The Speed of Light is NOT About Light | Space Time | PBS Digital Studios

[Steve Williams]

 

[GaryProtein]

I saw this one right after I saw one you posted several days ago.

It is well worth watching. As Mr. Spock would have said, "fascinating."

 

[Folsom]

Here's another puzzle... What happens if something did exceed the speed of light? As the video points out it's a somewhat arbitrary law of physics but there's an interesting consequence to consider if it were to be broken.

 

[amirm]

Here's another puzzle... What happens if something did exceed the speed of light? As the video points out it's a somewhat arbitrary law of physics but there's an interesting consequence to consider if it were to be broken.

From what point of view? Time dilation? Does that "thing" have mass?

At high level, our laws of physics work on basis of fixed speed of light (really massless particles). In that sense, it makes no sense to ask what happens when that is not the case! It is like asking to solve an equation by first throwing out the equation and still ask for an answer for the variables!

 

[Folsom]

Something with mass? Yes. Time doesn't matter. It arrives before light no matter if you're with it or watching. It's not important if it takes 1 second or billions of years. This is independent of light.

 

[amirm]

I am sorry Folsom. I don't know if you are asking a trick question or simple application of Special Relativity. If it is the latter, the answer is simple. An object with mass requires infinite energy to go at speed of light. Likewise, its mass becomes infinity. This is due to Lorentz Factor (?) which is equiv. to = 1/sqrt(1 - v^2/c ^2). This is why only massless particles can travel at speed of light. And of course light just means photons which is just an example of a massless particle.

From the point of an observer, the object as it accelerates toward speed of light, it will look like it is traveling slower and slower. That is what happens as an object is pulled into a black hole.

I can keep going but is this what you are asking about?

 

[amirm]

BTW, speed of massless particle is not an arbitrary number. It is one of 20 or so constants in our universe that make it be what it is. Why that number and nothing else is what occupies the time and brains of many theoretical physicists. Are we the only example of all of these parameters coming together to give birth to the universe as we know it? What is the universal formula/law that allows computation of these constants? Are there other universes with different constants that also work?

So much of quantum mechanics for example relies on plank's constant which is 6.62607004 × 10-34 m2 kg / s. That is 10 to the power of -34. How could such a tiny number be so important? And why that specific value?

 

[Folsom]

The question isn't how something with mass would travel faster than light, it's what if it did.

 

[amirm]

It would no longer be part of our observable universe since it breaks causality. Time will become imaginary, etc. When something can't exist, we don't ask if it did, what would then happen.

 

[Folsom]

Ah, would it cease to exist or would casualty change. Self destruct existence? Restructure? Who knows. Maybe it would be benign so long as it happened within the limits of existence, and now at the edge of it...

 

[amirm]

"Cease" would imply causality (being to not being) and that does not exist due to discontinuity at v=c.

Other universes with different constants and laws may allow it to exist but they cannot co-exist with ours. Any intersection would annihilate both.

 

[Folsom]

That's what we assume.

But we have blackholes, that appear to defy everything. And we don't know the full power of dark matter, and it's potential abilities to act upon the situation.

 

[Whatmore]

Here's another puzzle... What happens if something did exceed the speed of light? As the video points out it's a somewhat arbitrary law of physics but there's an interesting consequence to consider if it were to be broken.

This is where we need to be clear about what we say. C is the speed of light in a vacuum. No particle with mass can travel *at* c.
But...
Particles can travel faster than the speed of light when the speed of light is less than c. This is what happens with cerenkov radiation.

Also, the theory holds that nothing with mass can travel at c, but it does not say it can't travel faster - tachyons