Hello everybody, here is an article that was forwarded to Astronomy Contact Group by one of the member. I found it very interesting and I wanted to share it with you even though I didn’t write it. Enjoy!
This is particularly true of something we see less and less this time of year: the Sun.
Throughout most of human history, we had no idea the Sun was a star… or that the stars scattered across the night sky were other suns unimaginably far away.
For thousands of years, it was an article of faith that the world was an immovable disk around which the Sun, the planets and the stars all revolved. Everyone believed, indeed knew this.
That changed a few centuries ago. Yet it is only within the last few decades – using everything from ground-based telescopes and spectroscopes to the space-based Solar and Heliospheric Observatory (SOHO) – that we have gained a real understanding of our nearest star.
So let’s take a closer look at the celestial giant on which so much of our lives depends…
The Sun is 93 million miles away. A passenger jet flying 550 miles per hour would take 20 years to get to the Sun. To reach the next nearest star, Alpha Centauri, that same plane would need five million years.
The Sun is by far the largest object in our neighborhood, making up 99.8 percent of the mass of the solar system. Its diameter is 865,000 miles. Were it hollow, 1.3 million earths could fit inside it. Yet, in astronomical terms, the Sun is just an average-sized gas ball – out of some 200 billion – in the Milky Way galaxy.
Things look fairly placid here on Earth, if not downright stationary. But that is an illusion. The Earth spins on its axis at 1,040 miles an hour while chugging around the Sun at 66,600 miles per hour. Meanwhile, the Sun – with its retinue of planets – is screaming around the center of the galaxy at 483,000 miles per hour while the Milky Way itself moves toward the Andromeda Galaxy at a hair-raising 1.3 million miles per hour. (And you wonder why you always feel rushed?)
The Sun is the most alien place in the solar system. Its interior is unimaginable hot – at 27 million degrees Fahrenheit – and converts 400 million tons of hydrogen into helium every second. Indeed, conditions there are so extreme that hydrogen and helium atoms break into their constituent parts – protons and electrons – and re-fuse into heavier elements. That process – called nuclear fusion – is what makes stars shine.
Author and astronomer Bob Berman writes, “The power of the Sun’s continuous nuclear fusion is equal to 91 billion megatons of TNT per second. That’s 91 billion standard one-megaton H-bombs going off in the time it takes to say ‘Holy moly.'”
Fortunately, we’re a safe distance away. In fact, we’re the perfect distance away. Venus is a boiling mess. Mars is a frozen desert. But you and I are here because we inhabit “the Goldilocks zone,” a region where temperatures are moderate and water can exist as a liquid.
We are all tied to the Sun in the most intimate ways. It is the master timekeeper, marking off our days and nights as well as the years. The Sun drives our weather and climate and even affects your moods.
Psychologists are familiar with something called Seasonal Affective Disorder. When the skies turn grey, the weather cools and the days shorten, our bodies slow down, our energy wanes and our outlook darkens. Your biological clock and even your disposition are affected by sunlight (or the lack of it).
In fact, we need this precious resource to live. True, too much sunlight is damaging. But too little is dangerous, too. Sunrays generate Vitamin D, a substance that strengthens your immune system, protects against rickets, and combats osteoporosis, multiple sclerosis, rheumatoid arthritis, hypertension, diabetes and influenza.
Vitamin D is the most powerful anti-cancer agent ever discovered. Researchers say you should enjoy 20 to 30 minutes of sunshine before applying sunblock.
Not just our planet revolves around the Sun, but life itself. Through photosynthesis, plants convert sunlight into usable energy, kicking off the food chain and creating the foundation for the entire web of life.
The Sun is responsible for most of our energy, too. In “Chasing the Sun,” Richard Cohen writes, “The Sun is the great self-renewing resource, the creator of coal, peat, oil, hydroelectricity, and natural gas. It raises moisture into the atmosphere, to return as the downpours that drive turbines; it powers the winds and the waves, and all their effects; it lavishes itself over the entire planet, delivering to the Earth’s surface more energy in just forty-four minutes than we use in a year.”
The Aztecs and Egyptians worshiped the Sun, as did the Persians, Incas and Tamils of southern India. Grand monuments to it still dot the globe, from the pillars of Stonehenge to the Great Pyramid at Giza to the temple ruins of Machu Picchu.
This is not surprising, really. Consider how many ways the Sun resembles the traditional image of a deity: It is a mysterious enigma, ever-present, powerful beyond measure, a giver of light, responsible for life on earth, yet too terrible to gaze at directly.
Sun worship stemmed from a fundamental truth: Without our nearest star, life on earth wouldn’t exist.
Yet knowledge about the Sun was not easily won. We had to wait for the advent of the telescope and the scientific method. Isaac Newton, in fact, spent so much time studying the Sun that he had to shut himself in a darkened room to wait for the full return of his sight. It took three days.
Dutch philosopher Spinoza ground the mirrors for his own telescope – and died at 44, his lungs rotted from year of inhaling glass particles.
Early church authorities tried to strangle the science of astronomy in its cradle, insisting it undermined the Bible’s geocentric view of the universe. Joshua commanded the Sun to stand still, not the Earth, thundered Martin Luther.
When Italian astronomer Giordano Bruno openly theorized that the Sun was a star and the universe might contain other worlds, he was promptly put to the stake. Galileo, the father of observational astrononomy, was forced to recant his heliocentric views and placed under lifelong house arrest. Scientists quickly got the message, privately declaring that it was better to be humble than hanged.
Progress and scientific understanding could not be stopped indefinitely, however. Today we know the Sun influences crop yields, global temperatures and ocean currents. Solar eruptions – caused by intense magnetic activity – affect the position and strength of the Gulf Stream, the frequency of auroras, the clarity of radio transmissions, the longevity of Earth satellites, the thickness of the atmosphere and the condition of the ozone layer.
The atoms that make up your body were forged in the heart of ancient suns. The iodine in your thyroid gland was fashioned from supernova material. The iron in your blood came from the cores of previous star generations. As Carl Sagan famously declared, we are star stuff contemplating star stuff.
The Sun is the lamp of the world, an awe-inspiring, life-giving ball of fire, a constant source of comfort and wonder. Throughout history, it has dominated art, language, religion and science. It is the great muse of artists, responsible for glorious sunsets, dazzling rainbows and the ethereal Northern Lights.
Yet there is much about the Sun we simply don’t know. Scientists are still trying to understand what causes sunspots and solar winds, how its magnetic particles affect the Earth’s climate and how the Sun’s rays can be cost-effectively captured.
New spacecraft are even being designed to harness its power. Engineers are betting that some day – many years hence – it might be just the right fuel to carry us beyond our dying star’s grasp and out of the solar system… in search of another Sun.
By Alexander Green published on Friday, December 2, 2011 in a Magazine