Pondering Light Years

Technology capable of imaging cosmic formations at unattainable distances from Earth, led to pondering light years. Most everyone knows the terminology, understanding at some level the vast, unimaginable scope of our universe. I find myself wondering how many actually comprehend the magnitude of a light year. In the spirit of imagination and wonder – my armchair grasp of light years….

Light reigns as “fastest” in the known universe – 186,000 miles per second to be precise. To put this in perspective, in a single second traveling at the speed of light you would circle the equator 7.5 times. Multiplying the number of seconds in a year by the speed per second, you would have to cover 5.88 trillion miles in a year. Putting close to 6 trillion miles a year in perspective is mind numbing. Try picturing a light minute – it takes about 8 minutes for sunlight to travel 93 million miles to Earth. Visualize 525,600 minutes in a year, ponder 8 of those minutes evaporating in 93 million miles to the Sun.

American astronomer Robert Burnham Jr. published Burnham’s Celestial Handbook in various forms between 1966-1978. Burnham popularized the astronomical unit or AU. One AU = 93 million miles and/or 8 minutes of light speed. Coincidentally the number of AU in a light year and inches in a mile happen to be 63,000. All you have to do now is draw a mile long line in the sand to represent a light year – one inch of that line is the distance to our sun.

Extend that mile long line to slightly over 4 miles, you’ve arrived at Alpha Centauri, the closest star system to our own, 276,000 times the distance from Earth to the Sun. If modern technology attempted the 4 light year road trip to Alpha Centauri – it would take well over 100,000 Earth years.

Ponder 26,000 light years to reach the centre of our Milky Way galaxy, estimated to be over 150,000 light years wide. The Andromeda galaxy is 2 million light years away.

Contemplating light years is heady stuff. The next time you gaze at night’s sky, take a moment to wonder. Ask yourself how  long it took for starlight to cross the cosmos.



3 thoughts on “Pondering Light Years

  1. I would teach that to my 6th grade students using an example of a telephone call from Earth to someone on a planet in the Solar system, then go from there… I would lose them after talking about how far were the closest galaxies, and the theory of multiverses.

  2. My head hurts! When it comes to distances I know my butt gets tired after about 200 miles. And nowadays I’ve gotten quite happy driving 57 mph seeing as that’s the sweet spot on our Motorhome. I’d never be good at explaining the speed of light. Maybe that’s why I don’t spend as much time looking at the stars as I might. Hmmmm…..

  3. Light years are hard to imagine because we use our estimated life expectance as a bench mark (<100 years). If we took the age of the universe as a benchmark( which seems more appropriate), i.e. 13.8 billion revolutions of our earth around our sun, than galaxies and milky ways are ridiculously close. These are different perspectives. In our own perspective we are really important and the universe is outrageously big. As big as God. In the other perspective, the universe is normally sized and we are as insignificant as dust. Take your pick J

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