The study of the Universe (cosmology) has changed considerably over time. With every new discovery, our conception of the cosmos has undergone a seismic shift.
Host | Matthew S Williams
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Episode Description
The study of the Universe (cosmology) has changed considerably over time. With every new discovery, our conception of the cosmos has undergone a seismic shift.
If science is like an onion, constantly shedding its skin, then the cosmos is like an onion that grows by orders of magnitude every time it sheds!
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The History of Cosmology
The authors acknowledge that this podcast was recorded on the traditional unseeded lands of the Lekwungen Peoples.
Hello, and welcome back to Stories from Space. I'm your host, Matt Williams.
And today, inspired by recent news from the James Webb Space Telescope and the deployment of the European Space Agency's Euclid telescope, I felt inspired to talk about the subject of cosmology, which basically comes down to the study of the universe as a whole, how it came to be its evolution, its formation, and its ultimate fate.
So this touches on a number of other fields, such as astronomy, astrophysics, astrobiology, it's basically the study of everything. And this is something that human beings have been contemplating for as long as we have existed.
And if we look at how our astrological and astronomical traditions have evolved since ancient times, we can see that with every new major discovery with every new shift in consciousness, our concept of the Universe, our concept of what constitutes the cosmos - it has grown exponentially.
It's now reached the point where the Universe as we know it is so unfathomably huge, possibly even infinite, that it just completely overwhelms the mind. It crushes a person's sense of self to think of how immensely tiny we are in the grand scheme of things.
Another thing that's changed over time is how we perceive these very questions. Where did we come from? Where are we headed? What's it all about? What's it all made up of what governs our universe and the fundamental forces, what is the reason for their existence?
This all used to be considered metaphysics and philosophy, and religion, speculation about our origins and our ultimate fate. But cosmology is interesting that way, because whether you interpret it in terms of metaphysics, whether you interpret it in terms of faith, or religion, or anything for that matter, or as a scientific pursuit, it remains the study of everything: how everything came to be.
And much like our theories on history, and the natural environment, and what governs human interactions, these too, over time, became a matter of cause and effect and a focus on demonstrable, verifiable, calculable factors rather than mystical forces or divine intervention.
If there has been a process when it comes to knowledge in the Universe, it's been moving away from the mythological into the realm of the physical. And here tot though, cosmology really hasn't changed that much.
When one speaks about the Universe, even in the most material, empirical sense, it still brings up all manner of awe and mystery. And there are allegorical similarities to religious fables and metaphysics that are undeniable. So that's what I wanted to get into today.
And as I said, this is inspired by the next-generation astrophysics missions right now that are investigating some of the deepest questions about our existence in the Universe: how it evolved over time, what role the mysterious forces of dark energy and dark matter play in its evolution.
And whether or not the chief aim of these missions and of all these observations is basically to either confirm or correct our fundamental theories of how the universe behaves on the largest scales.
So basically, is Einstein's theory of General Relativity and our current cosmological models for which it is integral, are they wrong? Are they in need of revision? Or do we just need to fill in the missing pieces? That's what these missions are attempting to answer.
So I thought I'd take the time to look at the history of how we've asked and how we've addressed these fundamental questions because it really is fascinating to look at how we got here where we are today.
So to paraphrase something a professor of mine who taught the history of science - as he once said: “Science is like an onion. It's constantly shedding its skin.” It's constantly reinventing itself with every new idea and new discovery.
And in that respect, humanity's concept of the Universe has been similar except, instead of it simply renewing and reinventing itself, it's always gotten bigger over time.
The world as we knew it used to mean our planet or, rather, our small corner of it.It then became the entire planet adrift in a Universe. The Universe of seven astronomical bodies centered on Earth.
Then, our planet became one of several that orbited the Sun. The stars became suns much like our own. We then realized we were all nearly small pinpoints of light in the galaxy. We then discovered that there were other galaxies, thousands, millions, billions, and now trillions.
And we've come to realize that the Universe has had a very long lifespan, that it's evolved considerably in that time, and that it's expanded in all that time it's grown. And that what we can see of it is just a fraction of the entire thing.
Because we live in a relativistic Universe, what we perceive as the edge or the boundary, is actually simply looking back in time. And we can only see so much of what is at the boundary at the periphery.
We can see the Cosmic Microwave Background, the relic radiation leftover from the Big Bang. We are beginning to pierce the veil of what existed shortly thereafter, the cosmic Dark Ages. We are starting to get to the point where we can see the first galaxies and track their evolution.
But we know, based on how rapidly the cosmos has been expanding throughout all this time, that what we see is just the tip of the iceberg, basically.
So to give it the historical treatment, how did we get here?
Now every culture on the planet since time immemorial has had its own cosmological and astronomical traditions. And we're limited in how much we know about our own past as a species, largely because written records are what we have access to.
And, of course, many cultures have been quashed and their traditions, forcibly or inadvertently, lost over time. But what we know about the earliest recorded cosmological traditions, that goes back to ancient Mesopotamia.
Like all other cultures, they observed the passage of the stars and the heavens, they noted patterns which they identified as constellations, they monitored the seasons and the cycles, and they found special meaning to it all.
And some of these traditions are still in use today. And there are modern archaeological theories that say that cave paintings - that these were, in fact, attempts to chart the constellations and monitor their passage over time, that the earliest human settlements were also very interested in marking the stars in the sky and their passage through the Zodiac over the course of years, and that they could even predict well ahead into the future based on these.
But when it comes to detailed accounts of what the ancient people thought, ancient Mesopotamia is where the earliest records are traced to. And in this land, which sits between the Euphrates and Tigris rivers in modern-day Iraq, the people laid down traditions that are still followed to this day.
They charted the passage of the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn. All of the so-called wandering stars or planets that are visible in the night sky using just the naked eye. And they assigned names and divinities, and personalities to these bodies.
And as I said, these are still in use to this day, thanks to cultural transmission. From the ancient Sumerians, the ancient Babylonians picked up these traditions, which they then transmitted to West Asia, the Levant. Egyptian traditions also spread outwards from there, and these were picked up in time by the ancient Greeks, the Romans, and Europeans, who carried them well into the Middle Ages.
Even though our cosmological models expanded considerably since that time and astrology is no longer revered the way it once was, we still retain elements of it in modern-day culture. And to give you a sense of how little things have changed...
In the Babylonian tradition, the Sun was named Utu, or Shamash, and was associated with truth, justice mortality, and was depicted as a brilliant chariot in the sky. And this gave rise to the Greek Helios, the guardian of oaths and sight, who was also riding in a chariot, and the Roman gods Sol Invictus.
Mercury was known as Nabu or Nebo to the Babylonians, which was the god of literacy and reasons, scribes and wisdom, which became the basis for Hermes, the herald of the Olympian gods, and the Roman god Mercury, who was the messenger of the gods.
Venus is known as Inanna, or Ishtar, the goddess of love, fertility, sex, war (even!), and political power. This became the basis for Aphrodite in the Greek pantheon and Venus in the Roman Pantheon; again, associated with love, fertility, and Sex.
Earth, meanwhile, was known as Antu or Ki, and Earth was the mother of the gods and the sister and consort to the god of the sky, Anu. And this became the basis for the Greek mother goddess Gaia and also became the basis for Terra (Earth), or Juno in the Roman pantheon.
The Moon was known as Nannar or Sin to the Babylonians. The god of the Moon was associated with wisdom, the totality of divine power, and was also depicted as a chariot rider in the sky. Greeks and Romans retain this as well in the form of Celine and Luna.
Mars was known as Nergal and was the god of war, plagues, strife, forest fires, and all kinds of calamities. And this became the basis for Ares and Mars, the Greek and Roman gods of war too.
Jupiter was known as Amarutuk or Marduk, who was the chief of the gods. And this “father of the gods” idea, it became the basis for Zeus, who was the king of the Olympian gods. And Jupiter in the Roman Pantheon was also known as Jove and was also the father of the modern gods.
And last, Saturn was known as Ninurta, or Ninib, which was a warrior god, the god of agriculture, and the patron god of farmers. And this was reflected in the Greek pantheon, where Kronos, the father of the Titans and Zeus, was also the God of the harvest. And in the Roman Pantheon, Saturn was the Roman god of agriculture.
So even though the names changed over the course of thousands of years, the basic idea was the same. And much the same is true of the 12 constellations that are central to Western astrology: Aries, Taurus, Gemini cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.
The associations have changed slightly, but in many cases, the animals that they're associated with, the symbols they're associated with, have not changed, or at least they haven't changed much.
And so between this point from the ancient Mesopotamians or ancient Sumerians, on down through the Babylonians, the Akkadians, the Greeks and the Romans, and medieval astronomers and astrologers.
The concept of the cosmos being Earth, surrounded by all these other celestial bodies with the Sun and the moon included, revolving around us with an outer firmament characterized by stars and nebulous clouds - this endured for thousands of years.
By the time of the ancient Greeks, these observations were refined, there were predictions and cycles that were being tracked and monitored for each planet. And, of course, it was understood at this point that planet Earth was, in fact, a sphere.
So these other planets also became spheres. The Sun and the Moon provided a great deal of inspiration for this. They appear as large perfect orbs in the sky, they shine, they seem crystalline by Earthbound observers.
And so by classical antiquity, astronomers believed that this applied to all the celestial spheres, to Mercury, to Venus, to Mars, all the way out to Saturn and that these - like the Sun and the Moon - were perfectly shaped spherical bodies that orbited Earth in concentric, perfect circles, one inside the other.
Now, an interesting thing is that before Socrates, before Plato and Aristotle, pre-Socratic Hellenistic philosophers, philosophers of Greece and its many colonies and offshoots, they toyed with the idea that, in fact, the Earth wasn't at the center of the Universe, that there was no common center, or that the Sun itself might be the center of all things.
And this was evident within the writings of Pythagoras and also post-Socratic philosophers, people like Seleucus of Seleucia. However, the idea of heliocentrism would not be synthesized and arises its own complete system until the time of the Scientific Revolution. In the meantime, the geocentric model would remain accepted canon.
In particular, Ptolemy’s Almagest is a seminal volume, written in the second century CE, which contained all the then-known Constellations and records on the brightest stars in the night sky.
And, of course, his geocentric model of the universe, which contained epicycles and equines to explain all the observations noted by ancient Greek astronomers - which we covered in a previous podcast that looked at Copernicus and the Copernican revolution. And, as I said, this would remain canon for European, and Islamic, and Indian astronomers for over 1000 years.
Another major contribution to cosmology, which emerged throughout the same period, had to do with the concept of finite time. And this is a concept that appears in the Abrahamic faiths, which is to say, Judaism, Christianity, and Islam, and was transmitted between these religions. And it is entirely possible that Judaism itself picked this concept up from Zoroastrianism.
Because Zoroastrian religion, which emerged in ancient Persia, there was a period of transmission between the ancient Persian Empire and the ancient Hebrews, which occurred around the time of the Babylonian Captivity and the conquest of Babylon by the Persian Empire, under Cyrus the Great. And it is within Zoroastrianism that the earliest recorded example, to the best of my knowledge, of the Day of Judgment is to be found.
And so this concept of time as a linear thing between a creation event in which God created the world and all life within it, and the end of days when God will judge everyone and determine who goes to heaven, who goes to hell, who is rewarded with eternal bliss and eternal damnation. This went on to become a permanent feature in Western cosmology, and it's still there to this day.
And another major development that happened during Classical Antiquity was the concept that nature was composed of certain elements, or eventually atomism as a philosophy.
And the first recorded Western example of this was in the fifth century BCE, when Greek philosopher Empedocles proposed that the Universe was constituted of four elements - that would be wood, water, fire, and Earth.
And this is similar to Chinese cosmologists who believed that the Universe was composed of five elements: wood, water, fire, earth, and metal, and that the heavens were similarly (like Earth) divided into these different elements.
And roughly a century later, Democritus became the first Western philosopher to argue that the Universe was in fact composed of indivisible particles, which were named atoms, which is derived from the ancient Greek word atomos, which means uncuttable or indivisible.
And there were many Eastern philosophers who propose something very similar that the universe was composed of basic particles, basic elements that matter and energy, in fact, were even interchangeable.
And from the descriptions, they sounded largely spiritual and metaphysical in nature, but nevertheless, they laid the groundwork for atomic theory, and in many ways, predicted advancements that would come in the sciences later in terms of physics and chemistry.
So between the ancient world, Classical Antiquity, and right on up to the Middle Ages, there was a considerable amount of continuity.
By the time of the Middle Ages, astrologers were still using traditions that could be traced all the way back to the Babylonians and Sumerians. But their concept of the universe had grown considerably from those days.
Instead of seeing the world as a ziggurat, or a flat Earth scenario, they came to understand that the Earth was a sphere, and that the moving stars were, in fact, planets, also spheres. And whereas the planets had been associated with various deities in the past, Western cosmology had come to be defined largely by the Abrahamic faiths, the concept of a transcendent God, who had created the cosmos and had divided it between the heaven and the earth.
And whereas the heavens were perfect, Earth was base matter. And all of existence was finite in nature, there was a beginning, and there's an end to it. And Hindu cosmologists came up with a much more complex vision of this they believe that time extended forwards and backwards for trillions of years and that reincarnation was also true of the cosmos itself.
Between European astronomers, Islamic astronomers, and Indian astronomers, the geocentric model would remain the predominant vision of things as defined by Ptolemy. But this was about to change, and the Universe was, once again, about to become a much bigger place.
As the Middle Ages gave way to the Renaissance and Scientific Revolution, he recorded observations of the heavens over the course of 1000s of years, began to give rise to some serious questions regarding geocentrism and the Ptolemaic model because astronomers could not help but notice that the math didn't add up and alternate explanations that had been toyed with for quite some time began to make more and more sense.
And in the Islamic world and among Indian astronomers, a key issue that was raised was whether or not the Earth rotated, which would explain the appearance of the firmament of the stars and the starry sphere and how quickly it rotated through the night sky.
Many even toyed with the idea that the Earth was not the center of the universe, that the universe may be partially heliocentric with Earth revolving around the Sun and the other planets revolving around the Earth, or that the universe had no center.
And by the 15th and 16th century, Nicholas Copernicus, he managed to synthesize all of this information and all of this Classical and Medieval research into a single system. And a major consequence of Copernicus's system was that the Universe was much larger than previously thought.
Because as he stated in his treatise, the rotation of the Earth was responsible for the appearance of the background stars passing through the heavens. The fact that the Earth orbited the Sun and led to no apparent change in the distance of the stars meant that the stars had to be very far away. And this was the reason why parallax measurements, attempts to measure the distance of the stars by comparing measurements made in different locations, never succeeded.
And this would be refined by Galileo, Kepler, and Newton, who introduced telescopic observations and helped resolve questions of distance and appearance. And as well, Kepler introducing the notion of elliptical orbits, because even Copernicus and Galileo still believed that the planets orbited around the Sun in perfect concentric circles. And then Newton who provided a unified theory of gravity and how it governed all objects in the known universe. This finalized the heliocentric model and gave rise to the modern view of the solar system.
In addition, Galileo made another very interesting discovery while conducting his observations of the solar system. In his treatise, Sagittarius Nuncius, or the Starry Messenger, he used his telescope to look out at the Milky Way.
So for thousands of years, astronomers have been looking at the Milky Way, and they perceived it as being this nebulous cloud that streaked across the sky, and received the name the Milky Way for this reason.
When Galileo observed them, however, he discerned stars, and he wrote in Siderius Nuncius that this nebula was, in fact,stars densely packed together. And this too, along with what Copernicus had said about parallax measurements of the distant stars, indicated that the Universe was far bigger than anyone had thought.
Now this thread of thought would be picked up later in the 18th century by Immanuel Kant and William Herschel, who also conducted observations of the night sky and looked at the Milky Way, and attempted to discern what it was.
Like Galileo, Kant proposed that it was a large collection of stars that were held together by mutual gravitational attraction, borrowing from Newton. And as he described it, he theorized that, like the solar system, it rotated around a common center, and that it flattened out into a disk. He further speculated that other nebulous clouds that could be seen in the night sky separate from the Milky Way, we're, in fact, other galaxies and not clouds of gas.
In 1785, William Herschel took this a step further and attempted to map out the shape of the Milky Way. And this was painstaking work and consisted of him counting the stars and positioning them relative to Earth throughout the night sky. And from all this, he derived a very interesting illustration of what the Milky Way looked like.
It did not look like a disc at all or the common fried egg profile that we're familiar with today. It looked much more like a leaf or some kind of elongated aquatic creature, which had a front end that looked almost like a tentacled face and a rear section that looked like a tail - two large fins. And the Sun, he believed was directly in the center of this. So he plotted it there on this map.
And the next revolutions, they didn't really come until about the 20th century. In 1900-1901, Dutch astronomer Jacobus Kapteyn created another map of the Milky Way. And instead of relying on simply his own observations, he relied on astronomers worldwide to share photographs of different regions of the night sky. And based on the apparent brightness of the stars in the photos, plus detailed research about their velocities, he was able to construct a much higher precision map that began to visualize the galaxy as a large circular object with much more accurate estimates of distance in space between objects.
But, by far, the greatest cosmological revolution of the early 20th century came from Albert Einstein. And it was between 1905 and 1916 that Albert Einstein began to publish his Theory of Relativity, which led to a complete rethink and reinterpretation of gravity and how it behaved on the largest scales.
And also reconciled Newtonian mechanics and what we knew about velocity and motion in our Universe with another revolutionary and emerging field of study, which was electromagnetism, which would lead to the birth of quantum physics. Once again, a new era of cosmology was about to dawn. And once again, the Universe was going to get a lot bigger.
By the end of the 20th century, several revolutions would happen, each of which would cause a seismic shift in our understanding of the universe and our place in it. We'll examine what those revolutionary discoveries were in part two of our look at the history of cosmology. Thank you for listening. I'm Matt Williams, and this has been Stories from Space