I have seen the light!

At some point in your life you will peer up into the sky and see the stars. When you do, it is important to note that you’re looking up into a time machine. Even looking at the reflection of the sun off the rippling water is old, time-wise. In our society of immediate gratification, I think we completely lose sight of this limitation.

We flip a switch and the light turns on, we flip a switch and the light turns off. I can remember a specific moment in my life when I giddily tried to move faster than light. I would stand at the switch by the door, flip it off and run to my bed as fast as I could before the incandescent filament dimmed to darkness. I thought I was the fastest kid in the world. That is, until I tried to race Nannette Grace and she whooped my butt, easily.

Light travels extremely fast. On earth, it would almost appear that light is instantaneous but it is not. Just like it took time for us to pack up the car and leave for a weekend up at the lake, it takes time for light to travel from its source to its destination. A light year is the distance that light travels in one year.

Set an alarm on your smart phone so that it goes off in 8 minutes. I’ll wait… From the time that you set that alarm until the time that it goes off, the light from our sun left our sun and reached the earth. The heat you feel from that yellow ball of fire takes about 8 minutes to reach your face. Hopefully you have some sunscreen and sun glasses.

In the winter, our night sky is graced with the appearance of the, ‘Dog Star’, Sirius. It is the brightest star in the sky, shining bright blue. It is twice the size of our sun and is 8.6 light years away. That means that the photons of light it ejected when I saw it 8 years ago, is just now reaching my eyes. So it goes without saying that the first time I looked at the stars, almost 30 years ago, those stars that were 30 light years away are just now reaching this planet. It’s like the past has come to greet me. Each day that passes in my 39th year of life, the photons from the stars that I saw 30 years ago, as a child, are now bouncing off my retinas.

If we could see the stars on the opposite side of our galaxy, we could say that it has taken the entire span of the existence of modern humans for that light to reach us, which I think is somewhere around 200,000 years. However, the thick cluster of stars and gas that surround the center of our galaxy occludes the stars on the other side, so we can’t see them.

Lastly, I would like to bring up the furthest object visible to the naked eye in our sky. The Andromeda Galaxy is the closest galaxy to our own at 2.5 million light years away. The genus, Homo, was just about to start walking on two feet, ready to split off from the previous stage of evolution of ape-like creatures that are our ancestors.

So here we are in this moment, now understanding that the things we see now aren’t what they were a few seconds ago. The action takes place in the distance but seeing the action takes exactly as long as it takes for the light to reach our eyes. It is not instantaneous. This is just one aspect of our universe that inspires me to learn and then comprehend my place in it.


~ by aeroslin on January 27, 2011.

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