Answers With Joe

Why Is The Speed Of Light The Speed Of Light?

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Today I answer another question from my 50-question lightning round video, this one on the speed of light.

Transcript:

So when we talk about the speed of light, the first thing to remember is that light is just a sliver of the entire electromagnetic spectrum, ranging from gamma rays to radio waves.

So we’re really talking about the speed of electromagnetism.

James Clerk Maxwell was the genius who first described the properties of electromagnetism into physics equations.

From these equations, we can calculate the speed of light. 299,792 kilometers per second.

Einstein was able to prove through his theory of special relativity that the closer you get to the speed of light, the more time slows down for a person in that relative frame. And if you were to go the speed of light, time would stop altogether.

So if you were able to travel faster than light through spacetime, time itself would actually flip. Time would go backwards. And that would break causality.

Effect would precede cause, which is impossible. The speed of light is the speed of causality.

The other prediction that supports a speed limit is the idea that inertia increases as velocity approaches the speed of light. That means mass increases.

So mass is a speed impediment. Nothing that has mass can go the speed of light.

But if you are massless, you can only go the speed of light, because you have no speed impediments. And photons are massless particles.

Particles that must travel at the speed of light and because they are traveling at the speed of light, time stands still from its point of view.

So really, that video I talked about earlier is all wrong, from the perspective of the photon, that journey would have occurred instantly.

So when you look at a star at night, that massless photon might have traveled a million light-years to reach you, but its experience was instantaneous.

Now there is another theory that’s a little controversial but starting to gain some ground.

It says that the speed of light is actually caused by quantum vacuum fluctuations.

See, quantum field theory claims that empty space is actually not empty at all but filled with quantum fluctuations and virtual particles popping in and out of existence.

And two different teams of researchers have calculated c using electromagnetic properties of the quantum vacuum, so it could be that the quantum foam of virtual particles and fluctuations may be slowing the speed of light.

But what if the speed of light wasn’t the speed of light?

What if Galileo was right and the speed is infinite?

Then nothing would exist. Because matter is made of energy, it would take infinite energy to create any mass. Time and space wouldn’t exist because all things communicate with each other instantaneously. Cause and effect wouldn’t exist.

But if the speed of light were slower, that might be even cooler. Because then we could see all the way back to the big bang.

The speed of light, of course, is just one of many constants in the universe, like gravity, the specific charges and masses of the fundamental particles, quantum effects, and the list goes on.

A whole handful of very specific constants that if they were just a little bit different, we would never exist.

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