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« Roy Zimmerman on Christmas | Main | Some Pig ... »
How far is a lightyear?
Category: Cosmos
Posted on: December 15, 2007 9:00 PM, by Greg Laden
Find more posts in: 
Physical Science
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TrackBack URL for this entry: http://scienceblogs.com/mt/pings/58199
Comments
It's a great big universe and we're all really puny
We're all tiny little specks about the size of Mickey Rooney
It's big and black and inky
And we're all really dinky
It's a big universe and we're not
Posted by: Mike Haubrich, FCD | December 15, 2007 10:22 PM
Useful tidbits of measurement:
An astronomical unit is almost exactly 499 light-seconds. (Very easy to remember.)
In one nanosecond, light moves very nearly 30 cm, which is almost a foot.
The Earth's circumference is very nearly 40 megameters. (Easier to remember than radius.)
Posted by: 6EQUJ5 | December 16, 2007 5:26 AM
I just would like to clarify some information given in the video may confuse some readers (listeners) of this blog. It says radio waves and electricity move at the speed of light. First of all, no object can move at the speed of light unless it is massless (Special theory of relativity). Radio waves is actually part of light so it of course moves in the speed of light, but it is not another kind. On the other hand, electricity or signal do not move at the speed of light. It is close, but it does not. For more information about the speed of electricity you can find some at the following: http://en.wikipedia.org/wiki/Speed_of_electricity
Posted by: Jo | December 16, 2007 11:13 PM
Jo,
Thank you for the clarification. I had meant to include a note to that effect along with the video,
The electromagnetic energy wave traveling through a vacuum goes at the speed of light, but such as wave traveling through a conductive solid goes WAY slower, not just a little slower.
Posted by: Greg Laden | December 17, 2007 7:01 AM
so please exlain about any outer living planet besides earth
Posted by: kumarvenkatesh.kadam | January 31, 2008 7:40 AM