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Pluto flyby reminds us just how small we are.

Byline: Greg Jewell For The Register-Guard

As the New Horizons spacecraft passes Pluto's orbit, we're reminded that in the past few hundred years humanity has evolved from considering itself the center of the universe to realizing we are an infinitesimal speck among billions of stars in one of billions of galaxies. How can we relate the vastness of space to a more everyday scale?

Let's start with the Earth, which might seem like a big place. Suppose it were the size of a blue racquetball. On that scale the Moon would be a white marble, roughly 5 feet away.

To expand our cosmic view to our solar system, we need a new scale. Let's reduce our sun to the size of a basketball. On this new scale, the Earth would be slightly smaller than an air-gun BB more than 80 feet from the sun.

Mercury, the planet closest to the sun, would be about 30 feet away from it. Jupiter is 430 feet down the street. Pluto averages 3,300 feet from the sun, or more than six tenths of a mile.

The star nearest to our own is Alpha-Centauri, 4.3 light years away. A light year is the distance light travels in a year moving at 186,000 miles per second - nearly 6 trillion miles. Light from the sun takes 8 minutes to get to Earth.

On our sun-is-a-basketball scale, a light-year is approximately 1,000 miles, which puts Alpha-Centauri 4,300 miles away. If we put our basketball-sun in Eugene, we would travel to New York City and another 1,400 miles over the Atlantic Ocean before finding the next basketball, with nothing much in between.

To imagine going even farther, let's make our entire solar system, the volume of space within the orbit of Pluto, the size of a BB. The Earth would be only about 15 times larger than an iron atom, and you could barely see the Sun glowing at the center.

The Alpha-Centauri star system (which is actually three separate stars) would be another speck of light about 40 feet away.

Alpha-Centauri is only the closest star. The bright star Sirius is twice as distant. Vega, the "star" of the movie "Contact" (based on Carl Sagan's book of the same name) is 26.5 light years distant, putting it 240 feet away from our BB-sized solar system. Most of the few thousand stars we can see in the night sky are less than 1,000 light years away - which would be more than 1.5 miles on this scale. Imagine walking through these thousands of specks of light spaced about 30 to 100 feet apart.

On a clear and moonless night, however, you can see the blurry backbone-of-the-sky, as some call it, which is part of the billions of stars in our Milky Way galaxy. We live on an outer spiral arm of this disc-like galaxy, a little more than halfway from the center. The 27,000 light years to the galactic center on our BB-sized solar system scale is more than 40 miles. Imagine driving from Eugene to Albany through a billion specks of light that get closer and closer together and bulge several miles high as you approach the galactic center.

Our galaxy is a huge disc about 100,000 light years in diameter. On the scale we're using, our galaxy, filled with billions of pinpricks of light, would stretch from Portland to Roseburg, and from beyond the North Sister more than 30 miles out into the Pacific Ocean. Remember, we're living on an atom-sized Earth in a BB-sized solar system.

Feeling small yet? There's more.

Only about 100 years ago, we thought our Milky Way was the entire universe. We assumed other galaxies were just clouds of dust in our own galaxy. But these dust clouds are actually other galaxies millions of light years away.

Let's take one more scaling step and shrink the entire Milky Way galaxy to the size of a dinner plate, glowing with perhaps 200 billion stars so small they can't be individually distinguished. We've reduced our galaxy, 100,000 light years in diameter, first to 170 miles, and now to the size of a plate you could hold in your hand.

The nearest large galaxy is Andromeda, about 2.5 million light years away. That's a mere 21 feet on this scale. We are part of the Virgo Supercluster, made up of thousands of galaxies extending about 110 million light-years - or roughly 1,000 feet in our galaxy-as-a-dinner-plate scale. Imagine Autzen Stadium filled with thousands of galaxies, many smaller but some larger than our plate-sized Milky Way.

But the clincher is that this represents less than 1 millionth of the estimated 100 billion galaxies extending 20 miles in all directions.

The next time you're outside on a clear night, don't forget to look up.

Greg Jewell of Veneta is a retired electrical engineer.
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Title Annotation:Guest Viewpoint
Publication:The Register-Guard (Eugene, OR)
Date:Jul 15, 2015
Words:818
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