“Everybody has a little bit of the sun and moon in them… Everyone is part of a connected cosmic system. Part earth and sea, wind and fire, with some salt and dust swimming in them”
Suzy Kassem
Mankind has always possessed a deep curiosity about the ultimate existential questions of life: how is it that the world came to be and what forces in it led to my creation? Our ancestors, lacking scientific knowledge, made up supernatural creation stories to help them answer these questions and to explain the natural world that their limited human senses observed all around them.
Those of us living today are fortunate because we are on the threshold of becoming the 1st generation to ever know in great detail, and with some confidence, the answers to those great questions. In the past decade the results of several major observational studies have brought a level of clarity and coherence to our understanding of the universe that we have never had before.
The pace of recent cosmological discoveries has been truly breathtaking; especially considering that it was less than 500 years ago when man first learned that the earth revolved around the sun and less than 100 years ago when astronomer Edwin Hubble proved that the universe actually contained more than 1 galaxy.
Thanks to images taken by the Hubble Telescope over the last 30 years; and the first astonishing images produced by the recently launched James Webb Telescope – which sits a million miles away in space – astronomers now have the capability of looking back to the beginning of time – to see the actual birth of galaxies.
The Webb Telescope is 100 times more powerful than the Hubble, with six times more light collecting capability, enabling it to see objects in much finer detail. The increased clarity of the new images have led astronomers to increase their estimates of the number of galaxies in our universe from 200 billion to 2 trillion!
What really sets the Webb Telescope apart is its ability to focus on the infrared portion of the light spectrum. Most telescopes are designed to see only the small sliver of visible light emitted by stars. The problem with the visible light spectrum is that it gets blocked by the abundant amount of dust and gas that is floating around the universe.
Infrared light is invisible to the human eye but makes up much of the light that comes our way from the universe. The infrared spectrum of light can see past all that dust and gas, which allows astronomers to look with unprecedented detail at some of the earliest and faintest celestial objects in the universe, ones that were born over 13 billion years ago.
Another incredible capability of the space telescope is its ability to detect exoplanets. An exoplanet is simply a planet that orbits a star outside our solar system. Exoplanets have been historically difficult to find because they are very far away, do not emit any light, and are typically much smaller than the stars they orbit.
But astronomers have discovered innovative indirect methods to detect these exoplanets by measuring the dimming of the light of a star that occurs as a planet passes in front of it or by monitoring the spectrum of a star for the tell-tale signs of a planet’s gravity pulling on it and causing its light to subtly Doppler shift.
Using these planet detection methods, astronomers have estimated that about 1 in 5 “sun-like” stars in the Milky Way Galaxy have an earth-sized planet located within its habitable zone. This would calculate to more than 11 billion potentially habitable Earth-sized planets in our own galaxy to discover!
Incredible as it may seem, Astronomers can detect not only the presence of an exoplanet, they can also employ powerful scientific instruments on the telescope, called spectrographs, to identify the unique signatures of specific molecules in their atmosphere.
When an exoplanet passes in front of its host star, a small fraction of the stellar light passes through the exoplanetary atmosphere, where different molecules absorb light of some wavelengths while light of other wavelengths can pass through unhindered. By measuring the fraction of stellar light able to penetrate the atmosphere at different wavelengths, the chemical composition of the atmosphere can be determined.
Turning the intensity of light measured at different wavelengths into graphical signatures allows scientists to measure the chemistry in the atmosphere of distant planets and detect the presence of water or methane molecules which, if found, could provide evidence that there is – or once was – life on the planet.
I had a passing interest in star gazing when I was a boy. I would set up my cheap telescope in my back yard and focus on different celestial objects, not really knowing what I was looking at. My interest in astronomy faded over time as I became busy with the business of life. After my retirement, however, I decided to pick up my old hobby by signing up for one of the science classes produced by the Great Courses called Cosmology: The History and Nature of our Universe. The course re-kindled my interest in the cosmos and stoked my imagination about the wonders of the universe.
Here are just a few of the the things the course covered that seem incredible to me and filled me with wonder:
We can travel back in time…
Even though Albert Einstein’s theory of relativity tells us that nothing can travel faster than the speed of light, the universe is so vast it still takes light from distant galaxies a long time to reach the earth. By observing light that originated far away we are travelling back in time to see how the Universe looked when it was younger (we can’t know for sure what distant objects in the universe look like today because their light is not yet observable to us).
Light travels at a speed of 186,282 miles per second, which equates to 5.88 trillion miles per year – which scientists define as the distance light travels in 1 light year. Light from any celestial object that is more than 5.88 trillion miles away from the earth takes more than 1 earth year to reach us. Earth’s average distance from our sun is 93 million miles, so its light only takes about 8.3 minutes to reach us.
The telescopes we have today are powerful enough to observe the first light that came from the hot glowing gas of the Big Bang itself, that moment in time approximately 14 billion years ago, when astronomers believe that our universe came into being.
The brilliant light from this hot gas is observable to scientists via what is called the cosmic microwave background and it shows astronomers a view of the Universe approximately 400,000 years after the Big Bang. Immediately after the Big Bang, the Universe was so hot that the gas was foggy and impenetrable, but as time passed expansion cooled the Universe, and after 400,000 years the temperature dropped enough for the fog to clear and for atoms to form.
So, looking outward (and back in time), our vision is limited by this bright, glowing wall of fog. As the light crosses the expanding Universe, its waves are stretched 1000-fold and arrive as microwaves. So the microwave background reveals the universe in its “pre-embryonic” state right after the Big Bang!
The Laws of the Universe are constant…
Einstein once famously said “The most incomprehensible thing about the Universe is that it is comprehensible.” How is it possible that humans could have developed the mental capacity to understand such a vast and utterly remote cosmic realm? How can something that emerged out of the atoms and evolutionary forces of Nature come to comprehend itself?
The answer is that we all are, in a sense, children of Nature. Much of the character of the universe is all around us here on earth. We’ve evolved in an astronomical setting that is itself beholden to the same laws of physics that span all of space and time. The laws of physics are the same everywhere, and there is much that is cosmic even here on Earth. For example, humans have evolved within Newtonian space and time, which is identical to 99% of cosmic space and time, and this has resulted in our ability to comprehend things like location, distance, size, light and speed.
As far as we know all objects in the universe obey the same universal laws of nature (gravity, motion, thermodynamics, electricity, energy). Because we have studied these topics here on earth for centuries, we can apply our understanding of these laws to everything we observe in the universe.
The nature of matter is constant…
Not only are the laws of physics the same throughout the universe, so is the nature of matter. As far as we know the atomic elements that make up all the matter on earth exists everywhere throughout the universe.
Us, and everything around us, are made of atoms. Atoms are incredibly tiny and numerous. There are about 100 kinds of atoms that we have discovered, each making a particular chemical element, such as hydrogen, carbon, gold, or uranium. The elements are ordered in a periodic table so that elements with similar chemical properties line up in columns.
The Thermonuclear fusion occurring inside stars causes them to become “atom factories.” The huge weight of a star makes a hot, dense core like a furnace: The star burns lightweight fuels into heavier ones. This fusion burning releases energy, which heats the core further and keeps the reactions going. Heat also moves up to the surface, which glows brightly. In the core, the ash from one reaction becomes the fuel for another.
For example, hydrogen burns to helium, which then burns to carbon, and so on. Reactions further down the sequence need ever-higher temperature, because nuclei with more protons repel more strongly. Ultimately, how far along this sequence a star gets depends on its mass; stars of higher mass
can make heavier elements.
How do these freshly made nuclei get out of the star’s core and into the matter that makes up our universe? The remarkable journey starts when the nuclei are brought to the surface in huge, hot currents of gas. On their way up, at lower temperature, the nuclei acquire their quota of electrons and become atoms. These atoms are finally ejected into space when the fuel runs out, the nuclear reactions cease and the star dies.
We are made of star stuff…
When the astronomer Carl Sagan said his famous line that each of us are made of star stuff, he was reminding people that much of the matter of our bodies was created within the stars long ago. He wanted people to know we are marvelous and our story is, too.
Modern cosmology doesn’t just deal with huge things like stars and galaxies; it must also consider the creation of atoms and the planets and people that atoms make. It is a story that takes us from the hearts of atoms to the hearts of stars, and out into the galaxy to watch the birth and death of stars and planets.
It is complemented by the the billion-year mechanism that slowly coaxes these tiny atoms into assembling plants and animals and people – and even the brain reading this sentence. We are no less a part of the Universe than any star or galaxy.
The atoms in you and me probably drifted around in the interstellar medium for 1 or 2 billion years before joining a denser cloud. Within such clouds, small pockets collapse to form stars, and around these stars, disks of dust and gas, which in turn form planets.
In the case of the Earth, some atoms ended up in a spherical ball, with a barren, cratered surface heaving with volcanism. During the next 4.5 billion years, an extraordinary transformation took place, enabled by atoms’ amazing ability to stick together and form molecules which can combine in complex ways.
It’s easy to feel small and insignificant when you consider the vastness of the universe and the timescale of celestial events, especially in comparison with our meager human lifespan. We become awestruck while looking at telescopic images and realizing that a single picture representing one minuscule sliver of the universe is filled with thousands of galaxies, each with billions or trillions of star systems and each of those with its own planets.
Deep field images like those produced by the Webb telescope show us spectacular moments frozen in time. We can see galaxies wrap around one another, colliding and tearing their dusty, star-riddled arms apart in a violent ballet. It’s no wonder that people all over the world stare in wonder at the majesty of it all.
Space exploration is one of the few things that our divided society can agree is overwhelmingly positive. It reminds us of our inherent connection with the universe, but it can also lead to feelings of a profound sense of insignificance – showing us, on a grand scale, just how small we are.
However, despite the vastness of the Universe and our small place in it, we should not feel insignificant. A diagram plotting mass versus complexity would show that living things are enormously more complex than astronomical objects. If objects shone with a brightness in proportion to their complexity, then galaxies would be dim light bulbs, while our brain alone would be a beacon of light visible across the whole Universe!
When you think about it that way, we are very special – and we should be grateful to the stars above that we are one of the most complex things the universe has ever made!
Words to Live By... 