I am not a physicist, so apologies if this is something that has been discussed before and is well understood. I, sort of, understand why it has been theorised that light (or mass) has a maximum speed that can't be exceeded. Also that experiments have shown it to be 299,792, 458 m/s in a vacuum. But I haven't seen whether there is a good theoretical reason that the maximum speed should be at that level. Why, for example, shouldn't the speed of light be 250,000,000 m/s or 350,000,000 m/s? Put another way, what is special about that speed?