In computing, the speed of light fixes the ultimate minimum communication delay. When communicating with distant space probes, it can take minutes to hours for signals to travel. Any starlight viewed on Earth is from the distant past, allowing humans to study the history of the universe by viewing distant objects. For many practical purposes, light and other electromagnetic waves will appear to propagate instantaneously, but for long distances and very sensitive measurements, their finite speed has noticeable effects.
All forms of electromagnetic radiation, including visible light, travel at the speed of light.
