not fine-tuned to us; we are fine-tuned to the universe.” ~ Victor Stenger
Life evolves to exploit its environment. The evolution of organisms is a goal-oriented (teleological) exercise. The light spectrum in which we see is exemplary.
All bodies emit a spectrum of light, with a peak wavelength output that depends upon the temperature of the body: the hotter the body, the shorter the wavelength at peak intensity.
Sunlight is smack in the center of our visual capability. The chloroplasts in plants and algae which photosynthesize are finely attuned to receive the most light that the Sun can provide.
Survival would be difficult if vision were set to the X-ray range, as there would not be much to see. The Sun casts scant X-rays.
Bees see light as we do, but their visual acuity also extends into the higher-frequency ultraviolet (UV) range. Plants know this, and craft their flowers to have patterns which specifically appeal to their pollinators and can only be seen by UV onlookers.
Animals’ bodies emit infrared radiation. Several different families of snakes independently evolved the ability to sense infrared, and so hunt in the dark for critters that cannot mask the rays thrown off by their internal body heat.