The more the universe seems comprehensible, the more it also seems pointless.
Steven Weinberg, The Last Three Minutes
Every one of us is, in the cosmic perspective, precious. If a human disagrees with you, let him live. In a hundred billion galaxies, you will not find another.
Carl Sagan, Cosmos
Let’s pause for a moment and think about the following: Where does the matter that compose your hands, feet, head, etc. come from? Most people rarely think about it. As it happens, it is an extraordinary story that took scientists many decades to figure out. As shown in Table 1 below, The Cosmic Calendar, the “story” starts with the origin of the universe, known as the Big Bang, and culminates with the appearance of humans, just in the last 8 minutes of the cosmic year.
Table 1 shows a summary of the Cosmic Calendar, which “compresses” the history of the universe from its origin, the “Big Bang,” about 13.8 billion years ago, to today into one calendar year. In this visualization, popularized by the late physicist Carl Sagan in his book The Dragons of Eden (1977), the Big Bang took place at the beginning of January 1 at midnight, and the current moment maps onto the end of December 31 just before midnight. I have focused mainly on the events in “December”, when life first appeared on Earth. To see a more complete list of events see, e.g., Wikipedia. The Cosmic Calendar.
As a description of the origin of the universe, the Big Bang has a significant connection with religion and philosophy. Some believe the Big Bang implies a creator, and some see it mentioned in their holy books. In fact, many believe that the whole purpose of the creation of the universe is us, humans. There is no way to scientifically prove or disprove this claim (science is better at finding things that exist than at ruling out things that do not). There is, however, compelling evidence that the universe is the product of natural not supernatural causes, that it obeys the laws of matter, and that it is not advancing towards a goal or “grand plan.”
Let’s look at the evidence
One of the most intriguing findings in the last few years is that the universe is expanding at an accelerating rate. Instead of slowing down from cosmic gravity, as cosmologists had presumed for a century, galaxies started speeding up, six billion years ago. Imagine tossing an apple in the air and watching it go up faster and faster rather than falling back down. The cause behind this accelerated expansion is the so-called “dark energy” that, together with “dark matter”, represents the largest mass in our universe.
Dark matter is called “dark” because it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect, or emit electromagnetic radiation and is, therefore, difficult to detect. Astronomers have inferred the existence of this matter to account for gravitational effects that cannot otherwise be explained by currently accepted theories of gravity. For this reason, most experts think that dark matter is abundant in the universe and has had a strong influence on its structure and evolution.
It turns out that only 4% of the universe is made of “ordinary” atoms like those that make people, cars, iPhones, and everything else that we know. About one fourth of the universe is composed of dark matter and the remaining and largest portion is dark energy.[1]
If things keep going the way they are, physicists estimate that in 100 billion years the only galaxies left visible in the sky will be the half-dozen or so bound together gravitationally into what is known as the Local Group, which is not expanding, and in fact, it will probably merge into one starry ball. This means future astronomers will be unable to see any galaxies flying away. Unless they have access to historical records, those astronomers will not know the universe is expanding and will think instead that they are in a static universe. They will be unable to determining the true nature of the universe.[2]
If something is expanding means that we will see it contracting as we “run the movie” in reverse. At some point in its past, the universe must have been extremely hot and dense. This is the main premise of the Big Bang theory, the prevailing cosmological model. In the last years, large particle accelerators have been built to experiment on and test such conditions, resulting in significant confirmation of this theory. In 2003, scientists announced that the “most detailed and precise map yet produced of the universe just after its birth confirms the Big Bang theory in triumphant detail and opens new chapters in the early history of the cosmos.”[3]
The data, which was the result of one year of detailed observations collected by a NASA probe one million miles from Earth, showed a universe 13.7 billion years old, with the first stars shining 300 million years after the Big Bang. More refined observations by the Planck space probe, done in early 2015, added about 80 million years to the universe’s age, putting it at 13.8 billion years old. This showed that the cosmos is expanding a bit slower than originally thought. The observations, however, were perfectly consistent with the Big Bang theory.
In December 2021, NASA successfully launched the James Webb space telescope, a giant leap forward in our quest to understand the universe and our origins. It will provide scientists with a powerful tool to search for light from the first stars and galaxies that formed in the universe after the Big Bang; to study the formation and evolution of galaxies; to understand the formation of stars and planetary systems; and to study planetary systems and the origins of life.
The accumulated, interwoven evidence supporting the Big Bang is so strong, precise, and varied that cosmologists now regard it not as a theory, but as a fact. What remains uncertain are the possible mechanisms that produced the Big Bang. But where does all the matter and energy in the universe come from? As far as we know, there are about one hundred billion stars in the Milky Way, our galaxy. It is estimated that there are one hundred billion galaxies like ours. What is more, all the atoms in the universe, estimated at 1080, are in constant motion. Since things exist and are in motion, does this imply a First Cause or Prime Mover, as Aristotle stipulated?
Not really. The laws of quantum mechanics allow for the constant creation of particles in the vacuum in the form of particle/antiparticle pairs. This could explain in principle the creation of matter in the universe. As it happens, the total kinetic energy of motion is exactly balanced by the “negative” energy of gravity, so the net energy is exactly zero. That is, while kinetic energy tends to keep particles away from each other, gravity tends to keep them together. A system with two distant particles has more energy than a system with two particles close to each other, because you must expend energy to separate them against the gravitational force that is pulling them together. In effect, gravity adds negative energy to the system. In the case of a universe that is approximately uniform in space, one can show that this negative gravitational energy exactly cancels the positive energy represented by the matter.[4]
While we know where the kinetic energy of the universe comes from, it remains to explain the origin of the “rest” energy given by Einstein’s famous equation E = mc2. This energy fuels the stars including our Sun and is responsible for life on Earth. To account for this energy, we need a theory developed in the 1980s that goes by the name of Inflation.
Box 1: Why is There Something Rather Than Nothing? Why there is something rather than nothing is the ultimate existential question. For the religious believers, the preferred answer is that God caused things to exist. The philosopher and mathematician Gottfried Leibniz (1646-1716) thought that the fact that there is something, and not nothing, requires an explanation. The explanation he gave was that God wanted to create a universe, which makes God the simple reason why there is something rather than nothing. However, this is not really an explanation. “To explain why something exists,” writes the philosopher Roy Sorensen in the Stanford Encyclopedia of Philosophy, “we standardly appeal to the existence of something else... For instance, if we answer, ‘There is something because the Universal Designer wanted there to be something', then our explanation takes for granted the existence of the Universal Designer. Someone who poses the question in a comprehensive way will not grant the existence of the Universal Designer as a starting point. If the explanation cannot begin with some entity, then it is hard to see how any explanation is feasible.”1 For some philosophers, the question of existence is unanswerable. According to the philosopher Stephen Law, the question may not even need answering, as it is attempting to answer a question that is outside a spatio-temporal setting, from within a spatio-temporal setting. He compares the question to asking, “what is north of the North Pole?”2 This has not deterred physicists from providing their own answers, most of which rely on quantum mechanics. In a quantum vacuum state, virtual particles and space-time bubbles will spontaneously come into existence, which means there is not really such a thing as an absolute vacuum, or as Nobel Laureate Frank Wilczek put it, “nothing is unstable.”3 However, this answer may account for the existence of matter (and the origin of ours and possibly other universes, see Idea 3), but not the existence of quantum states, space-time, or the universe as a whole. Indeed, where do quantum states come from? Nonetheless, the probabilistic nature of the real world, as revealed by quantum mechanics, suggests that we approach the question of existence from a different perspective. Quantum theory contradicts many of our intuitions, such as that a particle has a definite position and velocity. Similarly, our thinking about existence may be biased by our intuitions. For instance, many feel that whoever asserts the existence of something has the burden of proof. I would argue, however, that the burden of proof is for those who claim that “nothing” is the natural state of things. From quantum mechanics we know that nature is not deterministic, but inherently probabilistic. Consider that “nothing” is just one state of nature, compared to an infinity number of ways in which “something” can exist. Thus, the probability that “nothing” exists is negligible, in fact zero, compared to the probability that “something” exists. Anyway, it is best if I leave the metaphysical speculation to philosophers. 1. https://plato.stanford.edu/entries/nothingness/. Retrieved Mar 28 2022. 2. Stephen Law (2018). Interview series: Why is There ‘Something’ Rather Than ‘Nothing’? (Part 1). Closer to Truth. 3. Carroll, Sean M. (2018). “Why Is There Something, Rather Than Nothing?”. arXiv:1802.02231v2 [physics.hist-ph].
According to this theory, when the universe was less than a trillionth of a trillionth of a second old, it underwent a brief hyper-explosive growth spurt fueled by an anti-gravitational force embedded in space itself. Inflation ties up many of the loose ends of the Big Bang theory, such as why the universe is so big, so homogenous and so flat. All these and other attributes can be explained in one fell swoop by a rapid stretching of space long ago. Following the inflationary period, the universe continues to expand, but at a less rapid rate.
In the inflationary scenario, the mass-energy of matter was produced during that rapid initial inflation. The theory is rather technical so I will not get into details here. According to the theory, some small amount of energy was necessary to trigger inflation, but it is a fluctuation allowed by quantum mechanics. In other words, no violation of energy conservation occurred.
The basic inflationary paradigm is currently accepted by most physicists, as several inflation model predictions have been confirmed by observation. However, a substantial minority of scientists dissent from this position. Many physicists have voiced criticisms, claiming untestable predictions and a lack of serious empirical support. The next step is to find a more direct proof of Inflation theory, which predicts an even fainter pattern of light polarization.[5]
This is a good point to stop and reflect on the evidence presented so far. After all, this book is mainly about ideas, not science. Overwhelmingly, the evidence shows a complex but lawful universe. The birth of the universe, so it seems, did not violate any laws of nature and everything indicates that it has evolved, and will continue to evolve, according to these laws. Of course, the theories have gaps, and they may be changed or dropped altogether as astronomers refine their observations and formulate new hypothesis. This is how science makes progress (see Idea 12, forthcoming).
Nonetheless, there is nothing in the data that supports the claim that the universe has a plan or purpose, or that the universe was created for humans’ sake. We now know that the Earth is not in any particularly privileged position in the universe. Our solar system, once thought to be the center of the galaxy, is in the outer edge of the Milky Way, and in fact anywhere in the cosmos one would also view other galaxies moving away at rapid speeds, just as we see here on Earth.
The emergence of the particles that make “us”
We are all made of atoms; the account of how these atoms emerged from more basic particles and transitioned into the amazing variety of living creatures we observe today, including “us”, is one of the greatest scientific achievements. This is in fact a fascinating story relevant to all of us, not only scientists, and I believe it should be part of our common cultural heritage.
So, where does all the matter that “makes us” come from? Immediately after the Big Bang the universe was dominated by radiation, meaning that most of the energy was in the form of photons and massless particles (like neutrinos) that moved at near the speed of light. As the universe expanded, the temperature dropped and when it reached about one billion degrees Kelvin neutrons combined with protons to form the universe’s deuterium and helium nuclei. This process is called primordial nucleosynthesis.
After about 379,000 years the electrons and nuclei combined into (mostly) hydrogen and helium atoms. Over a long period of time, these atoms condensed and ignited, creating the first stars. Inside the stars, nuclear processes created heavier atoms, such as carbon, oxygen, silicon and iron. This process is known as stellar nucleosynthesis. These stellar atoms were ejected from stars at the end of their lives and became stardust, floating through interstellar space. Most of the atoms that make up the Earth, including us, were probably present in their current form in the nebula that collapsed out of a molecular cloud to form the Solar System.[6] We are all stardust!
It’s amazing to think that the particles and atoms that make up our bodies were created in stars (the byproduct of nuclear reactions). It takes billions of years for a star to produce the carbon and oxygen we use in every breath we take. It is only now, in the last few decades, that we have learned enough to conceptualize the full scale of human genealogy. It is, for me at least, a continuous source of wonder that I can trace my lineage back fourteen billion years or so through generations of stars. The particles and atoms that make up my body and brain floated for billions of years through space to become part of our solar system. After the sun (a third-generation star) and the earth were formed, it took four and a half billion years for intelligent life to emerge. We are all special beings in that it took, literarily, billions of years to make each one of us.
Our planet is also special. It is particularly suitable for life. Life could not have emerged on Earth without the existence of an oxygen-rich atmosphere, which together with the ozone layer and the magnetic field, protects organisms against cosmic radiation and spatial debris. It also helps that our sun is a stable star not too prone to release huge plasma plumes, and that the Earth has an axial tilt stabilized by the moon. Other mechanisms, such as plate tectonics, help to regulate the levels of carbon dioxide and keep the global temperature stable.[7]
To conclude: Treasure your special bond with nature
We are deeply connected with nature, so much so that the boundaries between our autonomous selves and our surroundings are diffuse. The energy from the sun and the water from clouds make it possible for plants to grow and multiply. We consume these plants and other animals that in turn feed from these plants. These nutrients are decomposed and returned to Earth, beginning the cycle anew. There is also an internal “renewal” cycle of sorts, as our body’s cells are constantly replicating, creating their own replacements. Over time, most of the atoms in our bodies are replaced.
The most important lesson to take home is that humans are not above nature, put on Earth to master over “the fish of the sea, the birds of the sky, the cattle, and all the earth,” but we are part of nature; in fact, we are nature. According to the German philosopher Friedrich Schelling, the self and nature are identical. In his naturphilosophie (nature philosophy), he questioned the mechanical models of nature developed by Isaac Newton and other physicists. Instead, he pronounced that everything – from insects to trees, stones to birds, rivers to humans – was part of one great organism. He explained this to his students by pointing to the moment when the self becomes aware of the world around it: “At the first moment, when I am conscious of the external world, the consciousness of my self is there as well,” he said, “and vice versa – at my first moment of self-awareness, the real world rises up before me.”
Instead of dividing the world into mind and matter, as philosophers had done for centuries (see Idea 10, forthcoming), Schelling told his students that everything was one: “As long as I myself am identical with nature,” he insisted, “I understand what living nature is as well as I understand myself.”[8] This was a radical idea that would change the way humans think about themselves and nature.
Today, as we experience the catastrophic effects of climate change, Schelling’s ideas of unity with nature have been imbued with a new and desperate urgency. For decades scientists and activists have tried to convince us with predictions and statistics — but somehow, they do not change our behavior. Most of us understand on an intellectual level what is at stake, but that does not seem to be sufficient. According to the late American paleontologist Stephen J. Gould, we cannot win this battle to save species and environments without forging an emotional bond between ourselves and nature — for we will not fight to save what we do not love. Our future looks bleak unless we “relearn” how to love nature. More on this topic in Idea 18 (forthcoming).
[1]The primary evidence for dark matter comes from calculations showing that many galaxies would behave quite differently if they did not contain a large amount of unseen matter. Some galaxies would not have formed at all and others would not move as they currently do. See “Dark Matter”. CERN Physics, Jan 20, 2012. https://home.cern/science/physics/dark-matter. [2] “The Universe, Expanding Beyond All Understanding,” by Dennis Overbye, The New York Times, June 5, 2007. [3]“For Astronomers, Big Bang Confirmation,” The New York Times, February 12, 2003. [4] A layman account can be found in “For astronomers, Big Bang confirmation,” The New York Times, February 12, 2003. [5] A non-technical explanation of this research can be found in: http://map.gsfc.nasa.gov/universe/bb_cosmo_infl.html. See also Clavin, Whitney (17 March 2014). "NASA Technology Views Birth of the Universe". NASA. [6] Hawley, J. F. & Holcomb, K. A. (2005). Foundations of modern cosmology, Oxford University Press. [7] Gribbin, J. (2011). Alone in the Universe: Why our planet is unique, Wiley. [8]Bowie, A. (2012). Friedrich Wilhelm Joseph von Schelling. In Zalta, Edward N. (ed.). Stanford Encyclopedia of Philosophy. Also, “What a Young Philosopher Discovered More Than 200 Years Ago About Nature,” by Andrea Wulf, The New York Times, Sep 13, 2022.
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