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Somewhere in the middle between the size of our vast universe and a tiny neutrino are human beings.
We do not know the exact size of the universe. We know it is massive. The farthest we have seen so far is 46.5 billion light years in any one direction, which makes the width of the observable universe some 93 billion light years across, an area that contains an estimated 170 billion galaxies. But astronomers believe there is more out there that is so far away and moving so fast away from us that we may never see it. It is speculated that the entire universe could be as much as 200 billion light years wide and contain a trillion galaxies. A few scientists are beginning to think that the universe may actually be infinite.
At the opposite end of the scale is the neutrino, a tiny, almost massless, electrically neutral particle given off in trillions by stars such as our sun and especially by exploding supernovae. They are so small that thousands of them so go right through the Earth and our bodies every second and whizz right by the protons, neutrons, and electrons in all of our atoms.
Millions of dollars have been spent on elaborate equipment that enable scientists to detect and study these elusive sub-atomic particles. There existence was predicted by Wolfgang Pauli in 1930, and the then theoretical particle was named by Italian physicist Edoardo Amaldi in 1932 in conversation with Enrico Fermi. The word neutrino means little neutral one in Italian.
It took 36 years for scientists to finally detect the tiny particle. In 1956 Fred Reines and Clyde Cowan working at the Savannah River National Laboratory in South Carolina detected neutrinos, and in 1995 Reines received the Nobel Prize in physics for the discovery. Cowan had died in 1974.
Since 1956 several neutrino detectors have been built around the world and many neutrinos have been detected. Currently, one of the largest detectors is the Deep Underground Neutrino Experiment or DUNE being constructed at Fermilab near Chicago. One of the goals of the experiment is to determine if neutrinos could give us clues to the nature of Dark Matter and Dark Energy which together make up some 95% of the universe. Ordinary matter, such as stars, planets, and humans make up only 5% of the universe.
One of the tiniest particles that has mass as well as a small electrical charge is the quark. The nucleus of every atom except hydrogen is made of protons and neutrons. The basic hydrogen atom, has 1 proton and 1 electron and no neutron. Every proton and neutron in turn is made of ‘up’ quarks with a 2/3 positive charge and ‘down’ quarks with a 1/3 negative charge. Combining 2 up quarks with 1 down quark produces a positively charged proton. Combining 2 down quarks with 1 up quark produces a neutral neutron. Each set of 3 quarks in protons and neutrons is held together by particles appropriately called gluons that create force fields strong enough to hold the quarks together.
Quarks were discovered in the mid-1960s by two physicists working independently, Murry Gell-Mann and George Zweig. Gell-Mann named the tiny particles ‘quarks’ after a passage in James Joyce’s somewhat abstruse book Finnegan’s Wake that reads: “Three quarks for muster Mark, sure he hasn’t much of a bark, and sure any he has it’s all besides the mark.” Gell-Mann received the Nobel Prize in 1969 for this and other discoveries.
Physicist Max Planck is credited with helping to get us thinking about the quantum world that is many times smaller than the classical or macro world that all of us grow up with. Quantum refers to the micro world of subatomic particles such as electrons, photons, quarks and other types of matter that we are all made of but that seems to move in a different realm of reality.
For example, Planck came up with quantum level measurements that are so small they do not make sense to anyone measuring a standard wooden board or checking the time of day. The Planck Length, for example, is 1.6 times 10 to the minus 35 meters. This is smaller than a proton, electron, or even a neutrino. This distance seems to have no practical use except in some physics calculations. Some scientist speculate that it might be comparable to the length of a ‘string’ in string theory.
Planck also came up with a measurement of time that is ridiculously small: the Planck Time. It is 10 to the minus 43 seconds or the time it takes a photon to travel the distance of the Planck length. There is also the Planck Constant that expresses the relationship between the energy of a photon and its frequency. We know, for example, that high frequency gamma ray photons are more energetic than radio waves and the Planck Constant helps us determine that difference.
Planck’s work helped set the basis for modern day physics, that is, how to understand the movement and energy of sub atomic particles that everything in the universe is made of. These measurements seem to have little effect on us in our day-to-day macro world. But neither do neutrinos, and yet we know they are there.
About the time in the late 1800s and early 1900s when Max Planck was working out his measurements, other physicists were working on the tiny electron, the negatively charged particle orbiting the much larger nucleus in an atom. The electron was discovered in 1897 by John Joseph Thompson. A few years later, in 1909, Robert Milliken established that the electron had a negative charge that could be measured.
Thus, the concept of the electron volt came into use as a way to measure the electrical energy not only of an electron but other subatomic particles such as photons. The electron volt is defined as the amount of energy that an electron acquires when it moves through a potential difference of one volt. Put mathematically it is written 1 eV = 1.6 X 10 to the minus 19 joules, with joules being units of work energy. Electron voltage is used extensively in determining the energy of wavelengths of electromagnetic frequencies.
Electrons are tiny and numerous. To put the size of an electron into perspective, in a conductive wire when 1 ampere is flowing through it, there are 6.2415 X 10 to the 18 electrons flowing by every second. Electron flow keeps the lights on and the computers computing. At the bottom of all matter, everything is electric.
On the other end if the size spectrum, one of the largest things seen so far in the universe is the Hercules Corona Borealis Great Wall, a cluster of billions of galaxies about 10 million light years across and roughly 10 billion light years away from Earth. Discovered in 2013, it is found in the direction of the constellations Draco and Hercules in the vicinity of Polaris, our current pole star. One can only speculate about how many stars and planets are in the Great Wall.
Back on Earth, the smallest semi-living things we encounter are viruses which are only about 20 nanometers or 20 billionths of a meter in diameter. Not all viruses are bad for humans, but some are, including our current least favorite virus, the Covid virus that keeps lingering among us. Viruses contain DNA but are not capable of using it for replication or metabolizing nutrients until they invade a host cell and use that cell’s nucleic acids, as well as its mitochondria and other organelles in order to get the nutrients and energy it needs to be able to replicate. Once a virus invades a cell, it can make multiple copies of itself which then invade other cells.
Although viruses are extremely small, the sheer number of them can make them a major health hazard. Within a few hours of infecting a cell and spreading to other cells, billions of virions can get into the bloodstream in a process called viremia and travel to other parts of the body and infect many other cells. Found in all living things, it is estimated that there are many times more viruses on Earth than the total of all the stars in the known universe.
The largest thing we see around us and that we are part of is our home galaxy, the Milky Way, a barred spiral galaxy thought to be about 130,000 light years across and containing an estimated 200 billion stars. Our solar system is located in one of the galaxy’s spiral arms and circles the massive black hole at the center of the galaxy every 230 million years. To put our planet’s location in perspective, if we traveled from Earth to the center of the Milky Way in a rocket ship going the speed of light, or almost 671 million miles per hour, it would take us about 25,000 years to get there.
The thing that keeps us alive, our sun, is over 864,000 miles in diameter which is 109 times that of Earth’s 7926 miles in diameter at the equator. The sun is considered a medium sized star with some stars in our galaxy smaller and some much bigger. In a process called stellar nucleosynthesis, the sun fuses hydrogen into helium at the rate of 600 million tons of hydrogen per second. That is a lot of hydrogen, but scientists believe there is enough hydrogen in the sun to keep it going for another 5 billion years. As big as the sun is, it is dwarfed by the largest star found in the Milky Way so far, a star called UY Scuti located in the Scutum constellation. It is approximately 1.477 billion miles in diameter.
Our Milky Way is big, but it is a good bit smaller than our nearest neighbor galaxy, Andromeda, which is some 220,000 light years across and believed to contain up to one trillion stars. But even Andromeda is only of average size compared with some other galaxies in the universe. For a few years astronomers considered galaxy IC 1101 at 4 million light years across to be the largest of the 200 billion galaxies in the universe. But recently there has been an even larger galaxy discovered. It is called Alcyoneus, and at 16 million light years across, it is the largest found so far. Our Earth keeps getting smaller and smaller.
Returning to Earth again, the smallest organism capable of growth and reproduction on its own is a tiny parasitic, sexually transmitted single celled bacterium called mycoplasma genitalium. At only 250 nanometers in length, and containing only 525 genes in its DNA, it is considered one of the smallest truly living things on Earth. In spite of its tiny size, however, upon taking up residence in a person’s urinary and genitalia tract, it can cause serious infection and urethritis.
At about one millimeter in diameter, still very tiny but moving up the evolutionary ladder to multicellular life, is the Trichoplax adhaerens, a marine dweller that is considered to be the simplest multicellular animal discovered so far. It is balloon-like in shape with no front or back, yet with its few hundred cells, it is capable of random movement and can absorb food particles such as tiny microbes.
Whereas mycoplasma genitalium is an unnecessary parasite, life on Earth could not exist without another microscopic substance, deoxyribonucleic acid or DNA. It is found in every cell, both plant and animal, on Earth. Each human body’s approximately 30 to 40 trillion cells contain 3.2 billion base pairs of DNA, which is coiled up into a ball 6 microns, or 6000 nanometers, in diameter. If straightened out, however, each DNA strand would be over 6 feet long. Multiplying 6 feet times 30 trillion cells, you can see that each one of us contains many millions of miles of DNA. Every cell in every living thing, and even viruses which must enter a living cell to become alive, has DNA to guide its growth and control what it becomes. Our DNA and our cells are truly remarkable living storage units.
A size comparison that is quite an interesting coincidence is the relationship of the sun and moon during a total solar eclipse. The sun is 93 million miles away from us and approximately 864,000 miles in diameter. The moon with its elliptical orbit around Earth averages some 238,855 miles from us and is only 2,158 miles in diameter. Despite these size and distance differences, during a solar eclipse when the moon lines up directly in front of the sun, the two appear to be exactly the same size.
This is obviously a case of we modern humans being at the right place at the right time. Since its formation over 4 billion years ago when Earth collided with another planet, the moon has been moving away from us at the rate of 1.48 inches per year. We do not perceive this movement during a human lifetime, but over millions of years, the distance adds up to thousands of miles. So, a few million years ago during a solar eclipse when the moon passed in front of the sun, the moon would have been closer to us and would have appeared larger relative to the sun. A few million years into the future, the moon will be farther away and appear smaller and not fully cover the sun. Our ancient ancestors did not see a solar eclipse as we do, nor will our distant descendants see the sun and moon appear to be the same size during an eclipse as we do today.
At the end of a busy day, most of us enjoy sitting on our porch or patio with a glass of iced tea and relax. We like to sit still a few minutes and let the world go by while we reenergize ourselves. But are we really sitting still? If we knew how fast we moving we would spill our tea.
To start with, the Earth turns on its axis at a speed of 1040 miles per hour. At that speed, if we did not have gravity holding us down, we would fly off into space from the centrifugal force on our bodies. Even faster is the speed at which Earth orbits around the sun which is 19 miles per second or 67,000 miles per hour. That speed with an orbit distance of 584 million miles gives us our sideral year, that is, a full orbit of 365 days, 6 hours, 9 minutes, and 9.76 seconds with respect to the fixed stars.
67,000 miles in one hour is fast, but hold on to your hat. We’re just getting started. Our entire solar system revolves around the enormous black hole at the center of the Milky Way, and we are traveling with it. The 230 million years it takes Earth to circumnavigate the galaxy center gives us an orbit speed of approximately 514,000 miles per hour. And on top of that, the entire Milky Way galaxy is traveling at a rate of 1,296,000 miles per hour along with a group of about 100,000 other galaxies in a cluster some 520 light years across called the Laniakea Supercluster. Even sitting still, you are traveling thousands of times faster than the fastest manmade rocket so far sent into space. Are you dizzy yet?
Along with its 200 billion stars, the Milky Way is home to some of the largest bubbles found in the observable universe. Spewing out 25,000 light years above and 25,000 light years below the center of the Milky Way are extremely large bubbles of gamma rays and X-rays. Called Fermi Bubbles, they are named after the Italian-American scientist who led the team of physicists who produced the first atomic reaction in December 1942.
Astronomers are still speculating as to how and why these huge bubbles formed. Since they are made of gamma and X- rays which are much higher frequency than the human eye can see, they were not discovered until 2010 when satellites were sent into orbit that could detect these frequencies. This situation is a good example of how our technology is helping us discover new and surprising things about our universe.
Since the Big Bang 13.8 billion years ago, all of the matter in the universe has been expanding. And as Edwin Hubble discovered in 1929, the universe is expanding at near the speed of light. We certainly don’t feel it, but we Earthlings are traveling right along with it. There is a lot of debate these days about what will happen to the universe. Will it keep expanding forever until the stars burn out and everything freezes? Or will it reach a point where gravity begins to pull everything back to another singularity which explodes into a new universe. None of us will be around to see any of this, but maybe a few of our descendants will.
So, from the rotation of the Earth to the movement of our galaxy, to the expansion of everything in the universe, we are moving at speeds that would easily kill us if we did not have the good Earth’s gravity to hold us steady. Pick up your pencil and let it fall. In the time it takes that pencil to fall to the floor, we have traveled several thousand miles. If the pencil floated up instead of falling down, we probably would not be here to discuss the matter.
Some of the distances and times we have discussed here are mind boggling, yet from the quantum to the galactic, they are the reality we live with. The numbers can get daunting. In an attempt to keep the long numbers somewhat under control, physicists and astronomers have come up with a few shortcuts. For example, when measuring distances in our solar system, instead of miles we use astronomical units, AU or au. One au is the distance from Earth to the sun, 93 million miles. Instead of 37,200,000 miles from the sun, Mercury is .4 au. Mars is 1.5 au, Jupiter is 5.2 au, and Neptune is 2.8 billion miles or 30 au from the sun.
When measuring space beyond the solar system, the distances are so great that even the number of light years can become cumbersome. To help alleviate the space distance problem, in 1913 astronomer Herbert Turner Hall using trigonometry and parallax came up with another system of measurement that makes use of the movement of the Earth and its location at different times of the year in relation to distant stars. He called the unit of measurement the parsec, short for parallax of one arc second. A parsec is about 3.26 light years or roughly 19.2 trillion miles. Whereas our sun is a little over 8 light seconds away from us, the next nearest star, Proxima Centauri is 4.2 light years or 1.3 parsecs from us. Polaris, the current North Star, is approximately 433 light years away or 133 parsecs. Using parsecs helps keep the numbers smaller.
Some people consider one of the most interesting coincidences to be the uncanny resemblance of the cosmic web of filaments connecting the billions of galaxies in the universe compared with the microscopic array of filaments connecting the approximately 86 billion neurons in the brain of each one of us. The enormous cosmic filaments, which added together make the largest known structure in the universe, are made of strands of mostly hydrogen gas, and dark matter. Stretching between clusters of galaxies, some of them are megaparsecs in length. Most of the filaments in the brain, however, the axons, synapses, and dendrites that carry electrochemical impulses from one neuron to another, are only a few microns long.
Yet, in spite of the vast difference in size of these two arrays of filaments, when viewed at certain magnifications, the pattern of filaments is so similar it is difficult to tell which are filaments stretching across the universe and which are the tiny filaments carrying information throughout the human brain. One set of filaments connects the structures of space and aids in the formation and evolution of galaxies, stars, and planets, while the other carries the chemical and electrical information that keeps our bodies functioning and our minds thinking.
So, here we are. Thinking, loving, hating, creative, destructive, evolving, curious creatures somewhere in the middle between the massive and the tiny, moving at speeds and distances our consciousness can barely comprehend. But as mind boggling as it all seems, take heart. As Albert Einstein famously said in the 1930s: “The most incomprehensible thing about the universe is that we can comprehend it.”
There are enough wonderous things in us and around us from the workings of our brains, to elusive neutrinos, to the beginning of life, to the expanding universe, to the numerous other phenomena we seek to understand to keep our human minds occupied for many years to come. We make new discoveries every day. Life is exciting. Inquisitive minds will never be bored.
Ted McCormack
