The Question
It was one of those days when my science lesson had wrapped up early and we’d spent the remaining time looking at pictures from the Hubble telescope on our class projector. After talking about exoplanets, nebula, galaxies, and black holes the question came, “How did all of this happen? I mean. . .” One of my normally quiet students struggled for the words. ". . .can you just tell us everything?" ____________________________________ The universe began, as far as we know, as a tiny point with everything that ever has or that ever will exist compressed into an unimaginably small space. How this tiny point came to be we don’t know, though there are several interesting, and mind-bending, theories. From this single point all space and energy began to expand really, really fast.
Some of that energy settled down enough to become what we know as matter, specifically into particles of the simplest of elements: Hydrogen and Helium. Since gravity is the warping of space-time by matter, anything that has mass and takes up space, even tiny Hydrogen atoms, will begin to clump together under their own gravitational pull. As these clumps grew their mass increased which pulled in more and more particles. Eventually enough Hydrogen accumulated that the gravitational pressure kicked off the first nuclear reactions, and the first generation of stars were born.
As these stars burned through their hydrogen fuel atoms were torn apart and smashed together to create heavier and heavier elements within their cores.
Eventually forming the myriad of elements we now observe. Imagine, the gold in my ring, the calcium in your teeth, the iron in that chair – all of those atoms were forged in the cores of long-dead stars.
These new, heavier elements were then blasted out into space when those stars ran out of fuel and went supernova – forming new clouds of enriched cosmic dust and gas that would then collapse under their own gravity to form another generation of stars. As these stars formed, not all of the gas and dust would get pulled in - some particles formed a swirling disc around the star. These particles coalesced under their own gravity to form planets. Around one third generation yellow dwarf star, tucked away in a spiral arm of one of the hundred billion galaxies in the universe, eight such planets formed. The four inner planets were formed by the aggregate of the heavier elements, rocks and metals, that were closer to the star while the four outer planets were formed from the lighter gases swirling further from the star. These planets, obeying the law of inertia and the conservation of angular momentum, all continued to orbit the star in the same direction the dust and gas they formed from had swirled, and each spun upon its own gravitationally-determined axis.
The third planet in this solar system happened to orbit the star within the range at which liquid water could form. Not so hot that it would boil into vapor; not so cold that it would all freeze solid. At first, however, there was no liquid water on this world – only liquid rock. It took eons for the outer crust to cool and solidify, and even then a collision by another planet the size of Mars re-melted the surface and blasted material into a localized orbit around it – material which eventually coalesced to form the moon. Over time the surface cooled and solidified into rock, but molten rock continued to belch out from volcanoes that also released gases into space. These toxic fumes were kept from escaping by Earth’s gravity, and slowly accumulated to form an atmosphere.
Comets crash landed and slowly delivered water to Earth’s surface. Clouds formed by virtue of the physical and chemical properties of liquids which began the endless cycle of evaporation, condensation, and precipitation. In these first oceans organic molecules formed or were transported by asteroids and comets. By virtue of their chemistry these molecules could combine with each other in different ways. Eventually a simple string of organic molecules formed which could make copies of itself from the chemicals floating around it. The process of copying, however, wasn’t perfect, so variations began to crop up. Some of these variations were better at making copies than others, and so made more copies – natural selection had begun.
These primitive molecules evolved membranes and other specialized molecular machines to become the first proto-cells and, eventually, the first single-celled organisms. Some of these single-celled organisms grouped together to form colonies, which then began to evolve specialized functions to become the first true multi-cellular organisms. Some of these creatures used a series of chemical reactions to harness the energy of the sun in order to make their own food. Photosynthesis began, and one of its waste gases, oxygen, soon filled Earth’s atmosphere. As life evolved endless forms continued to reproduce with variation, and as groups of living things moved to different environments they varied in different ways. Eventually lobbed fish living in shallow tidal pools began adapting to spend more time out of the water. The land was largely empty, so there were no predators to worry about. Variations that could spend more time out of the water, and lay their eggs on land, survived and reproduced more than variations which could not. Over time, lobbed fins adapted to become legs and feet – and the first tetrapods walked upon the land.
Of these the reptiles proved most adaptable. . .for a time, growing to enormous size until an asteroid impact obliterated all large life forms on the planet. In the ecological space left over from these massive extinctions small, warm blooded creatures known as mammals survived and reproduced – with variation.
Some of these warm-blooded variations evolved larger, complex brains, learned to make tools, control fire, and began developing elaborate languages. Almost all of these larger-brained mammals went extinct, but at least one species survived as hunters and gatherers for hundreds of thousands of years. Then, at the end of the last ice age some ten thousand years ago, groups of these large-brained mammals discovered agriculture and began to domesticate animals.
By this time there were humans on nearly every continent, but plants and animals that could be domesticated only inhabited certain locales. Those geographic locations that happened to have large animal species that could be tamed and edible plants that could be farmed saw the birth of civilization. There, surpluses of food allowed people to devote time to things other than getting enough to eat for the year. Cities, complex governments, and religions formed as well as the first true attempts to understand the world.
Writing emerged, and for the first time information about the universe could be passed on not only through the genes of the fittest, but also by recording observations. It is this accumulation of observations, often imperfect and more than once interrupted, that led us to understand that the universe obeys a set of natural laws that can be understood. This realization prompted one such large-brained mammal to write, “. . .where the cause is not known the effect cannot be produced. Nature to be commanded must be obeyed. . .� Laying the foundation for what came to be known as the scientific method.
Using this method we can peer back through time; through thousands of years of knowledge interrogated from nature, painstakingly accumulated, and preserved across the ages, to understand the 14 billion year chain of events that led from an expansion of space and energy to living beings capable to contemplating the stars.
“Star stuff, contemplating the stars. Organized collections of 10 billion-billion-billion atoms contemplating the evolution of matter tracing that long path by which it arrived at consciousness here on the planet Earth and perhaps, throughout the cosmos.� --Carl Sagan