In the past year of blogging for GLAMsci, most questions and feedback came from the speed of light series. I thought some housekeeping was in order to post an answer to the most frequently asked question – why isn’t the speed of light infinite?
To be fair, in my posts I discussed the finding of the speed of light and how it is used as a measuring tool for distance and temperature etc. The speed of light is actually something much deeper.
Does the speed of light actually have anything to do with light? Why does the universe arrange itself to keep the speed of light constant? All 186,282 miles per second in a vacuum for all observers. The universe doesn’t actually care about light, nor does it arrange itself to slow it down or speed it up.
The truth is, the statement is false! Or at least back to front. The speed of light is actually the speed of CAUSALITY. I wrote about causality in my relativity series. To recap, causality in the way of the space time interval is the only thing all observers can agree on.
Not everyone can agree on time, space or sequence of events but everyone agrees on causality. Causality is what is real. What you see right now may not be reality for another observer depending on their reference frame or velocity.
Truth be told, the universe couldn’t care less about the speed of light. It certainly doesn’t arrange itself to keep the speed of light constant in a vacuum. The speed of causality is the maximum speed in which two points in the universe can talk to each other. The sun can’t send its rays or visibility to us here on Earth faster than the speed of causality. That speed is 8 minutes so in reality we see the sun as it looked 8 minutes ago.
It just so happens that the speed of light and the speed of causality happen to be the same but it is the speed of causality FIRST.
So light, electromagnetic waves and gluons all have no mass. A particle’s interaction with the Higgs Field determines its mass and velocity. The photon (light particle or wave) doesn’t interact with the Higgs field so it has no mass.
Without mass there is no restriction on their velocity which means they can only travel at one speed; as fast as it is possible to go.
Electrons protons and neutrons all have mass, therefore can’t move at the speed of light. Anything without mass will nearly always do so.
So why is the speed of light finite? If the speed of light was infinite, all points in the universe would be able to communicate with each other instantaneously. We wouldn’t be able to tell which stars are further away or older etc. Our universe would be one instantaneous here and now. No past, no present and no future. No cause or effect as causality actually means.
Using the famous E=MC2 equation, if the speed of light is infinite it would require an infinite amount of energy to accumulate an infinate amount of mass to keep the speed of light as being infinite.
So always remember that the constant is the speed of causality and the speed of light but the speed of causality first.