[DexesTTP]

To simplify, the same way that a surfer on the sea can use the movement of the sea itself (waves) to surf!

An Alcubierre drive (they're theoretical) would basically constantly compress the time curve of spacetime in front of the craft, allowing the craft to "ride" this compression as it moves forward, which means that the local speed of light of the craft is faster than the speed of light of an external observer. Note that the main issue we have is to find something that can compress space, and then to have it have enough energy for it not to be trivial (because 110% of the speed of light, while technically FTL speed, is still very slow for interstellar travel). And of course, while the existence of something that does this spacetime curve compression fits the math we have, we've yet to find a material or technique that actually does so.

[amelius]

Sorry, I don't get it.

Imagine you are on a rubber ruler. You can move at most 1 mark per second on the ruler. This is true regardless of how much the ruler is stretched or compressed.

So to move from mark 1 to mark 100 will always take the same time at top speed, regardless of any stretching/compression.

[cglan]

Don’t take my word at all, but I think in your analogy you can’t imagine it as you’re only allowed to go 1 ruler tick a second, but imagine you can only move 1mm per second. If you compress the rubber ruler you traverse more ruler per second than before while still going the Same speed

[dotnet00]

The idea is similar to how we detect gravitational waves in interferometers, when space gets compressed, the distance the photon has to travel shrinks slightly.

To take your ruler example, if you compress it by 1mm, you can traverse its entire length traveling 1mm less than before, thus, from the reference frame of someone who can't see that you've compressed the ruler, you've traveled slightly faster.