The Perfect Speed of Light
A Perfect Balance > We take the instantaneous world around us for granted, to be sure. As we sit or walk or drive or fly, our environment seems to be there with us step by step; there is no apparent lag between the time some nearby event actually occurs and the moment it gets to our eyes.
That is due to the fantastic speed of light. Traveling at over 186,000 miles a second, the light bouncing off your kids or that car or yon bird gets to your eyes so tremendously quickly that we are essentially seeing those events instantaneously.
Imagine, though, a world where light was much slower. Imagine that light travelled only a couple yards per second instead of thousands of miles. It would be a world of mass confusion. You could turn on a light and only gradually would the room come into the view in a wave of illumination. Your spouse could get up to go to the kitchen and you wouldn’t even see him get up until he was already over opening the refrigerator. Imagine the mess driving would be with slow light!
Just about anything involving movement would be such a warp of visual confusion that life as we know it would simply end. Your entire waking life would be a nightmare of delay.
Now this is never going to happen. My immediate point is that the superfast speed of light makes it seem like everything around us is true and precise, and that makes life very comfortable.
But though we are thankful for that great speed, astronomers are glad it doesn’t go faster.
If the speed of light were really instantaneous, astronomy would not have that great opportunity to see the past as it happens. Bear with me here...
Since light does have a speed limit, it does take some time for it to reach us. But it isn’t until we cough up big distances that we even notice.
The moon is far enough away that it takes light over a second to get here. Thus, we see it as it was a second ago. The sun is far enough away that it takes its light over 8 minutes to get here. Therefore, we see the sun as it used to look, over 8 minutes ago.
Go way far away, to the nearest other big galaxy, Andromeda, and we see it as it “was” over 2 million years ago. With the best telescopes, we can see well over 10 billion years ago into the past and every era in between. Studying that past, right up to the present - by watching it actually happen - helps us figure out how the Whole Show proceeded from Act I until now.
The speed of light is fast enough for a wonderful life here, but slow enough to let us watch the history of the entire creation.
Posted by Mark Ritter at 2009.02.23 06:14 PM | Comments (0)
