The speed of light is contant and invariant IN SPACE. In time the speed of light is zero

That means that for light its speed in:

space is C in time is 0 in spacetime is C

Now lets see about the speed of a person on Earth riding a bike...

The guy on the bike is moving very slow (compared to light) in space. Lets say that he is moving at 2.7 m/s in space. But the person is also moving at 299.792.453,3 m/s in time!

If we add them together we see that 299.792.453,3 + 2,7 ms = 299.792.458 = the speed of light!

:O

Both light and me on the bike, we are both moving in spacetime AT the speed of light!

So first of all, every object in the Universe is moving in spacetime AT the speed of light. So the speed of light is not unique to light, its the same for everything. Light just happens to have all its speed in space and zero in time... Most objects have most of their C speed in time and a tiny fraction of it in space...

So since both the guy on the bike and light are traveling at the speed of light, why do you only ask about light and not about the bike guy!?

They are both traveling at the same speed!

The reason why the speed of light is so "spooky". Is because when we measure the speed of something, we only care about that something's speed in space... We completely forget that the same object has a speed in time too!

So the speed of light is not constant just for light. Its constant IN GENERAL for everything! But no necessarily in space. Most objects move in spacetime. Light moves exlusively in space and not in time.

Also... "Why is the speed of light in space invariant unlike any other speed" (I hear you asking).

Well, every other speed of every other object is invariant... But not in space... But in spacetime!

My speed in spacetime riding the bike is equal to the speed of C and that's also invariant... Just like the speed of light is. But when you measure the speed of a bike coming towards you you don't find it invariant because you forgot to measure its time speed. If you did, and you did combine those two speed, then you would have found that the bike's speed in spacetime is always equal to C, no matter who's observing is always invariant!

So again, no paradox!

Light is just photons that are massless, so their speed is 100% allocated in space... More massive objects like bikes, allocate their speed mostly in time, and their speed in space is very slow (because it now takes energy to move all that mass! But for light it doesn't!).

Also, also, you are asking "why nothing can't move faster than light?"

Well... Faster than light where?

In space? In time? Or in spacetime?

spoiler alert, if you travel faster than light in any of the 3, you will break causality, so you can't do that!

But you can infact kind of travel "faster than light":

The way that you do that is by simply traveling close to the speed of light in space... When you do that your speed in time will start to decrease, making you experience less and less time.

If you travel sufficiently close to the speed of light in space, you will be able to reach insanely far away objects withought ever experiencing the in between journey... For you those trips will have only lasted for a couple of days, when in reality, for the people there, entire centuries might have passed!

We call that proper velocity.