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Comment by BartBoch | Hacker News Reader

As always, soon we will discover another way, or there will be a different theory that will allow bending the rules.

Not always. Faster than light travel has never been bent.

Well, we are able to research FTL for only a few decades. Give it a few more due to complexity. Few ages ago people thought that the world is flat...

Also, there are theories of FTL: https://en.wikipedia.org/wiki/Faster-than-light

> Few ages ago people thought that the world is flat...

Ah, no they didn't. Scientific consensus has been the earth is round for thousands of years.

As the word 'age' is used in the original comment, a likely synonym is 'millenia', so you are in aggreement with the poster.

They didn't really, that's a common misconception: https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth

And suddenly people think the earth is flat again ... we need to keep science more relatable to the general population and that starts with being realistic.

I'm not arguing with your idea ... just that it should start with a caveat ... "there are no current theories that support FTL but we're hoping ..."

Shadows can move faster than light.

Shadows are an abstract concept (namely, the absence of light), not a physical thing.

I would argue that shadows are a very physical effect.

That's an interesting assertion... Why would shadows be able to move faster than light?

It's perfectly correct and does not contradict physics. Think about it in the opposite direction - say you have a perfect laser, with perfect pointing ability. You pick two planets that are far away from each other but at roughly the same distance from Earth, and make an angle of 10 degrees with it; it will take you a few seconds to "move" the laser 10 degrees and thus move the spot from one planet to the other - in the process making the spot "travel" millions of light years in a few seconds. However, the light itself has not traveled at faster-than-light speeds (it still takes a lot of years for the light from your laser pointer to reach any one of those two planets).

There's two possible interpretations here. The implication of "shadows travel faster than light" is that information about the lack of light is faster. This interpretation is false. In your thought experiment, the information of the lasers moving still only travels at speed of light, even if the actual movement took only a fraction of that time. So the "shadow" on Earth reacts at the speed of light to changes in the source.

However, if the idea is that a laser that is continuously lit can "sweep" a path, such that the laser dot appears to move faster than light could travel that same path... Then of course that's trivially true. The light is traveling the radius of the arc, not the length.

> It's perfectly correct and does not contradict physics.

Sure, this is correct, but I don't see how this describes anything traveling faster than light. The light spot itself is an effect of the light that's traveled to that point (at the speed of light). The spot "moving" is (physically) more of an illusion as the light now travels to an adjacent location.

As far as I understand it doesn't actually move

Say you're standing in front of the sun and you wave your arm. As the light travels away from you, your shadow will get larger and move faster. Eventually the movement of the shadow will exceed the speed of light. In theory it will approach infinity.

The light itself will continue to travel at normal speed but if you waited for the light to bounce back from distant planets you could observe the shadow moving FTL.

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