Deep Time: Take Two

It's hard to fully comprehend the depth of time past. The universe came into existence some 13.8 billion years ago (BYA). The earth was formed around 4.5 BYA. The first signs of life – simple microbes – appear about 3.5 BYA. But as presented in a wonderful book about just how complex and essential they are – Life's Engines: How Microbes Made Earth Habitable by Paul Falkowski – microbes are anything but simple. Microbes – bacteria and archaea – are prokaryotes, single cell life without a nucleus or organelles. Everything else – single cell or multi-cell plants and animals – are eukaryotes: cells containing a nucleus and organelles such as mitochondria. The prokaryotes developed the ability to extract energy from the chemical environment and, eventually, from the sun. It took another two billion years for them to evolve into complex cells: the eukaryotes.

Two billion years is a long time. Why did it take that long to go from bacteria and archaea to the first eukaryotes? The machinery to convert chemicals such as hydrogen sulfide or ammonia, and then the much harder task of using sunlight, to fuel life would have taken a long time to develop. But not just that. Extracting energy from the environment meant a complex process of freeing electrons from chemical bonds, transferring those electrons around within the cell and using them ultimately to create other chemicals that would store those electrons (i.e., serve as “food”) to provide energy for cellular processes. Photosynthesis is an even more complex process that uses sunlight to crack electrons from water and combine them – through intermediate steps – with carbon dioxide to produce carbohydrates and, as a waste product, oxygen. This complex machinery had to evolve step by step through the repeated random changes in DNA and RNA as winnowed through natural selection. (A good part of the first billion years after the formation of earth would have been used for the construction of the RNA/DNA mechanism itself.) As Falkowski argues, the processes for producing and consuming biologic energy work as tightly as a complex and precise system of interlocking gears: one out of place and the whole won't work. All the parts of the machinery had to come on line more or less at once or it would not function. Somehow, the machinery evolved anyway, implying that a lot of time was required for vastly more failures – in which the resulting organism from random mutation simply died – than successes.

That the machinery was there to be evolved – that the givens of the universe allowed such a thing to come into existence – is also worth pondering. As is the fact that we would not be here otherwise.

Decoherence, or If a Tree Falls In the Forest...?

One of the basic unsettled questions of quantum physics is why we don't see quantum superposition in everyday objects. At the quantum level – and before being “measured” – mass and energy exist simultaneously as both wave and particle. The classic examples are light and electrons. Photons exist as both wave and particle and manifest as either depending on how it is observed. Similarly, electrons do not exist, in reality, as tiny “planets” circling the nucleus in neat orbits but in clouds of probabilities that may be “found” as a particle in a particular “place” only when measured. Everything that exists at the quantum level – the realm of the very tiny – shares this dual nature as wave and particle. It can be more accurately described as a wave function.

If everything were to remain in quantum superposition in the macro-world we inhabit, Schrödinger's cat – and everyone else's – would be both alive and dead at the same time. We don't see in that way because superposition seems to breakdown when things get large. The wave function has collapsed and we see either waves or particles, i.e., individual, unconnected, single state things. Why?

The easiest answer might be that we don't see quantum superposition at the macro level because when we look at the world, we as conscious observers collapse the wave function. Light, sound, touch, smell, taste all enter our perceptual mechanisms and, interacting with brain and mind, are perceived. The world is there when we observe it because the act of observation collapses the wave functions around us even if nothing else did. But does this mean that if a tree falls in a forest with no one there to hear it, it doesn't make a sound?

One answer might be yes, the unobserved falling tree makes no sound. The basic reality of the universe may be thought of as one all-inclusive wave function in which everything is entangled. The universe is one big cloud of probabilities. Nothing exists per se until observed. But that verges on solipsism. So, science has considered a variety of other mechanisms for decoherence of quantum superposition – collapsing the wave function of anything tiny before it can get very big. It may happen simply because as things get bigger, they get more complex. They interfere with each other, fall out of phase, or vibrate at different frequencies. The latest theory posits that as mass slows down – dilates – time, even the gravity of earth would be enough to pull entangled particles into different time streams.

But at least some aspects of the macro-world do work through quantum effects. The efficiency of photosynthesis arises from quantum mechanical effects. Quantum mechanics may explain how birds use magnetic fields to navigate and our sense of smell. It may be that the cosmos is an entangled universal wave function that decoheres only at the boundary of individual acts of “observation.” But the observers would not simply be conscious human beings but any living thing interacting with its environment? Might the definition of life be that which breaks wave functions?

Plants and the Sun

There's a fascinating article in the New Yorker on The Intelligent Plant.  It looks at the current debate among plant scientists over whether plants are intelligent or might be said to behave intelligently.  Plants do seem to interact with their environment in a way that appears directed and can often be quite complex.  But what caught my eye was the statement by one scientist to the effect that one does not have to ascribe intelligence to plants just to make them sound special as it's enough simply to note that they "eat sunlight."

We all learn about photosynthesis in school.  How sunlight is converted to free electrons within plant chloroplasts and made available to make carbohydrates from air and soil.  This is indeed wonderful enough.  But the notion that what plants are doing can be simply described as eating sunlight brings to the fore just how miraculous a process this really is.  Plants eat sunlight and we animals can then eat them and those that eat them for us.  Through the intermediation of plants, we too eat sunlight.  And it's free.

On a recent warm, sunny winter solstice day, sitting outside smoking a cigar, I looked anew at how this system works.  The universe is constructed in just such a way as to allow complex physics and chemistry to evolve giant balls of gas that release tremendous fountains of energy -- we call these stars, like our sun -- free to be consumed by stationary processing plants -- that we indeed call plants -- to also feed mobile creatures that may eventually achieve individual consciousness. 

Pretty cool.