Sisyphus

Sort of. The Meissner effect is the phenomenon of superconductors being perfectly diamagnetic, i.e. that they repel and are repelled by magnetic fields to the point where there can be no magnetic field inside them. This can be taken advantage of to suspend them in air (at the point where the local field is weakest, for example), but levitation is not the direct result. I don't know how this would work. Are they electromagnets? I don't think a superconductor can just "give off" magnetic fields without some kind of current. Whole boulders could be levitated in a strong enough external field, sure. Caveat: I haven't even seen this movie.

The "wind turbines kill lots of birds" thing is indeed a myth: http://www.treehugger.com/files/2006/04/common_misconce.php http://www.awea.org/faq/sagrillo/swbirds.html For perspective, the average avian mortality rate per modern turbine is less than 2 per year. By contrast, 60-80 million birds are killed by being hit by cars every year, and anywhere between 100 million and 1 billion are killed by flying into windows.

Hey, I like Star Trek, too, but it's much more than just little things. The way Star Trek spaceships operate and travel and fight much more closely resembles 18th century sailing ships than anything actually in space, let alone 24th century (or whatever) tech. Or how almost every planet is apparently the size of a small town. Or how the technology of pockets has been inexplicably lost. But that's fine. It's fantasy.

I think if the writers of Star Wars or Star Trek claimed they were "doing it all with [real] physics," they would be mocked much more heartily than anyone is mocking you here.

Yup: http://en.wikipedia.org/wiki/Eco-terrorism Although "terrorism" is such a widely abused and loaded term that it's practically meaningless anyway.

No, you increase the velocity by 5 meters per second, you're just going to have a very, very slightly larger and more eccentric orbit. It's a question of kinetic and potential energy. You can convert one into the other readily enough, but you can't increase the sum of both without some kind of external source. The kinetic energy in this case comes from the Earth's velocity, specifically (1/2)mv^2, where m is the Earth's mass and v is it's velocity relative to the sun. The potential energy comes from the "height" in the gravity well of the sun. To throw a ball in the air, you give it velocity. This velocity is used up, and at the peak of its trajectory it stops, and it falls back down again and lands with a high velocity again. This is just converting velocity to height and back again, or kinetic to potential and back again. What's true of a ball in the Earth's gravity is exactly the same as the Earth in the Sun's gravity. To get it to move further away, you need to add energy. Now, the amount of energy needed to gain height decreases the farther away you are, because the strength of the gravitational field decreases. In fact, there is only a finite amount of energy needed to escape completely. That's what I calculated, minus the kinetic and potential energy the Earth already has. And we come up short by 900 billion times the annual energy usage of human beings.

Why would I be upset about that? (Sorry if I gave that impression.) You asked if if it was acceptable, I showed that it wasn't. The calculation is for the difference in between the Earth's current kinetic energy and the energy that it would have at the bare minimum velocity needed to escape the solar system. That is the absolute minimum energy you will need allowable by the laws of physics, whether it's added all at once (which would obviously kill everybody) or over thousands of years (which might still kill everybody, I don't have enough info). What methods you employ can't get around that, they can only approach it as a 100% efficient goal. I didn't say you can't change the Earth's velocity. Jumping in the air changes the Earth's velocity, and falling back down changes it back. Launching something on an escape orbit even changes it permanently. The question is changing it enough. And that's actually quite simple to calculate. As for earthquakes, etc.: Certainly you can generate little enough thrust to not, say, shatter every continental plate (more than a building code issue). But how quickly do you want to accelerate? How much time does the Earth have to get out of the way? That will determine how much acceleration and thus how much thrust you need.

Euclid takes 47 propositions to prove it from first principles, but those are real proofs. You can show it intuitively with a single picture, as shown at "proof #9" at this link: http://www.cut-the-knot.org/pythagoras/index.shtml

Heh, no, I'm not familiar with that. Yeah, I immediately thought of Puppeteers, too. Niven had the main planet kept warm just from waste heat of their civilization, and mini "fusion balls" orbiting the farming worlds as artificial suns, IIRC. I also don't seem to remember it being explained exactly how they got everything moving in the first place, though at least he recognized the magnitude of the feat to make Louis Wu suitably awed by it. I've only read the first two Ringworld books, but as of the second one actually moving the whole thing was mentioned as a theoretical possibility. Though an extremely impractical one - it would cause havoc with the sun, have to have very small acceleration to avoid leaving the ring behind, and be damn hard to steer. Merged post follows: Consecutive posts merged No, not acceptable. It's just a matter of magnitude. I'll repeat my calculation above, that the minimum energy needed is 900,000,000,000 times our current yearly capacity. 60 times the age of the universe worth of energy consumption at our current rate, to frame it another way. And "realistically," it would probably be a lot more than that. There just isn't anywhere near enough energy available, not in the entire Earth. That's the main problem, but there are others. Have you figured out how much thrust you need per acceleration, taking into account the Earth's own gravity pulling exhaust back? And have you figured out how much acceleration is possible without, for example, earthquakes big enough to kill everybody?

Yes, stopping would be an issue. Incoming from outside Alpha Centauri's solar system, we would necessarily have a higher than escape velocity by the time we arrived. And we wouldn't necessarily get there "eventually." I mean, on a long enough timeline we'd get anywhere, but presumably we want there to get there before our new sun fizzles out.

Everything I can.

BTW, just did some rough calculations. The amount of energy needed to get the Earth up to escape velocity for the solar system would be about 4.3*10^32 joules (that is, to add to our current orbital velocity, which assumes we're trying to go somewhere on our current orbital plane, which we aren't), which is approximately 900 billion times the total energy consumption of everyone on Earth in 2008. Of course, that's just escaping the solar system. That's not to get moving fast enough to actually ever get there. Or, you know, stop.

Everything would die. Basically you would need a habitat as protected and self-sufficient as you would need to live permanently in interstellar space. Because that's where you'd be (just stuck to a giant frozen rock where we all used to live). But I'm still wondering how we're moving the Earth in the first place, as that would probably determine conditions.

::silently looks over thread with a single arched eyebrow::

I don't see what planetary-scale venereal burning would accomplish, and I certainly don't think it's any way to start a new life around Alpha Centauri.

Did you read post #20?

Don't worry about any of that. You could keep the Earth plenty warm with the same magic infinite energy source you use to move it in the first place.

tl;dr

What if, indeed? There are fundamental limits, imposed by the laws of physics themselves, to how small and how large we can see. So if there was a "miniature universe" within every elementary particle, we would have no way of knowing, and it would have no effect on us. More or less, yeah. But what does that have to do with the first two sentences? Not just that. There's nothing in the Many Worlds Interpretation that indicates special status to "choices" by things that can think. Every particle that can zig or zag actually does both. Whoooaa, now. If there is a multiverse, you wouldn't be able to "travel between."

In addition to looking for reasons why it isn't true, you should reexamine the reasons for why you think it might be. For example, your reasoning seems to be that because there are other things that can be too large to be stabile, black holes can be too large to be stabile. But that doesn't logically follow. There are specific reasons why stars go nova (i.e., the physical laws in play are not "some things are too big to live"), and those reasons don't apply to black holes. There is no known mechanism that might make an upper size limit on black hole stability, and you're not proposing one, either. Just asserting that one exists. And that's just one hypothesis. You've made several others, and I don't see how each follows from the next. Black holes will "merge," the proposed "upper limit" on mass just happens to be the same as the combined mass of the observable universe, etc. You're offering not one hypothesis, but many unrelated ones (or at least you don't offer a relationship), and don't really support any of them. Because you don't give reasons, there is no reasoning to evaluate.

What?

I got through college by choosing to be correct. Seriously, though, why are we still talking about this? MT is mass*time. That is its meaning. It's not terribly useful. There is not a special word in the English language for it besides mass*time. What is in dispute? By contrast, MD/T means mass*distance/time. That is it's meaning. It is a useful quantity, and has a special word for it in English (though not every language): "momentum."

"Anything that provides nutritional support?" OK: Water that is in something that provides nutritional support is not magically not water. Corrollary: 100% pure water is not the only water that "counts."

I don't disagree that that's good advice. But the act of chewing does not magically make water turn into something else. So if "food" is a "anything that involves chewing," then the statement is not - cannot be - technically accurate.

But again, keeping a plane in the air is different than hovering a massive object with brute force. Aircraft have wings for lift and aren't directly opposing gravity, and every aspect of their design is geared towards minimizing weight, but it still takes huge amounts of fuel. And nuclear power is used in vehicles. Most naval vessels are nuclear powered. It works great, but it's not enough power to get them to hover in the air! In fact, why not use that as an example for some rough calculations. Compare to a real-life nuclear-powered "floating airport:" an aircraft carrier. Wikipedia says the Nimitz class are about 101,000 long tons, or 102620738kg. Let's round down to an even 100000000kg. To directly oppose gravity, you need enough force to accelerate 100000000kg at 9.8m/s/s. Eh, round up to ten. So, the gravitational force on an aircraft carrier is about 1 billion newtons. For comparison, the Saturn V engine, the most powerful rocket engine ever (that powered the Apollo rockets), had a maximum thrust of 34 million newtons, and fired for six minutes. So what you want is the thrust of about 30 Saturn V rockets, firing permanently. And that is why we don't have huge, permanently hovering, heavier than air structures.