# Speed of light

Light is such a fascinating thing! When it comes to different areas of physics in science, our kids learn about mechanics, electricity, magnetism, heat (thermodynamics), and so on. Personally, I find the topic of LIGHT the most fascinating of all of these!

I'm not sure why that is. Is it because of all the wonderful colors, or because how the wavelengths and frequencies tie in with music, or because of the beautiful sine waves I've studied in math...? I'm left wondering.

Anyhow, I know what you have read... that light always travels with the same speed — THE speed of light — but that's actually not so. Light has a different speed traveling through water, or traveling through glass, or air, or other things. What scientists mean is that the speed of light is this particular number (constant) when light travels through the big open space.

Even Einstein himself... he was toying with pure ideas (they call it theoretical physics), and I'm sure the thought crossed his mind if light could travel faster (or slower) than the "current" speed of light.

Of course, little kids don't even realize light has a speed. I figure that is because light is SO fast, it just seems to "be there"—they don't notice it traveling.

You can explain to them that the LIGHT from our Sun actually takes 8 minutes to reach the Earth, and the light from the stars even longer. The starlight you see twinkling and coming into your eyes tonight may have started traveling thousands of years ago! Or millions of years ago—it depends on the particular star you gaze at (different stars are at different distances from us). And it's only NOW reaching your eyes. Kind of makes you realize how vast our universe is!

You would think that when something is so fast, it must be difficult to measure its speed. But our friends from Supercharged science show us how to do just that with this EASY experiment: measure the speed of light using a chocolate bar!

Actually, you can use other things too. We used crackers covered with cheese—and yes, it did work!

They are doing a promotion right now (August is always full of promotions and sales for educational products, as I'm sure you have noticed). But, promotion or not, the experiment itself is FREE and good!

Have fun!

P.S. Don't forget, I am still running a sale on all Math Mammoth CDs and downloads at Kagi store. 25% off!