Alcubierre warp drive

[Humabout]

Originally Posted by doctorevilbrain

How could a spaceship go through a Wormhole smaller than the width of a proton without being destroyed? I don't get it. It doesn't make sense. The link above doesn't work anymore.

Not sure if this helps you at all with understanding Alcubierre's idea, but here's his actual paper on it.

[MrTim]

Originally Posted by doctorevilbrain

How could a spaceship go through a Wormhole smaller than the width of a proton without being destroyed? I don't get it. It doesn't make sense.

I think this covers it:

Originally Posted by lwcamp

(since you presumably want to warp a spacecraft, you put the spacecraft in the sub-universe and use the wormhole to get in and out - presumably you have some way of expanding the wormhole at your trip origin and destination).

[doctorevilbrain]

I read the paper. I understood most of the words, but the math means nothing to me. It might as be written in Martian for all it means to me. Please explain to me what it means in words. Why can't people just use words? I still don't understand how a spaceship could go into a wormhole without being crushed by gravity and everybody getting killed. I had to look up some words that I didn't understand.

[Anaraxes]

Please explain to me what it means in words

Not that I understand the math myself, either, but I believe the suggestion was to design a drive system that uses a wormhole that you can make larger or smaller.

So:
(1) Create your pocket universe (in this context, I'd really rather call it "subspace" for obvious reasons :) with a big wormhole to normal space;
(2) Move the ship into subspace through the big wormhole;
(3) Shrink the wormhole to tiny size;
(4) Warp somewhere, enjoying the benefits of your not-quite-entire-bubble with tiny connection;
(5) At your destination, expand the wormhole again to get the ship out of subspace and back into normal space.

[Humabout]

Originally Posted by doctorevilbrain

I read the paper. I understood most of the words, but the math means nothing to me. It might as be written in Martian for all it means to me. Please explain to me what it means in words.

In Words

Originally Posted by doctorevilbrain

Why can't people just use words?

Because math is the language of science.

Originally Posted by doctorevilbrain

I still don't understand how a spaceship could go into a wormhole without being crushed by gravity and everybody getting killed. I had to look up some words that I didn't understand.

You are creating a bubble of compressed spacetime. The best way I can think to explain this is to think of a number line:

|..........|..........|..........|..........|..... .....|..........|..........|

Each tick is a gradation on the number line. You might have something that has a dimension of 3 ticks:
.......................___________________
|..........|..........|..........|..........|..... .....|..........|..........|

Now you might use some exotic material or some such to compress spacetime locally, decreasing the space between ticks, but retaining the length of in number of ticks:

......................____________
|..........|.........|......|......|......|....... ..|..........|

The line is still 3 ticks long. It is still in the same location: starting at the third tick. The space it exists within is simply curved so that, relative to the rest of the space, the line is shorter without actually changing any of the line's properties - it remains 3 ticks long.

Compress your bubble small enough, and it just might fit through your wormhole.

Incidentally, this is the way in which spacetime is already curved by gravity. This probably isn't the best analogy, but it's better than just throwing out a trite "compress spacetime" as an answer. I hope it helps.

[MrTim]

Originally Posted by Humabout

9

Because math is the language of science.

Also because it often takes a *lot* longer to say with words. Compare "Energy equals mass times the square of the speed of light" to "e=mc^2"; that's a very simple bit of math to put into words, and it still takes almost eight times as many characters.

[doctorevilbrain]

I did understand it in words. I don't care that math is the language of science, it's extremely elitist. Alan Alda is right when he says that scientists can't communicate with average people. But I still don't know how the warp bubble can shrink and fit into a wormhole. The paper written by Alcubiere doesn't mention how to shrink it.

[MrTim]

Originally Posted by doctorevilbrain

I did understand it in words. I don't care that math is the language of science, it's extremely elitist.

The problem is that in order to properly do science you very often need the math. It's a necessary part of both testing hypotheses and developing speculative models. It also cuts across international barriers; everyone who understands the math can understand an equation, regardless of the language they speak.

Imagine talking about GURPS without using any GURPS terms. Possible in some cases, yes, and even necessary starting out. But if you're getting into a discussion of, say, whether modifiers for Appearance apply to Fast Talk rolls, it would certainly expend a lot of time and effort and would probably not be possible. I don't see how that's "elitist."

Alan Alda is right when he says that scientists can't communicate with average people.

Not that I disagree (and his annual contest to explain a scientific concept in layman's terms is a spectacular idea), but I don't think the average person is very good at talking about their job or hobby to outsiders.

But I still don't know how the warp bubble can shrink and fit into a wormhole. The paper written by Alcubiere doesn't mention how to shrink it.

That wasn't in the paper. That was something come up with later (possibly by lwcamp in this very thread) to make the revised version of Alcubierre's hypothesis workable as a means of transport.

[Agemegos]

Originally Posted by doctorevilbrain

Why can't people just use words?

It's because mathematical expressions are designed to denote the sorts of relationships among their elements that turn out to be important in physics (and some other sciences), whereas sentences, being linear, are not. That makes it much, much easier to describe those sorts of relationships in explicit detail, unambiguously, and compactly if you use an mathematical expression.

[Humabout]

Originally Posted by doctorevilbrain

I did understand it in words. I don't care that math is the language of science, it's extremely elitist.

It's hardly elitist to use the tools of your trade to practice your trade. That paper is one scientist speaking to other scientists about their trade. Would you expect your doctor to converse with your surgeon about your operation using phrases like "the vein is the one on the inside of his forearm, but not the big one. The little one that tucks under the inside of his elbow and branches three times before reaching his wrist. You're going to have to put the balloon thingy in there to break the wall of blood, but make sure no bits get in his noggin because then he might get brain-bleeding and die."

As for physics using mathematics to explain things, it's because math lets you lay out definite and concise relationships and, more importantly, make predictions that can later be tested. Words don't do this.

For example:

"Gravity only acts downward"
"An object in motion stays in motion until otherwise acted upon by a force"
"Acceleration is the time-rate change of velocity"
"Velocity is the time-rate change of position"

That's four bits of rudimentary high school physics in words. Now tell me how far downrange a shell fired with a muzzle velocity of 800 m/s at an elevation angle of 23 degrees while sitting on a 12-foot-high hill above a plain, neglecting friction. You can't without using math:

d = [v^2/(2g)]*[1+sqrt(1+(2gh)/(v^2*sin^2(theta)))].

And you can't get that formula, if you don't first describe gravity mathematically: g = -gj = [dv/dt]*j, velocity mathematically: v = x_doti + y_dotj = ds/dt, and finding useful relationships between them:

v_f^2 = v_i^2+2as
s_f = s_i + vt + 0.5at^2
v_f = v_i + at

Now you can actually start to dig into science. And if this process seems difficult, all I can say is that there's probably a reason some jobs require more schooling than others. If you put in the time to learn some basic math, you can follow a great deal of physics, and the bits that require stuff like set theory, tensor calculus, and differential geometry aren't readily explained in anything less than broad brush strokes.

Originally Posted by doctorevilbrain

The paper written by Alcubiere doesn't mention how to shrink it.

His paper isn't about shrinking things. It's about a means of superluminal travel.