The speed of light is known as 300,000 km/s and we leave it at that. But this speed is only the speed of light through a vacuum and light doesn't always travel in a vacuum. The slowest recorded speed of light is actually 17 m/s, a speed easily attainable by a car. So what happens then if particles can travel faster than light? Well in many nuclear reactors, this is what happens. Particles travel at a speed greater than the speed of light in that specific atmosphere. When this happens an emission of blue light emerges. This is called Cherenkov Radiation and it can be compared to a sonic boom, which happens when an object is travelling faster than the speed of sound, but with light. It is interesting the concrete ideas we have about physics and specifically light, but all of these concrete "facts" can be manipulated and produce unforeseen outcomes.