To carry out a warp trip, you have to arrange space -time so that you never travel faster than light, but still arrive at your destination … faster than light. And in 1994 the Mexican physicist Miguel Alcubierre found out how.
Instead of expanding the space between two points, Alcubierre asked what if they were ordered so that the room was compressed between two points? What if I look at a distant star or a distant galaxy or wherever my goal is, and instead of imagining the space between us, what is ever bigger and larger and larger than in an expanding universe?
Alcubierre was able to construct this type of space -time, in which the distances between you and your goal become shorter by creating a very special type of wave that is moved with the spaceship. So the idea is that you are in your spaceship and you sit in a bladder.
There is a wave before the bladder. You can imagine that a wake that is pressed in front of the bladder. It is not really what happens, but it's a good analogy. And you can imagine that the room in front of the ship will be compressed. It is pressed together.
So if you had a ruler who depends on space and then approaching Alcubierre ship, this ruler will be shorter. It is no longer a meter. It will be three quarters of meters or a tenth meter. It will be literally shorter because the room itself is compressed. This compression of the room in front of the bladder pulls the bladder forward.
And behind the bladder room is stretched out, just like in an expanding universe. They stretch out the room behind them and push them with them.
But surprisingly, it is flat in the bladder. There is no movement at all. If you were in this bladder that we continue and call a warp drive and you sit in the commanding chair of your spaceship, you would not feel anything. You have no acceleration. You don't feel any movement at all.
They don't move according to their local observations. But their goal would get closer to them.
The Alcubierre Warp Drive extends the space behind its bladder and compresses the space in front of its bladder. It reorganizes the geometry of the room between you and your goal, so that you arrive at your goal without moving. And since no movement does not mean a dilution of time, all watches on board the ship with watches agree to inpatient observers outside the bladder.
This means that this wave compression expansion-bladder bladder setup can be made as powerful as you want, which means that the trip can be as short as you want. It could take a year. It could take a microsecond. It doesn't matter. Everyone would agree that they could arrive at their goal (or more precisely, their goal comes to you) faster than light. So if I would send a radio transmission in the “welcome to your goal”, you would exceed this message.
This raises important questions about causality, but that is not the problem of general relativity.
