This isn't true. Nuclear pulse drives built with currently available technology could achieve .05C [1], meaning a 4 light year trip would take ~80 years.
[1]: http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi...
Edit: I'm also having a slight chuckle at the estimated costs presented. Somehow, I'd think that just getting 40,000,000 t of spaceship into orbit would cost a bit more than 1 year of US GNP.
You could literally lift a city-sized space ship to orbit on the cheap with this technology. The problem is the nuclear fall-out for those left on the ground.
Consider a warp drive that transports you from, say, earth's orbit to pluto's orbit. Now, you fall back towards earth's orbit. This means that the warp drive, in order to not violate conservation of energy, must require at least as much energy as the potential energy difference between the two positions.
In fact it is possible to build a perpetuum mobile by just filling some region of space with dark energy. This region of space will then expand at constant energy density, therefore creating energy.
Maybe that's really what killed the dinosaurs.
Is your family at home going to be older when you come back from one of those trips?
Even if that was not true, how will the warp-drive propagate the warp-bubble field itself faster than C to grab onto space-time in a timely manner?
It would seem to me this would cause the space-ship to feel that it's traveling faster than C, but to an outside observer it would only be traveling at C or less.
Warp drive will allow humans to pollenize, not colonize, other planets.
I don't know enough special relativity to do the calculations, but if this device is constructible I would expect to have huge modifications in the time coordinate. Just in case, say goodbye to everyone before leaving.
Basically, the ship is able to traverse distances faster than light can, but it isn't actually moving faster than light.
Time dilation occurs at speeds far less than the speed of light. For instance GPS satellites and jet planes experience measurable time dilation.
I am very curious about the time effects of such a drive. Does the ability to warp space using such a device necessarily include the ability to warp time? Is it possible, within a frame of reference, to locally reverse the arrow of time and thereby reverse entropy within that pocket?
>A beam of light inside the warp bubble will still travel faster than the ship, for instance.
But that beam of light seen from outside the bubble will appear to travel faster than the speed of light.
For instance, assuming the 'string' was made of a tough alloy, would it snap and the coin remain where it was at that time, would the ship be dragged back to where the coin is, or can the question not yet be answered by science?
I ask because, presumably, if the coin can exit and be fine, this could be the basis for some kind of inter galaxy bus, no need to slow down the bus, merely drive your spaceship off the bus and exit the bubble when at your destination.
Sure, but I think (?) the original question was asking about time dilation in the massive sense: i.e., you go on a round trip to some distant point in space and return, and it's only been a few days for you, but a few hundred or thousand years have passed on Earth. That sort of time dilation.
That sort won't occur with an Alcubierre ship. It's my understanding that the ship isn't actually moving at all inside the bubble -- or, if it is, it's moving extremely slowly.
One of the problems with this approach that has been explored in other papers is that even if you have a warp drive and even if you have actually gotten a ship into it and even if you've managed to point it in the direction you want to go, the collision of the interstellar medium with your warp field tears it apart quite violently and the warp field "collapses". And unlike when they "collapse" on Star Trek and the only manifestation is a polite electronic "whirring" noise, being in a collapsing real warp field is a death sentence, with tidal forces on par with black hole gravitational fields.
Bear in mind, this article only addresses one of the many fundamental challenges to the Alcubierre drive: the energy requirements. Typically, the energy requirement has been considered the primary challenge to the feasibility of the device. But it's not the only one. Science hasn't completely worked out what would happen inside the bubble, or what happens to particles of matter interacting with the bubble at its leading edge. I've heard at least one speculation that the bubble would fill up with Hawking radiation and pretty much roast everyone alive inside it, like a big, interstellar dutch oven.
Another issue is the stability of the bubble itself. Again, the article doesn't really address this issue. But it's a pretty big one.
Here's the summary from NASA:
"Here are four examples [large graphic][1] of what it would take to send a canister about the size of a Shuttle payload (or a school bus) past our nearest neighboring star...and allowing 900 years for it to make this journey.
Well....If you use chemical engines like those that are on the Shuttle, well..., sorry, there isn’t enough mass in the universe to supply the rocket propellant you’d need.
So let’s step up to next possibilities, nuclear rockets with a predicted performance that’s 10 to 20 times better!
Well...it’s still not looking all that good. For a fission rocket you would need a BILLION SUPERTANKER size propellant tanks to get you there, and even with fusion rockets you would still need a THOUSAND SUPERTANKERS!
Even if we look at the best conceivable performance that we could engineer based on today’s knowledge, say an Ion engine or an antimatter rocket whose performance was 100 times better that the shuttle engines, we would need about ten railway tanker sized propellant tanks.
That doesn’t sound too bad, until you consider that we didn’t bring along any propellant to let us stop when we get to the other star system...or if we want to get there quicker than 9 centuries.
Once you add the desire to actually stop at your destination, or if you want to get there sooner, you’re back at the incredible supertanker situation again, even for our best conceivable rockets.
In conclusion, we’d really like to have a form of propulsion that doesn’t need any propellant! This implies the need to find some way to modify gravitational or inertial forces or to find some means to push against the very structure of spacetime itself."
The rest of the website[2] has some good information, even if the organization is a bit disjoint.
[1]: http://www.nasa.gov/centers/glenn/images/content/84509main_w...
[2]: http://www.nasa.gov/centers/glenn/technology/warp/ipspaper.h...
Granted, even with fusion bombs there is still a limit to how much energy and momentum you can extract from a certain mass, so the same concerns of diminishing returns apply. But according to Dyson's numbers, a 133 year trip to Alpha Centauri might be possible[1].
Even discounting interstellar travel, a trip time of only a few weeks to Mars with current technology sure sounds interesting to me.
[1] http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi...
If you read the through the material on that site you will see they are familiar with Orion. While the public oriented site glosses over details, the companion site will provide you with papers with rigorous detail.
There is no escaping it: for practical interstellar travel, we must develop massless drive or some form of spacetime manipulation that changes the mass requirements.
I can imagine you'd ride a rocket to the moon, and then the real spaceship is launched this way for inter planetary travel. It'd be like the old days of ocean liners, you stay on it for months on end, and a ship flies out may be once every year or so.
