The Parsec

According to the Public Broadcasting System educational television program, NOVA, “A parsec is equivalent to 3.26 light years.” According to the National Aeronautics and Space Administration (NASA) website, Ask an Astronaut, a light year is, “The distance light travels in 1 year,” which is 5,878,786,410,000 miles per year. With that information, we can find out just how far away a parsec is. If we take the miles per year and multiply it by 3.26 years, we discover that 1 parsec equals 19,164,843,696,600 miles.

So, where then, does the term, parsec, come from? Parsec is a combination of 2 words, parallax (par) and second (sec). Parallax means something looks like it changed its location because you changed yours. For example, if you stand on your porch and look across the street, you will see a house on your left and a house on your right. If you go across the street and look at the same houses from your neighbor's backyard, they will be on the opposite sides. Did the houses move? Of course not. You changed your location. Since you are in a different place, facing a different direction, they appear to be in different places. Likewise, two different people, in two different parts of the world, might see the exact same event in the sky or outer space; yet, it might appear entirely different due to their locations.

In this instance, when we use the term, second, we are not referring to a measure of time. It is a part of a degree. Not the kind of degrees we use to tell the temperature, either. These degrees are part of an arc or a circle, as in a circle has 360 degrees. When you look at a globe or map, the lines on it running from top-to-bottom are degrees of longitude. The ones running side-to-side are degrees of latitude. Each of those degrees is made up of smaller units. Just like the hour is the largest unit on a clock, which get broken down into smaller pieces, too. What makes it easy to remember is they have the same names and values. One degree is made up of 60 minutes. Each minute is made up of 60 seconds.


Stephanie Louise B.

"A Stephanie of All Subjects"

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