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 wo nd er fu l c ol or s , 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...