# How far is a lightyear?

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## 5 thoughts on “How far is a lightyear?”

1. It’s a great big universe and we’re all really punyWe’re all tiny little specks about the size of Mickey RooneyIt’s big and black and inkyAnd we’re all really dinkyIt’s a big universe and we’re not

2. 6EQUJ5 says:

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.)

3. Jo says:

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

4. 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.