The key difference is that instead of focusing the light on a strip of photochemical film as in traditional cameras, digital cameras use an image sensor, called a charge coupled device (CCD), to capture the image.

FORBES: Technology briefing

Since the speed of light through a cable is consistent, the difference is entirely in the length of its path.

WSJ: A Dive Into the Digital Deep

Because radiation from the Crab nebula is so energetic, the electrons that created it must have been travelling very close to the speed of light so close that the difference between the two speeds would bump up against Planck-scale graininess, and show up in the spectrum of the radiation.

ECONOMIST: Planck-scale physics

The color of the light is mathematically determined by the energy level difference.

FORBES: LED Light Bulbs Mature At Last

In terms of civic knowledge (questions 1 and 2), the authors found a significant difference in learning outcomes by country, which should probably be seen in the light of the widely different approaches to civic education in the countries.

UNESCO: Article on assesment

All of these questions can be explored in the interactive calculator CNN created to help shed light on the difference in legal protections among the 50 states.

CNN: America is at a crossroads on gay rights