Well, that would be one of the items to research, wouldn’t it?
You don’t research an Audi 4’s motor straightaway when the best power source you have is a waterwheel, but if you have the idea of a chariot that moves under mechanical power, you may invent the steam locomotive. From there to the A4 it’s a loooooooooot of incremental steps.
About 200 years. Not that long, relatively speaking.
http://boards.straightdope.com/sdmb/showthread.php?t=630546&highlight=harold+white+warp
For an earlier thread on this.
Understood. But since they’re setting up a microscopic experiment, are they using something along the lines of the Casimir Effect, see what they see, and announce, “Yep, this’ll work once we can create some negative mass the size of Texas. Oh, and negative mass is still only conjecture.”?
What is negative mass, anyway? Does it have negative weight? Would Earth’s gravity repel it?
From post #15 in the above linked thread on this project:
So, White’s plan is to build some toroidal interferometer using strictly positive energy to create a “warp field.” Then Lumpy suggests that the experiment is to see if they can detect a volume of negative energy, and the thread ends.
Can any physicists weigh in on this one? PDF Link.
Yeh, that’s the prediction anyhow.
It’s like anti-matter, except it’s not the charges that are reversed, it’s their masses.
How’d you like to go bowling with a -7 kg ball?
I think you use that as your second ball after a strike - and it sets all the pins back up for the next player.
BREAKING NEWS: Houston, TX — NASA, in search of interstellar warp propulsion technology, revolutionizes the recreational field of Bowling…
I will say, the paper invokes some really kickass starship designs (though, horribly executed artistically).
They just have to find a guy named Sulu for the first crew so that the captain can say “Warp speed, Mr. Sulu.”
“So what” is that having demonstrated some theoretical capability for superluminal transit is a far cry from being beamed up to your anachronistically named spaceship and zipping off to Zeta Reticuli. The innovations necessary just to support regular Earth-to-orbit travel, much less crewed interplanetary travel are far greater than those necessary to build the interstage highway system or even the Internet, and practically speaking will probably have to follow the ability to extract and manufacture complex structures in situ using space resources.
As previously noted the Alcubierre metric is a perfectly workable solution to the Einstein field equations…which does not mean that it is physically realizable, just as there are many other solutions which are obviously not valid. Without a theory of quantum gravity it isn’t even possible to say whether this metric is actually possible or if there is some limitation that would prevent the condition from emerging, and of course, the requirement for negative energy to create or control such a metric in spacetime posits a material that we don’t even know exists (or if it does exist, if it is stable enough to use for this purpose).
So, it’s an interesting experiement (to look for signs of a negative vacuum energy field) but actually turning it into a workable system for superluminal travel is about as plausible at this point as raising your Aunt Sadie from the dead.
Stranger
Yes, that seems to be what they’re doing. Basically, the experiment is supposed to detect whether the Casimir Effect causes a measurable “warping” effect. To do that they fire off a beam from a laser, split it, so that half of it will take a regular path and the other half go through the space that is supposedly warped by the capacitors. If it was indeed warped there would be a measurable phase shift in the beam.
A couple of important notes, though:
And something else about these “warp drives”: Here is a paper that shows that even if you could somehow build them, due to quantum effects, they would likely still be realistically limited to effective overall speeds of less than c: Semiclassical instability of dynamical warp drives
And then there is the whole time travel paradoxes thing, although I guess that by itself doesn’t mean it’s impossible. (who needs causality anyway?)
So what is your point, Stranger On A Train? That they are wasting their time because it will be too much effort if they are successful, or because it might not even work?
Frankly, I think NASA could use a little bit more necromancy.
Starting with the Space Shuttle . . .
What I got from it, that it’s an experiment worthwhile doing “for the science of it”, but don’t hold your breath otherwise. And that even if we prove Warp Drive is possible, we are barely in the earliest stages of creating true deep-space craft. Newton’s Laws explained reaction-propelled flight and orbital mechanics in the 1600s but it took until the 1950s to have practical launch boosters.
Define “repel”. If you have an object with negative mass, the gravitational force on it from the Earth will be upwards… However, since mass also shows up in the relationship between force and acceleration (F = ma), an upward force on such an object would cause it to accelerate downwards, just like a normal object.
Let’s take this further. Suppose you had an object made out of two pieces: One end of it (let’s say the right one) is normal matter, while the other end (the left) is negative matter. There will be a gravitational force between the two objects, pointed outward. This force will cause the positive half to accelerate to the right… And will also cause the negative half to accelerate to the right. So the whole thing will just go flying off.
Though really, we have to ask just what it is that we mean when we say the word “object”, at all. An object is a whole bunch of particles held together by forces, right? But what does that mean for the forces when the particles are all negative mass? If the particles attract each other such as opposite charges, they’ll accelerate apart. If they’re going to hold together, they all need to be the same charge. Which itself would be a big deal, because any macroscopic collection of charges all of the same sign is going to be an absolutely ludicrous amount of charge. But then, the forces get larger the closer together you get, and when the forces get larger, these particles just accelerate towards each other all the more. Such an object would collapse to zero size, near instantly.
I could go on, but the point is that negative mass is really, really weird. So weird that, if any existed, we could be really confident that we could detect it: Something that weird would be impossible to miss. It’d be like Where’s Waldo, but with Waldo wearing a day-glo safety vest and blinking lights.
Would the rubber sheet analogy be of any use for visualizing this? That is, instead of having a “depression” in spacetime to sort of mimic gravity, instead you have a hump?
No, just that it is highly speculative research (at best), and even if the phenomenon of negative vacuum pressure is demonstrated to exist, it doesn’t mean that the ability to create a field strong or broad enough to move a mass large enough to transport a useful payload, nor that the other technology and infrastructure to support the transport of a human crew across interplanetary or interstellar distances over durations of months or years.
What you would have is the material of the sheet being compressed and foreshortened in the direction of travel, such that the effective distance between the object and the destination is shorter.
Stranger
Functional launch boosters. We have yet to create a practical launch system, in terms of any sort of cost/benefit analysis of space exploration.