Is there a limit to how fast we can go, how much space we can cover over a unit of time? Take a look at the speed of thought, speed of light, and sound. If you accept that time is an arrow pointing in one direction and that everything that happens takes some amount of time along that pointer to happen, then it is an interesting exercise to think about different speeds. Some physicists propose that time is not a real thing after all, not in the way that we think about it. Julian Barbour explores this in his book The End of Time: The Next Revolution in Physics. Check it out from you local library if you are interested. But for now assume that time is what you think it is. Consider some of the ways that we measure things that move or happen with time.
The Speed of Thought
Early in my college career I remember the first time I heard somebody say: “The ultimate thing is to learn to travel at the speed of thought.” It was in the context of talking about spaceflight at a party. The person speaking was the non-technical wife of another engineering student. I learned in high school electronics shop that electrons in a wire travel relatively slowly, on the order of a few cm/second. However, the electric field travels at light speed. If the brain were copper wire, then the speed of thought, measured as the speed of electrons, would be very slow indeed.
Researchers at John Hopkins University did some studies about how fast thoughts form, and came up with 550-750 milliseconds, which is .550 -.750 seconds. But that is the speed that comprehension happens. The nerve impulses themselves that form the thoughts can travel as slow as 2 miles an hour, up to about 200 MPH. In school I was told 650 miles per hour, but here teachers are wrong too. So the speed of thought is a few hundred miles-per-hour (MPH) at best. This would very slow ride to another planet.
The Speed of Light
Albert Einstein developed his theories of relativity by doing thought experiments. His most famous was about light. From that thinking and some mathematics he postulated that the speed of light had to be a constant in order for his theories to work. Light must travel at exactly 670,616,629 MPH in a vacuum. It cannot go faster and it cannot go slower. In water, glass or air it will have a different constant speed, but always a constant that cannot be changed. And scientists think that nothing can go faster than light.