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In the beginning, it was all magic.
To our earliest ancestors, the night sky was as overwhelming as it was incomprehensible. It was staggering. It was mysterious. It was scary and exciting at the same time. It was profoundly moving. It was magic.
Humans, however, are nothing if not curious, constantly striving to explain the unexplainable, to peek behind the curtain, to crawl down the rabbit hole, to create order out of chaos. And in the absence of knowledge, they inevitably turn to belief systems, to religions. Early Humans filled the sky with gods and goddesses. They invented astrology. They imagined heavenly bodies having a direct influence on their day to day activities. Why else would they be up there? What could possibly be more important than the comings and goings of Human Beings? They created complicated charts and tables that attempted to predict how celestial objects ruled their lives, fanciful musings that explained everything, and nothing. It was still all conjecture, theory, belief. It was still all magic.
Eventually the science of astronomy was developed, and its mandate was nothing less than the scientific exploration of the entire Cosmos. The mother of all adventures. An empirical journey through the looking glass, to infinity and back. A trek among the stars that has taught us much about the Universe around us. But each new scientific discovery just seems to pose more questions, and as science solves one cosmic mystery, it seems two more suddenly appear to take its place. We have developed technology to leave our planetary home and journey as far as the Moon, and send spacecraft throughout the solar system and beyond. We can now explain many things about the Universe, and every day we learn more. But as much as science can explain, there is much more that it can't. There are forces at work in the Universe that are still completely beyond our comprehension. It has been recently concluded that all the matter we see around us, all the planets, stars and galaxies, all the interstellar dust and gas, every single molecule and atom in the entire Universe, is only a small fraction of what's really out there. The vast empty spaces between stars and galaxies are not empty at all, but filled with an invisible substance called dark matter. We cannot see it, but we can measure its effect on the normal matter around it. Similarly, there is an undetectable force in the Cosmos that makes matter behave in ways it shouldn't. This force is called dark energy. Together with dark matter, it makes up 97% of the substance of the Universe. And we have absolutely no idea what it is or how it works.
The magic just won't go away.
Two thousand years after they were written, the words of the poetess Avvaiyar still ring true:
As Einstein was so fond of saying: it's all relative. In other words: reality is all a matter of personal perception. It's not what you know, but what you perceive that forms your own personal version of reality. For instance, we all know that when we watch the Sun set into the horizon, the Sun isn't really moving. It's the piece of Earth we are standing on that is moving, slowly rotating away from the Sun, and carrying us with it, stuck like so many microscopic little fleas on its back. But even though we know that, we still can't help but perceive ourselves as standing still, and the Sun moving across the sky. A grand and glorious illusion indeed, but the truly perceptive Man has an even grander and more glorious experience. He watches the horizon come up to meet the Sun, feels the mighty Earth rumble beneath his feet as it rotates, turning away from the warmth and light of the Sun, to face the cold darkness of space.
Similarly, most of us see the crescent Moon as a glowing two dimensional vision hanging in the sky, and we are so amazed and moved by its beauty we write poems and songs about it! But once again, the perceptive Man is even more amazed and moved. He sees a massive planet, suspended in the blackness of space, held fast in Earth's gravitational embrace, the Sun like a giant spotlight, hidden in the wings below the horizon, lighting up one side of the Moon like the profile of a lone actor on a dark and desolate stage.
To truly start to understand the Cosmos that envelopes us, we must constantly endeavor to transcend the stubborn illusions of our limited consciousness, and try to wrap our brains around the true size and grandeur of the Universe we live in, each small step on the path to perception rewarded by a wonderful rush of endorphines - like sugar on our tongue - a taste of the infinite.
Some realities, sadly, are beyond our perception, no matter how hard we try. The capacities of our "frail and feeble minds", as Einstein put it, are severely limited. Nowhere is this perceptual inadequacy more prevalent than in our measurement of distances in space/time, and the unit of measurement: the light year. Since light travels at a constant, unwavering speed of 186,000 miles per second (670 million miles per hour) everywhere in the Universe, we can use it to measure both space and time.. A photon/wave of light travels a million miles in the time it takes to count to five, measuring both distance through space (a million miles), and distance through time (five seconds).
To see how close we can come to actually perceiving the reality of a light year, let's start with a trip around the world, about 25,000 miles. Most of us are able to form at least a rough mental image of a straight line stretching out into space 25,000 miles. But how about one million miles? That would be 40 times around the world. A commercial jet that never landed would take more than two months to travel that far. Now stretch that distance - a million miles - in a straight line out into space. Can you really conjure up a mental image of how far away the end of that line would be? If you can, you're doing extremely well. Most of us cannot truly perceive just how far away a million miles really is, no matter how hard we try. Our brains just can't do it.
But we've only just begun! A million miles is nothing in space! Light can travel that distance in a mere five seconds. How can we possibly hope to imagine the distance of just one light minute, or one light hour, let alone an entire light year? If a light year were the length of a football field, we would be smaller than the smallest microscopic bacteria, and the Sun would be a twentieth of an inch away - about one millimeter. We have no more possibility of imagining the distance of a light year, than microscopic bacteria have of imagining the length of a football field.
If we crunch the numbers, we can calculate the distance of a light year as 5,865,700,000,000 miles, but numbers that large are meaningless. They are beyond our comprehension. And that's only one light year! The closest star to our Sun, Proxima Centauri, is 4.3 light years away, and most of the stars in our sky are very much farther away than that. Our galaxy stretches an amazing 100,000 light years across. And once we leave our galaxy, the next closest galaxy, the Andromeda Galaxy, is an unbelievable 2.2 million light years away! We can say the words, we can write them down, we can do the math, but we cannot perceive what they describe. We are like two dimensional beings living in a three dimensional world. We know that third dimension is there, but it's impossible for us to see it, or to even imagine it.
When it comes to the number of stars in our Universe, Carl Sagan's "Billions and billions..." is just the tip of the iceberg. There are more stars above our heads than all the grains of sand on all the beaches in all the world. And then some. In 2004 the Hubble Space Telescope focused on one very tiny, very empty, very black spot in the sky in the constellation Fornax, where there was no hint of anything. It held that focus for one million seconds, a time exposure that lasted 11.6 days, to capture even the faintest trace of light, to see what - if anything - might be out there. The results of that experiment gave us a whole new appreciation of the incomprehensible scale of the Universe we live in. The telescope captured photons of light that had been traveling through space for 13 billion years. In other words, it captured the images of galaxies 13 billion light years away! The resultant photo was called the Hubble Ultra Deep Field, and it remains one of the most important and iconic photographs ever taken.
There are only four individual stars in the above Hubble Ultra Deep Field photo. Only four residents of our Milky Way Galaxy. Everything else, every blur, every smudge, every pinprick of light - too many to count - is a galaxy outside our own. Galaxies behind galaxies behind galaxies. Untold numbers of galaxies stretching 13 billion light years back through space and time. Each galaxy an island universe, containing hundreds of billions of stars like our Sun. And that is just one microscopic fraction of the entire sky! In one fell swoop, the Hubble Space Telescope has graphically illustrated just how small we really are, and how impossible it is to even begin to perceive the true scale of the Cosmos. But that doesn't mean we shouldn't try, because if we truly open our minds, the fates will occasionally lift the veil, and favor us with a quick glimpse of what's behind the magic, and sometimes a glimpse is all it takes to alter our perception, and change our life.
As Einstein proved, space and time are inseparable. They are two interwoven components of the same thing. When we look at a star 10 light years away, we are transported ten years into the past, because it took ten years for the light from that star to reach us. We are being visited by a ghost who lived ten years ago. When we look at the spectacular Andromeda galaxy, we are being visited by a very old ghost indeed. A ghost that lived over 2 million years ago! We have no idea what the status of the Andromeda Galaxy is right now, if it still exists at all. We're just too far away.
Einstein also proved that the faster you move through space, the slower you move through time, and at the speed of light - 186,000 miles a second - time would theoretically come to a complete stop. Einstein discovered that time was not a linear constant as it appeared on the surface, but that time was in fact a non-linear variable, that was subject to manipulation, and change. A concept as difficult to perceive as a light year, but just as true, and just as real.
Someday Man will learn to move through time, just as he learned to move over the oceans, and up into the air, and out into space.
But first things first. Let's get our bearings, and find our way around, starting with our own neighborhood: a group of planets and other things held captive by the gravity of a star we call the Sun - our solar system.
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